From a5d93aa27f76b9b45d4c50448867630695fceda4 Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Fri, 15 Nov 2024 13:21:43 +0100
Subject: [PATCH 01/12] update messages

---
 .../complexity/RedundantBooleanEqual.java     |   2 +-
 .../complexity/UseOperatorAssignment.java     |   8 +-
 .../core/check/debug/AssertCheck.java         |   2 +-
 .../check/general/StringCompareCheck.java     |   7 +-
 .../core/check/general/UseGuardClauses.java   | 111 ----------------
 .../src/main/resources/strings.de.ftl         | 121 +++++++++---------
 .../src/main/resources/strings.en.ftl         | 108 ++++++++--------
 .../UseGuardClauses/code/Test.java            |  89 -------------
 .../check_tests/UseGuardClauses/config.txt    |   8 --
 9 files changed, 130 insertions(+), 326 deletions(-)
 delete mode 100644 autograder-core/src/main/java/de/firemage/autograder/core/check/general/UseGuardClauses.java
 delete mode 100644 autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/UseGuardClauses/code/Test.java
 delete mode 100644 autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/UseGuardClauses/config.txt

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/RedundantBooleanEqual.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/RedundantBooleanEqual.java
index ac09ffdf..ae53acea 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/RedundantBooleanEqual.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/RedundantBooleanEqual.java
@@ -35,7 +35,7 @@ private void reportProblem(CtBinaryOperator<?> ctBinaryOperator, boolean literal
         addLocalProblem(
             ctBinaryOperator,
             new LocalizedMessage(
-                "redundant-boolean-equal",
+                "common-reimplementation",
                 Map.of(
                     "suggestion", suggestion
                 )
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/UseOperatorAssignment.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/UseOperatorAssignment.java
index 69958075..ec5f0a88 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/UseOperatorAssignment.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/UseOperatorAssignment.java
@@ -5,6 +5,7 @@
 import de.firemage.autograder.core.check.ExecutableCheck;
 import de.firemage.autograder.core.integrated.IntegratedCheck;
 import de.firemage.autograder.core.integrated.StaticAnalysis;
+import de.firemage.autograder.core.integrated.TypeUtil;
 import de.firemage.autograder.core.integrated.evaluator.OperatorHelper;
 import spoon.processing.AbstractProcessor;
 import spoon.reflect.code.BinaryOperatorKind;
@@ -39,8 +40,7 @@ public class UseOperatorAssignment extends IntegratedCheck {
     private boolean isCommutativeType(CtTypedElement<?> ctTypedElement) {
         return ctTypedElement.getType() == null
                || NON_COMMUTATIVE_TYPES.stream()
-                                       .map(ty -> ctTypedElement.getFactory().Type().createReference(ty))
-                                       .noneMatch(ty -> ty.equals(ctTypedElement.getType()));
+                                       .noneMatch(ty -> TypeUtil.isTypeEqualTo(ctTypedElement.getType(), ty));
     }
 
     private boolean isCommutative(BinaryOperatorKind binaryOperatorKind) {
@@ -106,8 +106,8 @@ public void process(CtAssignment<?, ?> assignment) {
                     addLocalProblem(
                         assignment,
                         new LocalizedMessage(
-                            "use-operator-assignment-exp",
-                            Map.of("simplified", simplifiedExpr)
+                            "common-reimplementation",
+                            Map.of("suggestion", simplifiedExpr)
                         ),
                         ProblemType.USE_OPERATOR_ASSIGNMENT
                     );
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/debug/AssertCheck.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/debug/AssertCheck.java
index cceec3e1..84ae76af 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/debug/AssertCheck.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/debug/AssertCheck.java
@@ -15,7 +15,7 @@ protected void check(StaticAnalysis staticAnalysis) {
         staticAnalysis.processWith(new AbstractProcessor<CtAssert<?>>() {
             @Override
             public void process(CtAssert<?> element) {
-                addLocalProblem(element, new LocalizedMessage("assert-used-exp"), ProblemType.ASSERT);
+                addLocalProblem(element, new LocalizedMessage("assert-used"), ProblemType.ASSERT);
             }
         });
     }
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/general/StringCompareCheck.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/general/StringCompareCheck.java
index 56f1ee98..ba5f1270 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/general/StringCompareCheck.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/general/StringCompareCheck.java
@@ -35,8 +35,11 @@ public void process(CtBinaryOperator<?> operator) {
 
                 if (isStringComparison(lhs, rhs)) {
                     addLocalProblem(operator, new LocalizedMessage(
-                            "string-cmp-exp",
-                            Map.of("lhs", lhs, "rhs", rhs)
+                            "suggest-replacement",
+                            Map.of(
+                                "original", operator.toString(),
+                                "replacement", "%s.equals(%s)".formatted(lhs, rhs)
+                            )
                         ),
                         ProblemType.STRING_COMPARE_BY_REFERENCE
                     );
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/general/UseGuardClauses.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/general/UseGuardClauses.java
deleted file mode 100644
index 10b737d5..00000000
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/general/UseGuardClauses.java
+++ /dev/null
@@ -1,111 +0,0 @@
-package de.firemage.autograder.core.check.general;
-
-import de.firemage.autograder.core.LocalizedMessage;
-import de.firemage.autograder.core.ProblemType;
-import de.firemage.autograder.core.check.ExecutableCheck;
-import de.firemage.autograder.core.integrated.FactoryUtil;
-import de.firemage.autograder.core.integrated.IntegratedCheck;
-import de.firemage.autograder.core.integrated.StatementUtil;
-import de.firemage.autograder.core.integrated.StaticAnalysis;
-import de.firemage.autograder.core.integrated.effects.Effect;
-import de.firemage.autograder.core.integrated.effects.TerminalEffect;
-import spoon.processing.AbstractProcessor;
-import spoon.reflect.code.BinaryOperatorKind;
-import spoon.reflect.code.CtExpression;
-import spoon.reflect.code.CtIf;
-import spoon.reflect.code.CtStatement;
-import spoon.reflect.code.UnaryOperatorKind;
-
-import java.util.List;
-import java.util.Optional;
-
-@ExecutableCheck(reportedProblems = { ProblemType.USE_GUARD_CLAUSES })
-public class UseGuardClauses extends IntegratedCheck {
-    private void reportProblem(CtStatement ctStatement, CtExpression<?> condition) {
-        addLocalProblem(
-            ctStatement,
-            new LocalizedMessage("use-guard-clauses"),
-            ProblemType.USE_GUARD_CLAUSES
-        );
-    }
-
-    private boolean isTerminal(CtStatement ctStatement) {
-        List<CtStatement> ctStatements = StatementUtil.getEffectiveStatements(ctStatement);
-
-        if (ctStatements.isEmpty()) return false;
-
-
-        Optional<Effect> optionalEffect = StatementUtil.tryMakeEffect(ctStatements.get(ctStatements.size() - 1));
-
-        return optionalEffect.map(TerminalEffect.class::isInstance).orElse(false);
-    }
-
-    private void checkCtIf(CtIf ctIf, CtExpression<?> condition) {
-        // if the condition != null, then the ctIf is an else if
-        if (condition != null) {
-            CtExpression<?> ifCondition = FactoryUtil.createBinaryOperator(
-                condition,
-                ctIf.getCondition(),
-                BinaryOperatorKind.AND
-            );
-
-            if (this.isTerminal(ctIf.getThenStatement())) {
-                reportProblem(ctIf.getThenStatement(), ifCondition);
-            }
-        }
-
-        // the condition to reach the else statement
-        CtExpression<?> elseCondition = FactoryUtil.createUnaryOperator(
-            UnaryOperatorKind.NOT,
-            ctIf.getCondition()
-        );
-
-        // check the else statement
-        CtStatement ctStatement = ctIf.getElseStatement();
-        // if there is no else, return
-        if (ctStatement == null) return;
-
-        List<CtStatement> ctStatements = StatementUtil.getEffectiveStatements(ctStatement);
-
-        if (condition != null) {
-            elseCondition = FactoryUtil.createBinaryOperator(
-                condition,
-                elseCondition,
-                BinaryOperatorKind.AND
-            );
-        }
-
-        if (ctStatements.size() == 1 && ctStatements.get(0) instanceof CtIf ctElseIf) {
-            CtExpression<?> elseIfCondition = FactoryUtil.createBinaryOperator(
-                elseCondition,
-                ctElseIf.getCondition(),
-                BinaryOperatorKind.AND
-            );
-
-            checkCtIf(ctElseIf, elseIfCondition);
-            // check the else statement
-        } else if (this.isTerminal(ctStatement)) {
-            reportProblem(ctStatement, elseCondition);
-        }
-    }
-
-    @Override
-    protected void check(StaticAnalysis staticAnalysis) {
-        staticAnalysis.processWith(new AbstractProcessor<CtIf>() {
-            @Override
-            public void process(CtIf ctIf) {
-                if (ctIf.isImplicit() || !ctIf.getPosition().isValidPosition()) return;
-
-                CtIf parentIf = ctIf.getParent(CtIf.class);
-                if (parentIf != null && parentIf.getElseStatement() != null) {
-                    List<CtStatement> ctStatements = StatementUtil.getEffectiveStatements(parentIf.getElseStatement());
-                    if (ctStatements.size() == 1 && ctStatements.get(0).equals(ctIf)) {
-                        return;
-                    }
-                }
-
-                checkCtIf(ctIf, null);
-            }
-        });
-    }
-}
diff --git a/autograder-core/src/main/resources/strings.de.ftl b/autograder-core/src/main/resources/strings.de.ftl
index 838667a3..1727da12 100644
--- a/autograder-core/src/main/resources/strings.de.ftl
+++ b/autograder-core/src/main/resources/strings.de.ftl
@@ -24,18 +24,18 @@ common-reimplementation = Der Code kann vereinfacht werden zu '{$suggestion}'.
 use-string-formatted = '{$formatted}' ist schöner zu lesen.
 use-format-string = '{$formatted}' ist schöner zu lesen.
 
-optional-tri-state = Statt einem Optional boolean, sollte man ein enum verwenden.
+optional-tri-state = Statt einem Optional boolean, sollte ein enum verwendet werden.
 
 equals-hashcode-comparable-contract = Es müssen immer equals und hashCode zusammen überschrieben werden. Genauso muss wenn Comparable implementiert wird equals und hashCode überschrieben werden.
 
-use-enum-collection = Bei Maps wenn ein Enum als Key ist und bei Sets als Wert, sollte man EnumMap/EnumSet verwenden.
+use-enum-collection = Verwende bei Maps mit enum als Key oder bei sets als Wert EnumMap/EnumSet.
 
 compare-to-zero = Das Ergebnis von compareTo oder compare sollte nur mit 0 verglichen werden.
-                Es ist eine Implementierungsdetail, ob ein gegebener Typ streng die Werte
+                Es ist ein Implementierungsdetail, ob ein gegebener Typ die Werte
                 '-1, 0, +1' oder andere zurückgibt.
 equals-using-hashcode = Equals nur mit hashCode zu implementieren ist fehleranfällig.
-                        Hashes kollidieren häufig, was zu falschen Ergebnissen in equals führt.
-equals-unsafe-cast = Im Javadoc von equals steht, dass es false für inkompatible Typen zurückgeben soll.
+                        Hashes können kollidieren, wodurch es zu falschen Ergebnissen in equals kommen könnte.
+equals-unsafe-cast = Im JavaDoc von equals steht, dass es false für inkompatible Typen zurückgeben soll.
                     Diese Implementierung kann eine ClassCastException werfen.
 equals-incompatible-type = Ein Vergleich zwischen Objekten mit inkompatiblen Typen gibt immer false zurück
 inconsistent-hashcode = Das hashCode-Verhalten ist inkonsistent. Es wird in equals nicht verglichen, aber in hashCode verwendet.
@@ -47,7 +47,7 @@ equals-reference = == sollte in equals verwendet werden, um Gleichheit zu sich s
 array-as-key-of-set-or-map = Arrays überschreiben weder equals noch hashCode. Dementsprechend werden Vergleiche basierend
                             auf der Referenz gemacht und nicht auf dem Inhalt. Verwende stattdessen eine Liste.
 
-implement-comparable = Der Typ '{$name}' sollte `Comparable<{$name}>` implementieren, dann kann man sich den `Comparator` sparen.
+implement-comparable = Der Typ '{$name}' sollte 'Comparable<{$name}>' implementieren, dann kann man sich den 'Comparator' sparen.
 
 # Comment
 commented-out-code = Dieser auskommentierte Code sollte entfernt werden
@@ -58,24 +58,24 @@ comment-language-exp-german = Der Code enthält deutsche und englische Kommentar
 
 unnecessary-comment-empty = Dieser Kommentar ist leer und sollte daher entfernt werden
 
-javadoc-method-exp-param-missing = Der Parameter '{$param}' wird im Javadoc-Kommentar nicht erwähnt
-javadoc-method-exp-param-unknown = Der JavaDoc-Kommentar erwähnt den Parameter '{$param}', dieser wird allerdings nicht deklariert
+javadoc-method-exp-param-missing = Der Parameter '{$param}' wird im JavaDoc nicht dokumentiert.
+javadoc-method-exp-param-unknown = Der JavaDoc dokumentiert den nicht existierenden Parameter '{$param}'.
 
 javadoc-unexpected-tag = Der JavaDoc-Kommentar sollte keinen '@{$tag}'-Tag haben.
 
-javadoc-type-exp-invalid-author = Im @author-Tag sollte dein u-Kürzel stehen: {$authors}
+javadoc-type-exp-invalid-author = Im @author-Tag sollte ein u-Kürzel stehen: {$authors}
 
-javadoc-stub-exp-desc = Die Beschreibung des Javadoc-Kommentars ist leer
+javadoc-stub-exp-desc = Die Beschreibung des JavaDoc-Kommentars ist leer
 javadoc-stub-exp-param = Nichtssagende Beschreibung für den Parameter '{$param}'
 javadoc-stub-exp-return = Nichtssagende Beschreibung für den Rückgabewert
-javadoc-stub-exp-throws = Nichtssagende Beschreibung für die Exception {$exp}
+javadoc-stub-exp-throws = Nichtssagende Beschreibung für die Exception '{$exp}'
 
-javadoc-undocumented-throws = Die Exception {$exp} wird geworfen, aber nicht im Javadoc-Kommentar erwähnt.
+javadoc-undocumented-throws = Die Exception '{$exp}' wird geworfen, aber nicht im JavaDoc-Kommentar erwähnt.
 
 todo-comment = TODOs sollten nicht in der finalen Abgabe vorhanden sein.
 
 # Complexity
-use-diamond-operator = Du kannst die Typen in '< A, B, ... >' entfernen und stattdessen '<>' verwenden, siehe https://docs.oracle.com/javase/tutorial/java/generics/genTypeInference.html und https://stackoverflow.com/a/16352848/7766117
+use-diamond-operator = Die Typen in '< A, B, ... >' können entfernt werden, schreibe stattdessen '<>'.
 
 extends-object = Explizit von Object zu erben ist unnötig
 
@@ -87,8 +87,6 @@ redundant-modifier = Die folgenden Modifier sind redundant und sollten deswegen
 
 redundant-return-exp = Unnötiges return
 
-redundant-boolean-equal = Es ist unnötig explizit zu überprüfen, ob eine Bedingung gleich true oder false ist. Schreibe stattdessen '{$suggestion}'.
-
 self-assignment-exp = Nutzlose Zuweisung von '{$rhs}' zu '{$lhs}'
 
 too-many-exceptions = Das Projekt definiert {$count} Exceptions. Das sind zu viele.
@@ -97,30 +95,27 @@ redundant-variable = Die Variable '{$name}' ist unnötig, verwende stattdessen d
 
 unused-import = Der Import '{$import}' wird nicht verwendet und sollte deswegen entfernt werden.
 
-use-operator-assignment-exp = Zuweisung kann zu '{$simplified}' vereinfacht werden
-
 complex-regex = Nichttriviale Regex brauchen einen erklärenden Kommentar (Score ist {$score}, maximal erlaubt ist {$max})
 
-redundant-catch = Eine exception sollte nicht gefangen werden, um sie dann direkt wieder zu werfen.
+redundant-catch = Eine Exception sollte nicht gefangen werden, um sie dann direkt wieder zu werfen.
 
 redundant-uninitialized-variable = Die Variable '{$variable}' wurde deklariert, aber der Wert '{$value}' wird nicht direkt zugewiesen. Schreibe stattdessen '{$suggestion}'.
 
-multiple-inline-statements = Es sollten nicht mehrere Aussagen in einer Zeile stehen. Also keine Deklarationen von mehreren Variablen oder Zuweisungen in einer Zeile.
+multiple-inline-statements = Es sollten nicht mehrere Aussagen in einer Zeile stehen.
 
-multi-threading = Multithreading ist nicht Teil der Vorlesung. Code der nur einem Thread ausgeführt wird, thread-safe zu schreiben, macht den Code unnötig komplex.
+multi-threading = Multithreading wird nicht verwendet. Code der nur auf einem Thread ausgeführt wird, thread-safe zu schreiben, macht den Code unnötig komplex.
 
-try-catch-complexity = Die Komplexität von try-catch-Blöcken sollte möglichst gering gehalten werden. Es sollten weniger als {$max} Statements vorhanden sein. Versuche den Code in mehrere Methoden aufzuteilen bzw. nicht dringend benötigte Statements aus dem try-Block zu entfernen.
+try-catch-complexity = Die Komplexität von try-catch-Blöcken sollte möglichst gering gehalten werden.
+                       Es sollten weniger als {$max} Statements vorhanden sein. Versuche den Code in
+                       mehrere Methoden aufzuteilen bzw. nicht dringend benötigte Statements aus dem
+                       try-Block zu entfernen.
 
 redundant-else = Die 'else' ist unnötig. Schreibe '{$expected}' statt '{$given}'.
 
 redundant-assignment = Der Variable '{$variable}' wird hier ein Wert zugewiesen, der dann nie verwendet wird. Deswegen kann die Zuweisung entfernt werden.
 
 # Debug
-assert-used-exp = Assertions lassen das gesamte Programm abstürzen, wenn sie false sind.
-    Außerdem können sie deaktiviert werden, weswegen man sich nicht darauf verlassen kann,
-    dass bestimmte Bedingungen zutreffen. Sie sind super für Testzwecke, sollten aber nicht
-    Teil der finalen Lösung sein. Wenn du eine Invariante dokumentieren willst, verwende
-    einen Kommentar.
+assert-used = Assertions sollten nicht in der finalen Abgabe vorhanden sein. Verwende stattdessen Exceptions.
 
 print-stack-trace = Stack Traces sollten in der Abgabe nicht ausgegeben werden
 
@@ -130,18 +125,18 @@ custom-exception-inheritance-runtime = Die selbstdefinierte Exception '{$name}'
 
 empty-catch-block = Leerer catch-Block
 
-exception-controlflow-caught = {$exception} wird geworfen und im umgebenden Block sofort wieder gefangen
-exception-controlflow-should-not-be-caught = {$exception} sollte man niemals fangen
+exception-controlflow-caught = '{$exception}' wird geworfen und im umgebenden Block sofort wieder gefangen
+exception-controlflow-should-not-be-caught = '{$exception}' sollte man niemals fangen
 
-runtime-exception-caught = RuntimeExceptions '{$exception}' sollten nicht gefangen werden
+runtime-exception-caught = RuntimeException '{$exception}' sollten nicht gefangen werden
 
 exception-message = Eine Exception sollte immer eine Nachricht dabei haben, die erklärt was der Fehler ist und im Idealfall wie es zu dem Fehler kam.
 
-number-format-exception-ignored = NumberFormatException sollte gefangen werden und entweder behandelt oder durch eine eigene Exception ersetzt werden.
+number-format-exception-ignored = 'NumberFormatException' sollte gefangen werden und entweder behandelt oder durch eine eigene Exception ersetzt werden.
 
 # General
 
-compare-objects-exp = Implementiere eine equals-Methode für den Typ {$type} und verwende sie zum Vergleichen
+compare-objects-exp = Der Typ '{$type}' sollte 'equals' implementieren und nicht über 'toString' verglichen werden.
 
 variable-should-be = Die Variable '{$variable}' sollte '{$suggestion}' sein.
 
@@ -149,29 +144,25 @@ reassigned-parameter = Dem Parameter '{$name}' sollte kein neuer Wert zugewiesen
 
 double-brace-init = Die obskure 'Double Brace'-Syntax sollte vermieden werden
 
-missing-override = '{$name}' sollte eine '@Override'-Annotation haben, siehe https://stackoverflow.com/a/94411/7766117.
+missing-override = '{$name}' sollte eine '@Override'-Annotation haben.
 
-system-specific-linebreak = Systemabhängiger Zeilenumbruch (\n) benutzt. Besser ist System.lineSeparator() oder (falls es sich um einen format-String handelt) '%n'.
+system-specific-linebreak = Systemabhängiger Zeilenumbruch (\n) benutzt. Besser ist 'System.lineSeparator()' oder (falls es sich um einen format-String handelt) '%n'.
 
 field-should-be-final = Das Attribut '{$name}' sollte final sein.
 
-string-cmp-exp = Strings sollten nicht per Referenz, sonder mit der 'equals'-Methode verglichen werden: '{$lhs}.equals({$rhs})' statt '{$lhs} == {$rhs}'
+do-not-use-raw-types-exp = Generische Typen sollten immer mit Typparameter angegeben werden und nie als Raw Type.
 
-do-not-use-raw-types-exp = Generische Typen sollten immer mit Typparameter angegeben werden und nie als Raw Type, siehe https://stackoverflow.com/a/2770692/7766117
+avoid-labels = Labels sollten vermieden werden.
 
-avoid-labels = Labels sollten vermieden werden. Siehe https://stackoverflow.com/a/33689582/7766117.
+avoid-shadowing = Die Variable '{$name}' verdeckt ein Attribut mit dem selben Namen. Abgesehen vom Konstruktor und settern, sollte man das vermeiden.
 
-avoid-shadowing = Die Variable '{$name}' verdeckt ein Attribut mit dem selben Namen. Abgesehen vom Konstruktor, sollte man das vermeiden.
-
-suppress-warnings = @SuppressWarnings unterdrückt Warnungen des Compilers oder von Checkstyle, anstatt das unterliegende Problem zu beheben.
+suppress-warnings = '@SuppressWarnings' unterdrückt Warnungen des Compilers oder Checkstyle, anstatt das unterliegende Problem zu beheben.
 
 scanner-closed = Scanner sollte geschlossen werden
 
 unchecked-type-cast = Es muss sicher gestellt werden, dass der Typ des Objekts mit dem Typ des Casts übereinstimmt. Ansonsten kann der Code abstürzen.
 
-compare-char-value = Hier wird '{$expression}' vom Typ char mit dem Wert {$intValue} verglichen. Es ist nicht offensichtlich für welchen Buchstabe der Wert steht, schreibe stattdessen '{$charValue}'.
-
-use-guard-clauses = Der Code bricht den normalen Kontrollfluss durch zum Beispiel ein return ab. if-else-Blöcke mit solchen Abbrüchen kann man mithilfe von sogenannten guard-clauses schöner schreiben. Das hat unter anderem den Vorteil, dass man doppelten Code leichter erkennt. Siehe für eine detaillierte Erklärung https://medium.com/@scadge/if-statements-design-guard-clauses-might-be-all-you-need-67219a1a981a oder https://deviq.com/design-patterns/guard-clause
+compare-char-value = Hier wird '{$expression}' vom Typ 'char' mit dem Wert '{$intValue}' verglichen. Es ist nicht offensichtlich für welchen Buchstabe der Wert steht, schreibe stattdessen '{$charValue}'.
 
 import-types = Statt den Pfad zum Typ anzugeben, sollte '{$type}' importiert werden. Datentypen aus dem selben Paket oder 'java.lang' müssen nicht explizit importiert werden.
 
@@ -186,7 +177,7 @@ binary-operator-on-boolean = Statt '|' und '&' sollte man '||' und '&&' verwende
 
 object-datatype = Statt dem Datentyp 'Object', sollte die Variable '{$variable}' einen konkreten oder generischen Datentyp haben.
 
-magic-string = Der String '{$value}' sollte in eine Konstante ausgelagert werden. Siehe Wiki Artikel zu Magic Strings.
+magic-string = Der String '{$value}' sollte in eine Konstante ausgelagert werden.
 
 loop-should-be-do-while = Diese Schleife sollte eine do-while Schleife sein, weil der Code vor der Schleife, der gleiche wie in der Schleife ist: {$suggestion}
 
@@ -196,7 +187,7 @@ loop-should-be-while = Diese Schleife sollte eine while Schleife sein: {$suggest
 # Naming
 bool-getter-name = Für boolean getter bietet es sich an ein Verb als Präfix zu verwenden. Zum Beispiel '{$newName}' statt '{$oldName}'.
 
-constants-name-exp = Der Name '{$name}' ist nicht aussagekräftig gegeben den Wert '{$value}'
+constants-name-exp = Der Name '{$name}' ist nicht aussagekräftig gegeben dem Wert '{$value}'
 constants-name-exp-value = Der Wert '{$value}' der Konstante '{$name}' sollte nicht im Namen vorkommen
 
 linguistic-naming-boolean = Der Name von '{$name}' deutet an, dass es vom Typ boolean ist oder diesen zurückgibt, stattdessen ist der Typ '{$type}'.
@@ -207,16 +198,16 @@ linguistic-naming-setter = Der Name von '{$name}' deutet an, dass es ein setter
 variable-name-single-letter = Der Bezeichner '{$name}' ist nicht aussagekräftig
 variable-is-abbreviation = Unnötige Abkürzung '{$name}'
 variable-name-type-in-name = Der Bezeichner '{$name}' sollte nicht den Typ im Namen haben
-similar-identifier = Der Bezeichner '{$left}' ist sehr ähnlich zu '{$right}'. Das kann zu Verwechslungen und Tippfehlern führen, weswegen man diesen umbenennen sollte.
+similar-identifier = Der Bezeichner '{$left}' ist sehr ähnlich zu '{$right}'.
 
 type-has-descriptive-name-pre-suffix = Der Name enthält unnötige Präfixe oder Suffixe
-type-has-descriptive-name-exception = Eine Klasse die von Exception erbt, sollte 'Exception' am Ende ihres Namens haben
+type-has-descriptive-name-exception = Eine Klasse die von 'Exception' erbt, sollte 'Exception' am Ende ihres Namens haben
 
 package-naming-convention = Der Name eines Pakets sollte am besten ein Wort sein und alle Buchstaben sollten nach Konvention
                             klein sein. Außer dem Zeichen '_' sollten zudem keine Sonderzeichen auftreten. An folgenden Stellen wird das
                             nicht eingehalten: '{$positions}'
 
-variable-redundant-number-suffix = Der Bezeichner '{$name}' enthält eine redundante Zahl am Ende.
+variable-redundant-number-suffix = Der Bezeichner '{$name}' enthält eine unnötige Zahl am Ende.
 
 # OOP
 concrete-collection = Der Typ '{$type}' sollte durch eine Schnittstelle wie zum Beispiel 'List' oder 'Set' ersetzt werden.
@@ -225,7 +216,7 @@ leaked-collection-return = Die Methode '{$method}' gibt eine Referenz zu dem Fel
 leaked-collection-constructor = Der Konstruktor '{$signature}' weißt dem Feld '{$field}' eine Referenz zu, dadurch ist es möglich das Feld von außerhalb zu verändern. Weise stattdessen eine Kopie dem Feld zu.
 leaked-collection-assign = Die Methode '{$method}' weißt dem Feld '{$field}' eine Referenz zu, dadurch ist es möglich das Feld von außerhalb zu verändern. Weise stattdessen eine Kopie dem Feld zu.
 
-method-should-be-abstract = {$type}::{$method} sollte abstrakt sein, anstatt eine Platzhalter-Implementierung anzugeben
+method-should-be-abstract = '{$type}::{$method}' sollte abstrakt sein, anstatt eine Platzhalter-Implementierung anzugeben.
 
 method-should-be-static = Die Methode '{$name}' sollte statisch sein, da sie auf keine Instanzattribute oder Methoden zugreift.
 
@@ -234,38 +225,48 @@ utility-exp-constructor = Utility-Klassen müssen genau einen privaten und param
 
 static-field-should-be-instance = Das statische Attribut '{$name}' sollte ein Instanzattribut sein.
 
-constants-class-exp = Konstanten sollten in der Klasse gespeichert werden in der sie auch verwendet werden und nicht in einer separaten Klasse. Siehe https://stackoverflow.com/a/15056462/7766117
+constants-class-exp = Konstanten sollten in der Klasse gespeichert werden in der sie auch verwendet werden und
+                      nicht in einer separaten Klasse.
 
 empty-interface-exp = Interfaces sollten nicht leer sein.
 
 ui-input-separation = Eingaben sollten nicht im Programm verteilt sein. Wurde auch verwendet in {$first}.
 ui-output-separation = Ausgaben sollten nicht im Programm verteilt sein. Wurde auch verwendet in {$first}.
 
-do-not-use-system-exit = System.exit() darf nicht verwendet werden. Strukturiere deinen Code so, dass er sich natürlich beendet.
+do-not-use-system-exit = 'System.exit()' darf nicht verwendet werden. Strukturiere deinen Code so, dass er sich natürlich beendet.
 
 avoid-inner-classes = Jede Klasse sollte in einer eigenen Datei sein. Innere-Klassen sollten vermieden werden.
 
-mutable-enum = Enums sollten nicht veränderbar sein. Siehe https://stackoverflow.com/a/41199773/7766117
+mutable-enum = Enums sollten nicht veränderbar sein.
 
 should-be-enum-attribute = Die Werte vom switch sollten Attribute des enums sein. Alternativ sollte man eine Map verwenden.
 
-closed-set-of-values-switch = Der Switch hat nur endlich viele cases. Dabei handelt es sich um eine abgeschlossene Menge, die als enum modelliert werden sollte. Die Werte sind: '{$values}'.
-closed-set-of-values-list = Die Auflistung hat nur endlich viele Werte und sollte deswegen als enum modelliert werden. Die Werte sind: '{$values}'.
-closed-set-of-values-method = Die Methode gibt nur die Konstanten Werte '{$values}' zurück. Dabei handelt es sich um endlich viele, weswegen man das als enum modellieren sollte.
+closed-set-of-values-switch = Der Switch hat nur endlich viele cases. Dabei handelt es sich um eine abgeschlossene Menge,
+                              die als enum modelliert werden sollte. Die Werte sind: '{$values}'.
+closed-set-of-values-list = Die Auflistung hat nur endlich viele Werte und sollte deswegen als enum modelliert werden.
+                            Die Werte sind: '{$values}'.
+closed-set-of-values-method = Die Methode gibt nur die Konstanten Werte '{$values}' zurück. Dabei handelt es sich um
+                              endlich viele, weswegen man das als enum modellieren sollte.
 
-do-not-use-instanceof = instanceof sollte nicht verwendet werden. Siehe Ilias Wiki.
-do-not-use-instanceof-emulation = instanceof sollte nicht verwendet werden und auch nicht durch getClass oder ClassCastException emuliert werden. Siehe Ilias Wiki.
+do-not-use-instanceof = 'instanceof' sollte nicht verwendet werden.
+do-not-use-instanceof-emulation = 'instanceof' sollte nicht verwendet werden und auch nicht durch 'getClass' oder
+                                  'ClassCastException' emuliert werden.
 
 abstract-class-without-abstract-method = Abstrakte Klassen sollten mindestens eine abstrakte Methode haben.
-composition-over-inheritance = Die Oberklasse hat nur Felder. Statt Vererbung sollte hier Komposition verwendet werden. Zum Beispiel ein interface mit dem getter: '{$suggestion}'.
-should-be-interface = Die Klasse hat nur Methoden und keine Felder. Statt Vererbung sollte hier ein Interface mit Standard-Implementierungen verwendet werden.
+composition-over-inheritance = Die Oberklasse hat nur Felder. Statt Vererbung sollte hier Komposition verwendet werden.
+                               Zum Beispiel ein interface mit dem getter: '{$suggestion}'.
+should-be-interface = Die Klasse hat nur Methoden und keine Felder. Statt Vererbung sollte hier ein Interface mit
+                      Standard-Implementierungen verwendet werden.
 
-avoid-static-blocks = Statische Blöcke sollten vermieden werden, da sie keine objekt-orientierte Lösung darstellen und schlecht erweiterbar sind. Statische Blöcke sollten durch eine objektorientierte Lösung ersetzt werden (bspw. Konstruktoren).
+avoid-static-blocks = Statische Blöcke sollten vermieden werden, da sie keine objekt-orientierte Lösung darstellen und
+                      schlecht erweiterbar sind. Statische Blöcke sollten durch eine objektorientierte Lösung ersetzt
+                      werden (bspw. Konstruktoren).
 
 # Structure
 
 default-package = Das default-Paket sollte nicht verwendet werden. Die folgenden Klassen sind im default-Paket: {$positions}
-too-few-packages = Das Projekt hat mehr als {$max} Klassen, aber nur ein Paket. Du solltest dir eine sinnvolle Einteilung der Klassen in mehrere Pakete überlegen (bspw. nach den Kriterien commands, logic, ui, ...).
+too-few-packages = Das Projekt hat mehr als {$max} Klassen, aber nur ein Paket. Verwende mehrere Pakete um die
+                   Klassen sinvoll zu gruppieren.
 
 # Unnecessary
 
diff --git a/autograder-core/src/main/resources/strings.en.ftl b/autograder-core/src/main/resources/strings.en.ftl
index 4e334258..f40c6b73 100644
--- a/autograder-core/src/main/resources/strings.en.ftl
+++ b/autograder-core/src/main/resources/strings.en.ftl
@@ -31,7 +31,7 @@ equals-hashcode-comparable-contract = Equals and hashCode must always be overrid
 use-enum-collection = For maps where an enum is used as a key and for sets as a value, one should use EnumMap/EnumSet.
 
 compare-to-zero = The result of #compareTo or #compare should only be compared to 0.
-                It is an implementation detail whether a given type returns strictly the values
+                It is an implementation detail whether a given type returns the values
                 '-1, 0, +1' or others.
 equals-using-hashcode = Implementing equals by just comparing hashCodes is fragile.
                 Hashes collide frequently, and this will lead to false positives in equals.
@@ -64,7 +64,7 @@ javadoc-method-exp-param-unknown = The JavaDoc comment mentions the parameter '{
 
 javadoc-unexpected-tag = The JavaDoc comment should not have an '@{$tag}' tag.
 
-javadoc-type-exp-invalid-author = The @author tag should contain your u-shorthand: {$authors}
+javadoc-type-exp-invalid-author = The @author tag should contain a u-shorthand: {$authors}
 
 javadoc-stub-exp-desc = Javadoc has an empty description
 javadoc-stub-exp-param = Stub description for parameter {$param}
@@ -76,9 +76,9 @@ javadoc-undocumented-throws = The exception {$exp} is thrown, but not mentioned
 todo-comment = TODOs should not be in the final submission.
 
 # Complexity
-use-diamond-operator = You can remove the types specified in the '< A, B, ... >' and just use '<>' instead, see https://docs.oracle.com/javase/tutorial/java/generics/genTypeInference.html and https://stackoverflow.com/a/16352848/7766117
+use-diamond-operator = The types specified in the '< A, B, ... >' can be remove, use '<>' instead.
 
-extends-object = Explicitly extending Object is unnecessary
+extends-object = Explicitly extending 'Object' is unnecessary
 
 for-loop-var = Each for-loop should have exactly one control variable
 
@@ -88,7 +88,7 @@ redundant-modifier = The following modifiers are redundant and should be removed
 
 redundant-return-exp = Unnecessary return
 
-self-assignment-exp = Useless assignment of {$rhs} to {$lhs}
+self-assignment-exp = Useless assignment of '{$rhs}' to '{$lhs}'
 
 too-many-exceptions = The project defines {$count} exceptions. Those are too many.
 
@@ -96,35 +96,33 @@ redundant-variable = The variable '{$name}' is redundant, the value can be used
 
 unused-import = The import '{$import}' is unused and should therefore be removed.
 
-redundant-boolean-equal = It is redundant to explicitly check if a condition equals true or false. Write instead '{$suggestion}'.
-
-use-operator-assignment-exp = Assignment can be simplified to '{$simplified}'
-
 complex-regex = Nontrivial regex need an explanation (score is {$score}, max allowed score is {$max})
 
 redundant-catch = An exception should not be caught and then rethrown immediately.
 
-redundant-uninitialized-variable = The variable '{$variable}' has been declared, but the value '{$value}' is not directly assigned. Instead you should write '{$suggestion}'.
+redundant-uninitialized-variable = The variable '{$variable}' has been declared, but the value '{$value}' is not directly assigned. Instead write '{$suggestion}'.
 
 merge-nested-if = The nested if can be combined with the outer if. The condition for the outer if should then be '{$suggestion}'.
 
-multiple-inline-statements = There should not be multiple statements in a single line. So no declarations of multiple variables or assignments in the same line.
+multiple-inline-statements = There should not be multiple statements in a single line.
 
-multi-threading = Multithreading is out of scope for this lecture. The code is only executed on a single thread. Writing it thread-safe makes the code unnecessarily complex.
+multi-threading = Multithreading is not used. The code is only executed on a single thread.
+                  Writing it thread-safe makes the code unnecessarily complex.
 
-try-catch-complexity = The complexity of try-catch-blocks should be kept low. There should be less than {$max} statements in the try-block. You should refactor the code into multiple methods or extract unnecessary statements out of the try-block.
+try-catch-complexity = The complexity of try-catch-blocks should be kept low.
+                       There should be less than {$max} statements in the try-block.
+                       Refactor the code into multiple methods or extract unnecessary
+                       statements out of the try-block.
 
 redundant-else = The 'else' is redundant. Write '{$expected}' instead of '{$given}'.
 
-redundant-assignment = The variable '{$variable}' is assigned a value that is never read, therefore the assignment can be removed.
+redundant-assignment = The variable '{$variable}' is assigned a value that is never read,
+                       therefore the assignment can be removed.
 
 # Debug
-assert-used-exp = Assertions crash the entire program if they evaluate to false.
-              Also they can be disabled, so never rely on them to e.g. check user input.
-              They are great for testing purposes, but should not be part of your final solution.
-              If you want to document an invariant, consider a comment.
+assert-used = Assertions should not be present in the final submission. Use exceptions instead.
 
-print-stack-trace = Don't print stack traces in your final solution
+print-stack-trace = Stack traces should not be printed in the final submission.
 
 # Exceptions
 custom-exception-inheritance-error = The custom exception '{$name}' should not extend 'Error'.
@@ -132,18 +130,18 @@ custom-exception-inheritance-runtime = The custom exception '{$name}' should ext
 
 empty-catch-block = Empty catch block
 
-exception-controlflow-caught = {$exception} thrown and immediately caught in a surrounding block
-exception-controlflow-should-not-be-caught = {$exception} should never be caught
+exception-controlflow-caught = '{$exception}' thrown and immediately caught in a surrounding block
+exception-controlflow-should-not-be-caught = '{$exception}' should never be caught
 
-runtime-exception-caught = RuntimeExceptions '{$exception}' should not be caught
+runtime-exception-caught = RuntimeException '{$exception}' should not be caught
 
 exception-message = An exception should always have a message that explains what the problem is and ideally how it occurred.
 
-number-format-exception-ignored = NumberFormatException should be caught or replaced through your own exception.
+number-format-exception-ignored = 'NumberFormatException' should be caught and/or replaced by self-defined exception.
 
 # General
 
-compare-objects-exp = Implement an equals method for type {$type} and use it for comparisons
+compare-objects-exp = Implement an equals method for type '{$type}' and use it for comparisons
 
 variable-should-be = The variable '{$variable}' should be '{$suggestion}'.
 
@@ -151,29 +149,25 @@ reassigned-parameter = The parameter '{$name}' should not be assigned a new valu
 
 double-brace-init = Don't use the obscure 'double brace initialization' syntax
 
-missing-override = '{$name}' should have an '@Override'-annotation, see https://stackoverflow.com/a/94411/7766117.
+missing-override = '{$name}' should have an '@Override'-annotation.
 
-system-specific-linebreak = Always use system-independent line breaks such as the value obtained from System.lineSeparator() or %n in format strings
+system-specific-linebreak = Always use system-independent line breaks such as the value obtained from 'System.lineSeparator()' or '%n' in format strings
 
 field-should-be-final = The attribute '{$name}' should be final.
 
-string-cmp-exp = Use the equals method: '{$lhs}.equals({$rhs})' instead of '{$lhs} == {$rhs}'
+do-not-use-raw-types-exp = Generic Types should always have generics and never be used as raw types.
 
-do-not-use-raw-types-exp = Generic Types should always have generics and never be used as raw types, see https://stackoverflow.com/a/2770692/7766117
+avoid-labels = Labels should be avoided.
 
-avoid-labels = Labels should be avoided. See https://stackoverflow.com/a/33689582/7766117.
+avoid-shadowing = The variable '{$name}' hides an attribute with the same name. Except for in the constructor/setters, this should be avoided.
 
-avoid-shadowing = The variable '{$name}' hides an attribute with the same name. Except for in the constructor, this should be avoided.
-
-suppress-warnings = @SuppressWarnings suppresses warnings from the compiler or Checkstyle, without fixing the underlying problem of the code.
+suppress-warnings = '@SuppressWarnings' suppresses warnings from the compiler or Checkstyle, without fixing the underlying problem of the code.
 
 scanner-closed = Scanner should be closed
 
 unchecked-type-cast = It has to be ensured that the type of the object is the same as that of the cast. Otherwise, the code might crash.
 
-compare-char-value = Here '{$expression}' of type char is compared with the value {$intValue}. It is not obvious which letter the value represents, therefore write '{$charValue}'.
-
-use-guard-clauses = The code cancels the normal control-flow through for example a return. if-else-blocks with those conditions can be written more beautifully using so called guard-clauses. This has the advantage that you can better recognize duplicate code. See for a detailed explanation https://medium.com/@scadge/if-statements-design-guard-clauses-might-be-all-you-need-67219a1a981a or https://deviq.com/design-patterns/guard-clause
+compare-char-value = Here '{$expression}' of type 'char' is compared with the value {$intValue}. It is not obvious which letter the value represents, therefore write '{$charValue}'.
 
 import-types = Instead of qualifying the type, '{$type}' should be imported. Types from the same package or 'java.lang' do not have to be imported explicitly.
 
@@ -186,7 +180,7 @@ binary-operator-on-boolean = Instead of '|' and '&' one should use '||' and '&&'
 
 object-datatype = Instead of the datatype 'Object', the variable '{$variable}' should have a concrete or generic datatype.
 
-magic-string = The string '{$value}' should be in a constant. See the wiki article for magic strings.
+magic-string = The string '{$value}' should be in a constant.
 
 loop-should-be-do-while = This loop should be a do-while loop, because the code before the loop is the same as the code in the loop: {$suggestion}
 
@@ -220,11 +214,17 @@ variable-redundant-number-suffix = The identifier '{$name}' has a redundant numb
 # OOP
 concrete-collection = The type '{$type}' should be replaced by an interface like 'List' or 'Set'.
 
-leaked-collection-return = The method '{$method}' returns a reference to the field '{$field}'. This allows the field to be modified from the outside. Instead, a copy should be returned.
-leaked-collection-constructor = The constructor '{$signature}' assigns a reference to the field '{$field}'. This allows the field to be modified from the outside. Instead, a copy should be made before setting the field.
-leaked-collection-assign = The method '{$method}' assigns a reference to the field '{$field}'. This allows the field to be modified from the outside. Instead, a copy should be made before setting the field.
+leaked-collection-return = The method '{$method}' returns a reference to the field '{$field}'.
+                           This allows the field to be modified from the outside.
+                           Instead, a copy should be returned.
+leaked-collection-constructor = The constructor '{$signature}' assigns a reference to the field '{$field}'.
+                                This allows the field to be modified from the outside. Instead,
+                                a copy should be made before setting the field.
+leaked-collection-assign = The method '{$method}' assigns a reference to the field '{$field}'.
+                           This enables modification of the field from the outside. Instead,
+                           a copy should be made before setting the field.
 
-method-should-be-abstract = {$type}::{$method} should be abstract and not provide a default implementation
+method-should-be-abstract = '{$type}::{$method}' should be abstract and not provide a default implementation
 
 method-should-be-static = The method '{$name}' should be static, because it does not access instance attributes or methods.
 
@@ -233,18 +233,18 @@ utility-exp-constructor = Utility classes must have a single private no-arg cons
 
 static-field-should-be-instance = The static field '{$name}' must not be static.
 
-constants-class-exp = Constants should be saved in the class they are used in and not in a separate class. See https://stackoverflow.com/a/15056462/7766117
+constants-class-exp = Constants should be saved in the class they are used in and not in a dedicated class.
 
 empty-interface-exp = Interfaces should not be empty.
 
 ui-input-separation = Input should not be spread over the program. Other use in {$first}.
 ui-output-separation = Output should not be spread over the program. Other use in {$first}.
 
-do-not-use-system-exit = System.exit() must not be used. Structure your code in so that it exits naturally.
+do-not-use-system-exit = 'System.exit()' must not be used. Structure code so that it exits naturally.
 
 avoid-inner-classes = Every class should be in its own file. Inner-Classes should be avoided.
 
-mutable-enum = Enums should be immutable. See https://stackoverflow.com/a/41199773/7766117
+mutable-enum = Enums should be immutable.
 
 should-be-enum-attribute = The values of the switch should be associated attributes of the enum. Alternatively, one should use a Map.
 
@@ -252,19 +252,27 @@ closed-set-of-values-switch = The switch has only finitely many cases. This is a
 closed-set-of-values-list = The listing only has finitely many values and should therefore be modeled as an enum. The values are: '{$values}'.
 closed-set-of-values-method = The method only returns the constant values '{$values}'. There are only finitely many, which is why one should model it as an enum.
 
-do-not-use-instanceof = instanceof should not be used. See Ilias Wiki.
-do-not-use-instanceof-emulation = instanceof should not be used and also not be emulated through getClass or ClassCastException. See Ilias Wiki.
+do-not-use-instanceof = 'instanceof' should not be used.
+do-not-use-instanceof-emulation = 'instanceof' should not be used and not be emulated through
+                                  'getClass' or 'ClassCastException'.
 
 abstract-class-without-abstract-method = Abstract classes should have at least one abstract method.
-composition-over-inheritance = The parent class has only fields. Instead of inheritance, composition should be used. For example through an interface with the getter: '{$suggestion}'.
-should-be-interface = The parent class has only methods without fields. Instead of inheritance an interface with default-implementations should be used.
+composition-over-inheritance = The parent class has only fields. Instead of inheritance, composition
+                               should be used. For example through an interface with the getter:
+                               '{$suggestion}'.
+should-be-interface = The parent class has only methods without fields. Instead of inheritance an
+                      interface with default-implementations should be used.
 
-avoid-static-blocks = Static blocks should be avoided because they are not expandable and object-oriented. Static blocks should be replaced by an object-oriented solution (e.g. constructor).
+avoid-static-blocks = Static blocks should be avoided because they are not expandable and
+                      object-oriented. Static blocks should be replaced by an object-oriented
+                      solution (e.g. constructor).
 
 # Structure
 
-default-package = The default-package should not be used. The following classes are in the default-package: {$positions}
-too-few-packages = The project has more than {$max} classes, but only one package is used. You should think about a better classification for the different classes to distribute the classes over multiple packages (e.g. commands, logic, ui, ...).
+default-package = The default-package should not be used. The following classes are in the
+                  default-package: {$positions}
+too-few-packages = The project has more than {$max} classes, but only one package is used.
+                   Use multiple packages to structure the code.
 
 # Unnecessary
 empty-block = Empty blocks should be removed or have a comment explaining why they are empty.
diff --git a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/UseGuardClauses/code/Test.java b/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/UseGuardClauses/code/Test.java
deleted file mode 100644
index 6ee7f565..00000000
--- a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/UseGuardClauses/code/Test.java
+++ /dev/null
@@ -1,89 +0,0 @@
-package de.firemage.autograder.core.check_tests.UseGuardClauses.code;
-
-public class Test {
-    public static void main(String[] args) {
-    }
-
-    void run(Timer timer) {
-        if (!timer.isEnabled())
-            return;
-
-        if (!timer.isValid())
-            throw new IllegalArgumentException();
-
-        timer.run();
-    }
-
-    void run2(Timer timer) {
-        if (timer.isEnabled() && timer.isValid()) {
-            timer.run();
-        } else if (!timer.isEnabled()) { /*# not ok #*/
-            return;
-        } else if (!timer.isValid()) { /*# not ok #*/
-            throw new IllegalArgumentException();
-        }
-    }
-
-    void example(boolean a) {
-        if (a) { /*# ok #*/
-            System.out.println("a");
-            return; // early return
-        } else {
-            System.out.println("b");
-            // normal code path
-        }
-    }
-
-    void isOkay(boolean a, boolean b) {
-        if (a) {
-            // do something
-        } else if (b) {
-            // do some other thing
-        } else {
-            // do some third thing
-        }
-
-        // something that is always done
-    }
-
-    void withLoop(boolean a, boolean b) {
-        while (a) {
-            if (b) {
-                System.out.println("hello");
-            } else { /*# not ok #*/
-                continue;
-            }
-        }
-    }
-
-    void bigExample(boolean a, boolean b, boolean c, boolean d) {
-        if (a) {
-            if (b) {
-                if (c) {
-                    // do something
-                } else if (d) {
-                    // do something
-                } else { /*# not ok #*/
-                    throw new IllegalArgumentException();
-                }
-            } else { /*# not ok #*/
-                throw new IllegalArgumentException();
-            }
-        } else { /*# not ok #*/
-            throw new IllegalArgumentException();
-        }
-    }
-}
-
-class Timer {
-    boolean isEnabled() {
-        return true;
-    }
-
-    boolean isValid() {
-        return true;
-    }
-
-    void run() {
-    }
-}
diff --git a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/UseGuardClauses/config.txt b/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/UseGuardClauses/config.txt
deleted file mode 100644
index 90f75e7b..00000000
--- a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/UseGuardClauses/config.txt
+++ /dev/null
@@ -1,8 +0,0 @@
-general.UseGuardClauses
-Use guard clauses to simplify code and make it more readable.
-Test.java:20-22
-Test.java:22-24
-Test.java:53-55
-Test.java:66-68
-Test.java:69-71
-Test.java:72-74

From 4c6170b092891d55e83f331ef040979412dfccbc Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Sun, 24 Nov 2024 12:18:15 +0100
Subject: [PATCH 02/12] revert #567 (update to java 21) and some minor
 adjustments

---
 .../core/check/api/SequentialAddAll.java      |  8 +++---
 .../check/comment/UnnecessaryComment.java     |  8 ++----
 .../core/check/oop/LeakedCollectionCheck.java | 18 ++++++-------
 .../autograder/core/check/utils/Option.java   |  8 +++---
 .../core/integrated/ExpressionUtil.java       |  3 ---
 .../autograder/core/integrated/TypeUtil.java  |  4 +++
 .../core/integrated/UsesFinder.java           | 25 ++++++++++---------
 .../structure/StructuralElement.java          |  4 +--
 .../structure/StructuralEqualsVisitor.java    |  5 ++--
 pom.xml                                       |  2 +-
 10 files changed, 42 insertions(+), 43 deletions(-)

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/api/SequentialAddAll.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/api/SequentialAddAll.java
index d7db6796..0a92d558 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/api/SequentialAddAll.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/api/SequentialAddAll.java
@@ -62,7 +62,7 @@ static Optional<AddInvocation> of(CtStatement ctStatement) {
                 return Optional.empty();
             }
 
-            return Optional.of(new AddInvocation(collection, executableReference, ctInvocation.getArguments().get(0)));
+            return Optional.of(new AddInvocation(collection, executableReference, ctInvocation.getArguments().getFirst()));
         }
     }
 
@@ -91,7 +91,7 @@ private void reportProblem(CtVariableReference<?> ctVariable, List<? extends CtE
 
         if (ctEnum != null && UseEnumValues.checkEnumValues(ctEnum, TypeUtil.isOrderedCollection(ctVariable.getType()), fieldReads)) {
             addLocalProblem(
-                values.get(0).getParent(CtStatement.class),
+                values.getFirst().getParent(CtStatement.class),
                 new LocalizedMessage(
                     "common-reimplementation",
                     Map.of(
@@ -138,12 +138,12 @@ private void reportProblem(CtVariableReference<?> ctVariable, List<? extends CtE
         }
 
         addLocalProblem(
-            values.get(0).getParent(CtStatement.class),
+            values.getFirst().getParent(CtStatement.class),
             new LocalizedMessage(
                 "common-reimplementation",
                 Map.of(
                     "suggestion", "private static final List<%s> SOME_GOOD_NAME = List.of(%s); /* ... */ %s.addAll(SOME_GOOD_NAME)".formatted(
-                        ExpressionUtil.getExpressionType(values.get(0)),
+                        ExpressionUtil.getExpressionType(values.getFirst()),
                         values.stream()
                             .map(CtElement::toString)
                             .collect(Collectors.joining(", ")),
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java
index 27e74d7c..7be14144 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java
@@ -42,11 +42,7 @@ private void checkComments(Collection<? extends CtComment> comments) {
     }
 
     private static boolean isStandaloneComment(CtComment ctComment) {
-        var parent = ctComment.getParent();
-        if (parent == null) {
-            return false;
-        }
-        return !parent.getComments().contains(ctComment);
+        return ctComment.getParent() instanceof CtElement ctElement && !ctElement.getComments().contains(ctComment);
     }
 
     @Override
@@ -75,7 +71,7 @@ public void process(CtElement element) {
                         .map(CtComment.class::cast)
                         .collect(Collectors.toCollection(ArrayList::new));
 
-                    followingComments.add(0, ctComment);
+                    followingComments.addFirst(ctComment);
 
                     checkComments(followingComments);
                     return;
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
index c23265df..8f748cda 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
@@ -241,9 +241,7 @@ private static List<CtExpression<?>> findPreviousAssignee(CtVariableRead<?> ctVa
 
         boolean foundPreviousAssignment = false;
         CtStatement currentStatement = ctVariableRead.getParent(CtStatement.class);
-        var reversedStatements = new ArrayList<>(StatementUtil.getEffectiveStatements(ctExecutable.getBody()));
-        Collections.reverse(reversedStatements);
-        for (CtStatement ctStatement : reversedStatements) {
+        for (CtStatement ctStatement : StatementUtil.getEffectiveStatements(ctExecutable.getBody()).reversed()) {
             if (!foundPreviousAssignment) {
                 if (ctStatement == currentStatement) {
                     foundPreviousAssignment = true;
@@ -282,7 +280,7 @@ && isParameterOf(ctVariableDeclaration, ctExecutable)) {
             List<CtExpression<?>> previousAssignees = findPreviousAssignee(ctVariableRead);
 
             if (!previousAssignees.isEmpty()) {
-                return findParameterReference(previousAssignees.get(0), ctExecutable);
+                return findParameterReference(previousAssignees.getFirst(), ctExecutable);
             }
 
             return Option.some((CtParameter<?>) ctVariableDeclaration);
@@ -445,11 +443,13 @@ private <T> void checkCtType(CtType<T> ctType) {
                         ctTypeMember = fixRecordAccessor(ctRecord, ctMethod);
                     }
 
-                    if (ctTypeMember instanceof CtConstructor<?> ctConstructor) {
-                        checkCtExecutableAssign(ctConstructor);
-                    } else if (ctTypeMember instanceof CtMethod<?> ctMethod) {
-                        checkCtExecutableReturn(ctMethod);
-                        checkCtExecutableAssign(ctMethod);
+                    switch (ctTypeMember) {
+                        case CtConstructor<?> ctConstructor -> checkCtExecutableAssign(ctConstructor);
+                        case CtMethod<?> ctMethod -> {
+                            checkCtExecutableReturn(ctMethod);
+                            checkCtExecutableAssign(ctMethod);
+                        }
+                        default -> {}
                     }
                 }
             }
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java
index ba0598cf..edb044bc 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java
@@ -33,8 +33,8 @@ default boolean isSome() {
     }
 
     default <U> Option<U> map(Function<T, U> function) {
-	    if (this instanceof Some<T> someValue) {
-            return new Some<>(function.apply(someValue.value));
+        if (this instanceof Some<T>(T value)) {
+            return new Some<>(function.apply(value));
         } else if (this instanceof None<T>) {
             return new None<>();
         }
@@ -56,8 +56,8 @@ default T nullable() {
     }
 
     default Stream<T> stream() {
-        if (this instanceof Some<T> someValue) {
-            return Stream.of(someValue.value);
+        if (this instanceof Some<T>(T value)) {
+            return Stream.of(value);
         } else if (this instanceof None<T>) {
             return Stream.empty();
         }
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/ExpressionUtil.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/ExpressionUtil.java
index ef3784ee..bda24efa 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/ExpressionUtil.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/ExpressionUtil.java
@@ -10,7 +10,6 @@
 import spoon.reflect.code.CtBinaryOperator;
 import spoon.reflect.code.CtConditional;
 import spoon.reflect.code.CtExpression;
-import spoon.reflect.code.CtFieldRead;
 import spoon.reflect.code.CtInvocation;
 import spoon.reflect.code.CtLiteral;
 import spoon.reflect.code.CtTextBlock;
@@ -20,8 +19,6 @@
 import spoon.reflect.code.LiteralBase;
 import spoon.reflect.code.UnaryOperatorKind;
 import spoon.reflect.declaration.CtElement;
-import spoon.reflect.declaration.CtEnum;
-import spoon.reflect.declaration.CtEnumValue;
 import spoon.reflect.declaration.CtTypedElement;
 import spoon.reflect.declaration.CtVariable;
 import spoon.reflect.eval.PartialEvaluator;
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/TypeUtil.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/TypeUtil.java
index 56557f0d..3129d3ad 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/TypeUtil.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/TypeUtil.java
@@ -137,6 +137,10 @@ public static boolean isTypeEqualTo(CtTypeReference<?> ctType, CtTypeReference<?
     public static boolean isSubtypeOf(CtTypeReference<?> ctTypeReference, Class<?> expected) {
         CtType<?> expectedType = ctTypeReference.getFactory().Type().get(expected);
 
+        return isSubtypeOf(ctTypeReference, expectedType);
+    }
+
+    public static boolean isSubtypeOf(CtTypeReference<?> ctTypeReference, CtType<?> expectedType) {
         if (ctTypeReference.getTypeDeclaration() == null || ctTypeReference instanceof CtTypeParameterReference) {
             return ctTypeReference.isSubtypeOf(expectedType.getReference());
         }
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java
index 3be22dbb..32a83697 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java
@@ -38,6 +38,7 @@
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.SequencedSet;
 import java.util.Set;
 import java.util.stream.Stream;
 
@@ -78,16 +79,13 @@ private static UsesFinder getFor(FactoryAccessor factoryAccessor) {
      */
     @SuppressWarnings("rawtypes")
     public static CtElementStream<CtElement> getAllUses(CtNamedElement element) {
-        if (element instanceof CtVariable variable) {
-            return UsesFinder.variableUses(variable).asUntypedStream();
-        } else if (element instanceof CtTypeParameter typeParameter) {
-            return UsesFinder.typeParameterUses(typeParameter).asUntypedStream();
-        } else if (element instanceof CtExecutable executable) {
-            return UsesFinder.executableUses(executable).asUntypedStream();
-        } else if (element instanceof CtType type) {
-            return UsesFinder.typeUses(type).asUntypedStream();
-        }
-        throw new IllegalArgumentException("Unsupported element: " + element.getClass().getName());
+        return switch (element) {
+            case CtVariable variable -> UsesFinder.variableUses(variable).asUntypedStream();
+            case CtTypeParameter typeParameter -> UsesFinder.typeParameterUses(typeParameter).asUntypedStream();
+            case CtExecutable executable -> UsesFinder.executableUses(executable).asUntypedStream();
+            case CtType type -> UsesFinder.typeUses(type).asUntypedStream();
+            default -> throw new IllegalArgumentException("Unsupported element: " + element.getClass().getName());
+        };
     }
 
     public static CtElementStream<CtVariableAccess<?>> variableUses(CtVariable<?> variable) {
@@ -183,7 +181,10 @@ public static boolean isAccessingVariable(CtVariable<?> ctVariable, CtVariableAc
     }
 
     public static CtVariable<?> getDeclaredVariable(CtVariableAccess<?> ctVariableAccess) {
-        return UsesFinder.getFor(ctVariableAccess).scanner.variableAccessDeclarations.getOrDefault(ctVariableAccess, null);
+        return UsesFinder.getFor(ctVariableAccess).scanner.variableAccessDeclarations.getOrDefault(
+            ctVariableAccess,
+            VariableUtil.getVariableDeclaration(ctVariableAccess.getVariable())
+        );
     }
     /**
      * The scanner searches for uses of supported code elements in a single pass over the entire model.
@@ -198,7 +199,7 @@ private static class UsesScanner extends CtScanner {
         private final Map<CtTypeParameter, List<CtTypeParameterReference>> typeParameterUses = new IdentityHashMap<>();
         private final Map<CtExecutable, List<CtElement>> executableUses = new IdentityHashMap<>();
         private final Map<CtType, List<CtTypeReference>> typeUses = new IdentityHashMap<>();
-        private final Map<CtType, Set<CtType>> subtypes = new IdentityHashMap<>();
+        private final Map<CtType, SequencedSet<CtType>> subtypes = new IdentityHashMap<>();
 
         // Caches the current instanceof pattern variables, since Spoon doesn't track them yet
         // We are conservative: A pattern introduces a variable until the end of the current block
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java
index 3d066483..4d8dc244 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java
@@ -12,11 +12,11 @@ public boolean equals(Object otherObject) {
         if (this == otherObject) {
             return true;
         }
-        if (!(otherObject instanceof StructuralElement<?> otherStructuralElement)) {
+        if (!(otherObject instanceof StructuralElement<?>(var otherElement))) {
             return false;
         }
 
-        return StructuralEqualsVisitor.equals(this.element, otherStructuralElement.element);
+        return StructuralEqualsVisitor.equals(this.element, otherElement);
     }
 
     @Override
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java
index f57f65d3..9de6e57a 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java
@@ -15,6 +15,7 @@
 import spoon.support.visitor.equals.EqualsVisitor;
 
 import java.util.LinkedHashSet;
+import java.util.SequencedSet;
 import java.util.Set;
 
 public final class StructuralEqualsVisitor extends EqualsVisitor {
@@ -25,7 +26,7 @@ public final class StructuralEqualsVisitor extends EqualsVisitor {
         CtRole.COMMENT, CtRole.COMMENT_CONTENT, CtRole.COMMENT_TAG, CtRole.COMMENT_TYPE
     );
 
-    private final Set<Difference> differences;
+    private final SequencedSet<Difference> differences;
 
     public record Difference(CtRole role, Object left, Object right) {}
 
@@ -117,7 +118,7 @@ protected boolean fail(CtRole role, Object element, Object other) {
      *
      * @return the differences
      */
-    public Set<Difference> differences() {
+    public SequencedSet<Difference> differences() {
         return new LinkedHashSet<>(this.differences);
     }
 }
diff --git a/pom.xml b/pom.xml
index 72fa78be..b82893b4 100644
--- a/pom.xml
+++ b/pom.xml
@@ -38,7 +38,7 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 
-        <java.version>17</java.version>
+        <java.version>21</java.version>
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
         <maven.compiler.release>${java.version}</maven.compiler.release>

From 294210a34b3f015b17e91ac0f171c7d9180d2b63 Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 09:29:31 +0100
Subject: [PATCH 03/12] fix spelling mistake

---
 autograder-core/src/main/resources/strings.de.ftl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/autograder-core/src/main/resources/strings.de.ftl b/autograder-core/src/main/resources/strings.de.ftl
index 1727da12..94754cc6 100644
--- a/autograder-core/src/main/resources/strings.de.ftl
+++ b/autograder-core/src/main/resources/strings.de.ftl
@@ -213,8 +213,8 @@ variable-redundant-number-suffix = Der Bezeichner '{$name}' enthält eine unnöt
 concrete-collection = Der Typ '{$type}' sollte durch eine Schnittstelle wie zum Beispiel 'List' oder 'Set' ersetzt werden.
 
 leaked-collection-return = Die Methode '{$method}' gibt eine Referenz zu dem Feld '{$field}' zurück. Dadurch ist es möglich das Feld von außerhalb zu verändern. Gebe stattdessen eine Kopie zurück.
-leaked-collection-constructor = Der Konstruktor '{$signature}' weißt dem Feld '{$field}' eine Referenz zu, dadurch ist es möglich das Feld von außerhalb zu verändern. Weise stattdessen eine Kopie dem Feld zu.
-leaked-collection-assign = Die Methode '{$method}' weißt dem Feld '{$field}' eine Referenz zu, dadurch ist es möglich das Feld von außerhalb zu verändern. Weise stattdessen eine Kopie dem Feld zu.
+leaked-collection-constructor = Der Konstruktor '{$signature}' weist dem Feld '{$field}' eine Referenz zu, dadurch ist es möglich das Feld von außerhalb zu verändern. Weise stattdessen eine Kopie dem Feld zu.
+leaked-collection-assign = Die Methode '{$method}' weist dem Feld '{$field}' eine Referenz zu, dadurch ist es möglich das Feld von außerhalb zu verändern. Weise stattdessen eine Kopie dem Feld zu.
 
 method-should-be-abstract = '{$type}::{$method}' sollte abstrakt sein, anstatt eine Platzhalter-Implementierung anzugeben.
 

From 60ff2a011ed9f9f5ee088d4ba54c08d96c4a8e4e Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 09:52:08 +0100
Subject: [PATCH 04/12] fix chained if check, improve tests and improve
 suggestion #631 #649

---
 .../core/check/complexity/ChainedIfCheck.java |  49 ++-
 .../check/complexity/TestChainedIfCheck.java  | 372 ++++++++++++++++++
 .../check_tests/ChainedIfCheck/code/Test.java | 104 -----
 .../check_tests/ChainedIfCheck/config.txt     |   8 -
 4 files changed, 416 insertions(+), 117 deletions(-)
 create mode 100644 autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestChainedIfCheck.java
 delete mode 100644 autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/ChainedIfCheck/code/Test.java
 delete mode 100644 autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/ChainedIfCheck/config.txt

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/ChainedIfCheck.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/ChainedIfCheck.java
index 75fdb9b0..919a34dd 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/ChainedIfCheck.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/ChainedIfCheck.java
@@ -9,6 +9,7 @@
 import de.firemage.autograder.core.integrated.StaticAnalysis;
 import spoon.processing.AbstractProcessor;
 import spoon.reflect.code.CtBlock;
+import spoon.reflect.code.CtExpression;
 import spoon.reflect.code.CtIf;
 import spoon.reflect.code.CtStatement;
 
@@ -27,12 +28,48 @@ public void process(CtIf ctIf) {
                     return;
                 }
 
+                // We can combine a nested if with the parent if, when the code looks like this:
+                // if (a) {
+                //     if (b) {
+                //         ...
+                //     }
+                // }
+                //
+                // ...
+                //
+                // Because there is
+                // - no code before/after the if(b)
+                // - there is no explicit else branch
+                //
+                // If there is an else or else if, we cannot merge the if-statements:
+                // if (a) {
+                //     if (b) {
+                //         ...
+                //     }
+                // } else {
+                //     ...
+                // }
+                //
+                // Because the code would behave differently if the condition a is true and b is false.
+                //
+                // Technically, one could solve this by adjusting the else to have a condition:
+                // } else if (a && !b || !a) {
+                //
+                // but that is not obvious, which is why it is not suggested.
+
                 // check if the if-statement has a nested if:
                 List<CtStatement> thenStatements = StatementUtil.getEffectiveStatements(ctIf.getThenStatement());
-                if (thenStatements.size() == 1
+                if (// a nested if is exactly one statement
+                    thenStatements.size() == 1
+                    // the statement must be an if-statement
                     && thenStatements.get(0) instanceof CtIf nestedIf
+                    // and that nested if must not have an else branch
                     && (nestedIf.getElseStatement() == null
-                        || StatementUtil.getEffectiveStatements(nestedIf.getElseStatement()).isEmpty())) {
+                        // or if it has one, it should be effectively empty
+                        || StatementUtil.getEffectiveStatements(nestedIf.getElseStatement()).isEmpty())
+                    // and like described above, there must not be an else branch in the parent if
+                    && ctIf.getElseStatement() == null
+                ) {
                     addLocalProblem(
                         ctIf.getCondition(),
                         new LocalizedMessage(
@@ -49,6 +86,7 @@ public void process(CtIf ctIf) {
                     );
                 }
 
+                // Now check if the else branch has a nested if, which could be merged with the parent if:
                 CtStatement elseStatement = ctIf.getElseStatement();
                 if (!(elseStatement instanceof CtBlock<?> ctBlock) || ctBlock.getStatements().isEmpty()) {
                     return;
@@ -60,11 +98,12 @@ public void process(CtIf ctIf) {
                 }
 
                 if (statements.get(0) instanceof CtIf ctElseIf && !elseStatement.isImplicit()) {
+                    CtExpression<?> condition = ctElseIf.getCondition();
+
                     addLocalProblem(
                         ctElseIf.getCondition(),
-                        new LocalizedMessage("suggest-replacement", Map.of(
-                            "original", "else {\"{\"} if (...) {\"{\"} ... {\"}\"} {\"}\"}",
-                            "suggestion", "else if (...) {\"{\"} ... {\"}\"}"
+                        new LocalizedMessage("common-reimplementation", Map.of(
+                            "suggestion", "} else if (%s) { ... }".formatted(condition)
                         )),
                         ProblemType.UNMERGED_ELSE_IF
                     );
diff --git a/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestChainedIfCheck.java b/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestChainedIfCheck.java
new file mode 100644
index 00000000..a295b96b
--- /dev/null
+++ b/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestChainedIfCheck.java
@@ -0,0 +1,372 @@
+package de.firemage.autograder.core.check.complexity;
+
+import de.firemage.autograder.api.JavaVersion;
+import de.firemage.autograder.api.LinterException;
+import de.firemage.autograder.core.LocalizedMessage;
+import de.firemage.autograder.core.Problem;
+import de.firemage.autograder.core.ProblemType;
+import de.firemage.autograder.core.check.AbstractCheckTest;
+import de.firemage.autograder.core.file.StringSourceInfo;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class TestChainedIfCheck extends AbstractCheckTest {
+    private static final List<ProblemType> PROBLEM_TYPES = List.of(ProblemType.MERGE_NESTED_IF, ProblemType.UNMERGED_ELSE_IF);
+
+    private void assertEqualsNested(Problem problem, String suggestion) {
+        assertEquals(
+            this.linter.translateMessage(
+                new LocalizedMessage(
+                    "merge-nested-if",
+                    Map.of("suggestion", suggestion)
+                )),
+            this.linter.translateMessage(problem.getExplanation())
+        );
+    }
+
+    private void assertEqualsElseIf(Problem problem, String suggestion) {
+        assertEquals(
+            this.linter.translateMessage(
+                new LocalizedMessage("common-reimplementation", Map.of(
+                    "suggestion", "} else if (%s) { ... }".formatted(suggestion)
+                ))
+            ),
+            this.linter.translateMessage(problem.getExplanation())
+        );
+    }
+
+    @Test
+    void testNestedIfsWithImplicitElse() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void main(String[] args) {
+                        if (true) {
+                            if (false) {
+                            }
+                        }
+                    }
+                }
+                """
+        ), PROBLEM_TYPES);
+
+
+        assertEqualsNested(problems.next(), "true && false");
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testNestedIfsWithOuterElse() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void main(String[] args) {
+                        if (true) {
+                            if (false) {
+                                System.out.println("A");
+                            }
+                        } else {
+                            System.out.println("B");
+                        }
+                    }
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testElseIfWithNestedIfNoElse() throws LinterException, IOException {
+        // TODO: again think of when this will be a problem with control flow?
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x, int y) {
+                        if (x == 0) {
+                            System.out.println("A");
+                        } else if (x == 1) {
+                            if (y == 0) {
+                                System.out.println("B");
+                            }
+                        }
+                    }
+
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        assertEqualsNested(problems.next(), "x == 1 && y == 0");
+
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testElseIfWithNestedIfWithElse() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x, int y) {
+                        if (x == 0) {
+                            System.out.println("A");
+                        } else if (x == 1) {
+                            if (y == 0) {
+                                System.out.println("B");
+                            }
+                        } else {
+                            System.out.println("C");
+                        }
+                    }
+
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testRegularIfElseIfElseChain() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x, int y) {
+                        if (x == 0) {
+                            System.out.println("A");
+                        } else if (x == 1) {
+                            System.out.println("B");
+                        } else {
+                            System.out.println("C");
+                        }
+                    }
+
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testElseWithNestedIfAndCode() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x, int y) {
+                        if (x == 0) {
+                        } else if (x == 1) {
+                        } else {
+                            System.out.println("A");
+                            if (x == 2) {
+                                System.out.println("B");
+                            }
+                        }
+                    }
+
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testElseWithNestedIf() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x, int y) {
+                        if (x == 0) {
+                        } else if (x == 1) {
+                        } else {
+                            if (x == 2) {
+                                System.out.println("B");
+                            }
+                        }
+                    }
+
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        assertEqualsElseIf(problems.next(), "x == 2");
+
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testCombineNestedIf() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x) {
+                        if (x > 0) {
+                            if (x < 10) {
+                                System.out.println("A");
+                            }
+                        }
+                    }
+                
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        assertEqualsNested(problems.next(), "x > 0 && x < 10");
+
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testNestedIfWithReturn() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int a) {
+                        if (a <= 0) {
+                            if (a == -3) {
+                                System.out.println("a is -3");
+                            }
+                            return;
+                        }
+                    }
+                
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+
+
+    @Test
+    void testComplicatedIfWithNested() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int a, int b) {
+                        if (a == 1) {
+                            if (b == 2) {
+                                System.out.println("a is 1");
+                            }
+                        } else if (a == 2) {
+                            if (b == 3) {
+                                throw new IllegalStateException("an error occurred");
+                            }
+                            System.out.println("a is 2");
+                        } else if (a == 3) {
+                            if (b == 3) {
+                                System.out.println("a is 3 and b is 3");
+                            } else {
+                                throw new IllegalStateException("should never happen");
+                            }
+                        }
+                    }
+
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testCombineNestedIfWithCode() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x) {
+                        if (x > 0) {
+                            System.out.println("A");
+                            if (x < 10) {
+                                System.out.println("B");
+                            }
+                        }
+                    }
+                
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+
+    @Test
+    void testCombineNestedIfTrailingCode() throws LinterException, IOException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x) {
+                        if (x > 0) {
+                            if (x < 10) {
+                                System.out.println("B");
+                            }
+                            System.out.println("A");
+                        }
+                    }
+                
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+
+
+    @Test
+    void testIfWithoutBlock() throws LinterException, IOException {
+        // this resulted in a crash in the past
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public static void callable(int x) {
+                        if (x > 0);
+                    }
+                
+                    public static void main(String[] args) {}
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+}
diff --git a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/ChainedIfCheck/code/Test.java b/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/ChainedIfCheck/code/Test.java
deleted file mode 100644
index b067f80b..00000000
--- a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/ChainedIfCheck/code/Test.java
+++ /dev/null
@@ -1,104 +0,0 @@
-public class Test {
-    public static void main(String[] args) {
-        if (true) { /*# not ok #*/
-            if (false) {
-
-            }
-        }
-
-        if (true) { /*# not ok #*/
-            if (false) {
-
-            }
-        } else {
-
-        }
-
-        if (true) {
-
-        } else if (true) { /*# not ok #*/
-            if (false) {
-
-            }
-        }
-
-        if (true) {
-
-        } else if (true) {
-
-        } else {
-
-        }
-
-        if (true) {
-
-        } else if (true) {
-
-        } else {
-            foo(); /*# ok #*/
-        }
-
-        if (true) {
-
-        } else if (true) {
-
-        } else {
-            foo(); /*# ok #*/
-            if (true) {
-
-            }
-        }
-
-        if (true) {
-
-        } else if (true) {
-
-        } else {
-            if (true) { /*# not ok #*/
-            }
-        }
-
-        if (true) {
-
-        } else if (true) {
-
-        } else {
-            if (true) { /*# not ok #*/
-            } else {
-
-            }
-        }
-    }
-
-    private static void foo() {
-
-    }
-}
-
-// Tests from https://github.com/pmd/pmd/blob/e8dbb54cb5ed682d9dfd4f54895f4bbd73be728e/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/design/xml/CollapsibleIfStatements.xml#L4
-class PmdTests {
-    void callable(boolean x, boolean y) {
-        if (x) { /*# not ok #*/
-            if (y) {
-            }
-        }
-
-        if (x) { /*# ok #*/
-            int z = 5;
-            if (y) {
-            }
-        }
-
-        if (x) { /*# ok #*/
-            if (y) {
-            }
-            int z = 5;
-        }
-    }
-}
-
-class CrashChainedIf {
-    void isTrue(boolean a) {
-        if (a); /*# ok #*/
-    }
-}
diff --git a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/ChainedIfCheck/config.txt b/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/ChainedIfCheck/config.txt
deleted file mode 100644
index e79ff561..00000000
--- a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/ChainedIfCheck/config.txt
+++ /dev/null
@@ -1,8 +0,0 @@
-complexity.ChainedIfCheck
-Avoid else { if () { } }
-Test.java:3
-Test.java:9
-Test.java:19
-Test.java:57
-Test.java:66
-Test.java:81

From 8e608be094547d79a73e98e8edb71e7920aa8bdd Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 09:52:30 +0100
Subject: [PATCH 05/12] remove TODO

---
 .../autograder/core/check/complexity/TestChainedIfCheck.java     | 1 -
 1 file changed, 1 deletion(-)

diff --git a/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestChainedIfCheck.java b/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestChainedIfCheck.java
index a295b96b..2f6c9f6f 100644
--- a/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestChainedIfCheck.java
+++ b/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestChainedIfCheck.java
@@ -87,7 +87,6 @@ public static void main(String[] args) {
 
     @Test
     void testElseIfWithNestedIfNoElse() throws LinterException, IOException {
-        // TODO: again think of when this will be a problem with control flow?
         ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
             JavaVersion.JAVA_17,
             "Test",

From 796ec7147d34e783729e2b5c3a452d04a633e802 Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 11:31:03 +0100
Subject: [PATCH 06/12] Add test for spoon bug

---
 .../TestRedundantIfForBooleanCheck.java       | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestRedundantIfForBooleanCheck.java b/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestRedundantIfForBooleanCheck.java
index 792dadab..606c81cb 100644
--- a/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestRedundantIfForBooleanCheck.java
+++ b/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestRedundantIfForBooleanCheck.java
@@ -7,6 +7,7 @@
 import de.firemage.autograder.core.check.AbstractCheckTest;
 import de.firemage.autograder.api.JavaVersion;
 import de.firemage.autograder.core.file.StringSourceInfo;
+import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 
 import java.io.IOException;
@@ -378,4 +379,28 @@ public boolean doA(int a) {
 
         problems.assertExhausted();
     }
+
+    @Disabled("This is a bug in Spoon, should be fixed by the PR spoon#6094")
+    @Test
+    void testMissingParensAroundStringConcatSuggestion() throws IOException, LinterException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Test",
+            """
+                public class Test {
+                    public boolean isRotation(String word, String rotation) {
+                        if (word.length() != rotation.length()) {
+                            return false;
+                        }
+
+                        return (word + word).contains(rotation);
+                    }
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        assertEqualsRedundant(problems.next(), "return word.length() == rotation.length() && (word + word).contains(rotation)");
+
+        problems.assertExhausted();
+    }
 }

From 306549c92ca75f875c5645f97c05c838f2b3229e Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 11:34:36 +0100
Subject: [PATCH 07/12] fix #626

---
 .../core/check/naming/ConstantsHaveDescriptiveNamesCheck.java   | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/naming/ConstantsHaveDescriptiveNamesCheck.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/naming/ConstantsHaveDescriptiveNamesCheck.java
index 8d749d2c..9feafeee 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/naming/ConstantsHaveDescriptiveNamesCheck.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/naming/ConstantsHaveDescriptiveNamesCheck.java
@@ -114,6 +114,8 @@ private static List<String> listCharOptions(char c) {
             case '_' -> List.of("underscore", "dash", "line");
             case '/', '\\' -> List.of("slash", "backslash");
             case '[', ']' -> List.of("bracket");
+            case '*' -> List.of("star", "asterisk");
+            case '+' -> List.of("plus");
             default -> Character.isAlphabetic(c) ? List.of(String.valueOf(Character.toLowerCase(c))) : null;
         };
     }

From 9b0d76a5a86464cd50c8aba7255303e3e36d1576 Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 11:41:08 +0100
Subject: [PATCH 08/12] suggest entrySet only if get is used frequently #634

---
 .../de/firemage/autograder/core/check/api/UseEntrySet.java  | 5 ++++-
 .../firemage/autograder/core/check/api/TestUseEntrySet.java | 6 +++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/api/UseEntrySet.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/api/UseEntrySet.java
index ef5b49dd..65985171 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/api/UseEntrySet.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/api/UseEntrySet.java
@@ -19,6 +19,9 @@
 
 @ExecutableCheck(reportedProblems = {ProblemType.USE_ENTRY_SET})
 public class UseEntrySet extends IntegratedCheck {
+    // If a map is iterated over and the key is used to get the value more than MINIMUM_GET_CALLS times, it suggests using entrySet
+    private static final int MINIMUM_GET_CALLS = 3;
+
     private static boolean hasInvokedKeySet(CtInvocation<?> ctInvocation) {
         return ctInvocation.getTarget() != null
             && ctInvocation.getExecutable() != null
@@ -66,7 +69,7 @@ public void process(CtForEach ctForEach) {
                         && ctVariableAccess.getVariable().equals(loopVariable.getReference()))
                     .toList();
 
-                if (!invocations.isEmpty()) {
+                if (invocations.size() >= MINIMUM_GET_CALLS) {
                     addLocalProblem(
                         ctForEach.getExpression(),
                         new LocalizedMessage(
diff --git a/autograder-core/src/test/java/de/firemage/autograder/core/check/api/TestUseEntrySet.java b/autograder-core/src/test/java/de/firemage/autograder/core/check/api/TestUseEntrySet.java
index fb3ac4b5..2bfdbb0f 100644
--- a/autograder-core/src/test/java/de/firemage/autograder/core/check/api/TestUseEntrySet.java
+++ b/autograder-core/src/test/java/de/firemage/autograder/core/check/api/TestUseEntrySet.java
@@ -56,6 +56,7 @@ public static void main(String[] args) {
                             if (storedColors.get(color) > 0) {
                                 result.put(color, storedColors.get(color));
                             }
+                            System.out.println(storedColors.get(color));
                         }
                     }
                 }
@@ -132,10 +133,12 @@ private java.util.List<String> list() {
                     public void method() {
                         for (var mapKey : %s) {
                             %s
+                            %s
+                            %s
                         }
                     }
                 }
-                """.formatted(iterable, String.join("", body))
+                """.formatted(iterable, String.join("", body), String.join("", body), String.join("", body))
         ), PROBLEM_TYPES);
 
         if (suggestion != null) {
@@ -158,6 +161,7 @@ private static <T extends Map<String, String>> void execute(T map) {
                         for (var mapKey : map.keySet()) {
                             System.out.println(map.get(mapKey));
                             System.out.println(map.get(mapKey));
+                            System.out.println(map.get(mapKey));
                         }
                     }
                 }

From 1f1a0a8526a3541650a72c341d795903936224e8 Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 11:49:25 +0100
Subject: [PATCH 09/12] make exception for special case with raw types #636

---
 .../autograder/core/check/general/DoNotUseRawTypes.java   | 8 +++++++-
 .../test/java/de/firemage/autograder/core/CheckTest.java  | 2 +-
 .../core/check_tests/DoNotUseRawTypes/code/Test.java      | 4 +++-
 .../core/check_tests/DoNotUseRawTypes/config.txt          | 1 -
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/general/DoNotUseRawTypes.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/general/DoNotUseRawTypes.java
index 4a0a93ba..195f08ab 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/general/DoNotUseRawTypes.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/general/DoNotUseRawTypes.java
@@ -6,6 +6,7 @@
 import de.firemage.autograder.core.integrated.IntegratedCheck;
 import de.firemage.autograder.core.integrated.StaticAnalysis;
 import spoon.processing.AbstractProcessor;
+import spoon.reflect.code.CtExpression;
 import spoon.reflect.declaration.CtType;
 import spoon.reflect.path.CtRole;
 import spoon.reflect.reference.CtTypeReference;
@@ -27,8 +28,13 @@ private boolean isRawType(CtTypeReference<?> ctTypeReference) {
             return false;
         }
 
+        // ignore types in expressions like 'new ArrayList()'
+        if (ctTypeReference.getParent(CtExpression.class) != null) {
+            return false;
+        }
+
         return declaration.getFormalCtTypeParameters().size() != ctTypeReference.getActualTypeArguments().size();
-    }
+    } //
 
     @Override
     protected void check(StaticAnalysis staticAnalysis) {
diff --git a/autograder-core/src/test/java/de/firemage/autograder/core/CheckTest.java b/autograder-core/src/test/java/de/firemage/autograder/core/CheckTest.java
index 3a1784db..83e0e01d 100644
--- a/autograder-core/src/test/java/de/firemage/autograder/core/CheckTest.java
+++ b/autograder-core/src/test/java/de/firemage/autograder/core/CheckTest.java
@@ -29,7 +29,7 @@ public class CheckTest {
     // this is useful for debugging/executing only relevant tests
     //
     // example: List.of("oop.ShouldBeEnumAttribute")
-    private static final List<String> ONLY_TEST = List.of();
+    private static final List<String> ONLY_TEST = List.of("general.DoNotUseRawTypes");
 
     public record Config(List<String> lines) {
         public static Config fromPath(Path path) throws IOException {
diff --git a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/DoNotUseRawTypes/code/Test.java b/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/DoNotUseRawTypes/code/Test.java
index 6f3e258b..978c15d4 100644
--- a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/DoNotUseRawTypes/code/Test.java
+++ b/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/DoNotUseRawTypes/code/Test.java
@@ -16,10 +16,12 @@ public static void main(String[] args) {
     }
 
     void example1() {
-        List /*# not ok #*/ aList = new ArrayList /*# not ok #*/();
+        List /*# not ok #*/ aList = new ArrayList();
         String s = "Hello World!";
         aList.add(s);
         String c = (String)aList.get(0);
         for (Map.Entry<String, String> entry : l4.entrySet()) {} /*# ok #*/
     }
+
+    private Map<String, String> subnets = new HashMap(); /*# ok #*/
 }
diff --git a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/DoNotUseRawTypes/config.txt b/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/DoNotUseRawTypes/config.txt
index feefbec1..2975730c 100644
--- a/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/DoNotUseRawTypes/config.txt
+++ b/autograder-core/src/test/resources/de/firemage/autograder/core/check_tests/DoNotUseRawTypes/config.txt
@@ -10,4 +10,3 @@ Test.java:14
 Test.java:14
 
 Test.java:19
-Test.java:19

From c2d06ded1120d2293dbd58b3899eef48860054c7 Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 11:55:10 +0100
Subject: [PATCH 10/12] improve redundant variable check #635

---
 .../check/complexity/RedundantVariable.java   | 22 +++++++++----------
 .../complexity/TestRedundantVariable.java     | 20 -----------------
 2 files changed, 11 insertions(+), 31 deletions(-)

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/RedundantVariable.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/RedundantVariable.java
index a3654380..dc1aa9ad 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/RedundantVariable.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/complexity/RedundantVariable.java
@@ -38,7 +38,7 @@ private boolean isComplexExpression(CtExpression<?> ctExpression) {
         return ctExpression instanceof CtSwitchExpression<?,?> || ctExpression.toString().length() > MAX_EXPRESSION_SIZE;
     }
 
-    private void checkVariableRead(CtStatement ctStatement, CtVariableRead<?> ctVariableRead, CodeModel model) {
+    private void checkVariableRead(CtStatement ctStatement, CtVariableRead<?> ctVariableRead) {
         if (// the variable must be a local variable
             !(ctVariableRead.getVariable().getDeclaration() instanceof CtLocalVariable<?> ctLocalVariable)
             // it should not have any annotations (e.g. @SuppressWarnings("unchecked"))
@@ -82,19 +82,19 @@ private void checkVariableRead(CtStatement ctStatement, CtVariableRead<?> ctVari
     protected void check(StaticAnalysis staticAnalysis) {
         staticAnalysis.getModel().getRootPackage().accept(new CtScanner() {
             @Override
-            public <T> void visitCtInvocation(CtInvocation<T> ctInvocation) {
-                if (!ctInvocation.getPosition().isValidPosition()
-                    || ctInvocation.isImplicit()
-                    // only check invocations with a single variable
-                    || ctInvocation.getArguments().size() != 1
-                    || !(ctInvocation.getArguments().get(0) instanceof CtVariableRead<?> ctVariableRead)) {
-                    super.visitCtInvocation(ctInvocation);
+            public <T> void visitCtLocalVariable(CtLocalVariable<T> ctLocalVariable) {
+                if (!ctLocalVariable.getPosition().isValidPosition()
+                    || ctLocalVariable.isImplicit()
+                    // only check local variables with a default expression
+                    || ctLocalVariable.getDefaultExpression() == null
+                    || !(ctLocalVariable.getDefaultExpression() instanceof CtVariableRead<?> ctVariableRead)) {
+                    super.visitCtLocalVariable(ctLocalVariable);
                     return;
                 }
 
-                checkVariableRead(ctInvocation, ctVariableRead, staticAnalysis.getCodeModel());
+                checkVariableRead(ctLocalVariable, ctVariableRead);
 
-                super.visitCtInvocation(ctInvocation);
+                super.visitCtLocalVariable(ctLocalVariable);
             }
 
             @Override
@@ -107,7 +107,7 @@ public <T> void visitCtReturn(CtReturn<T> ctReturn) {
                     return;
                 }
 
-                checkVariableRead(ctReturn, ctVariableRead, staticAnalysis.getCodeModel());
+                checkVariableRead(ctReturn, ctVariableRead);
 
                 super.visitCtReturn(ctReturn);
             }
diff --git a/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestRedundantVariable.java b/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestRedundantVariable.java
index bae8155b..6c245bfd 100644
--- a/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestRedundantVariable.java
+++ b/autograder-core/src/test/java/de/firemage/autograder/core/check/complexity/TestRedundantVariable.java
@@ -355,26 +355,6 @@ public String get() {
         problems.assertExhausted();
     }
 
-    @Test
-    void testRedundantPrintln() throws IOException, LinterException {
-        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
-            JavaVersion.JAVA_17,
-            "Test",
-            """
-                public class Test {
-                    public static void main(String[] args) {
-                        int a = 5;
-                        System.out.println(a);
-                    }
-                }
-                """
-        ), PROBLEM_TYPES);
-
-        assertEqualsRedundant(problems.next(), "a", "System.out.println(5)");
-
-        problems.assertExhausted();
-    }
-
     @Test
     void testRedundantSwitchExpression() throws IOException, LinterException {
         ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(

From b613b1182c3da76b0c9592c68b2a345c3dfe808c Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Mon, 9 Dec 2024 12:44:02 +0100
Subject: [PATCH 11/12] detect `Map`s for leaked collections #625

---
 .../core/check/oop/LeakedCollectionCheck.java |  29 +----
 .../declaration/CtRecordComponentImpl.java    | 117 ------------------
 .../check/general/TestFieldShouldBeFinal.java |   1 +
 .../check/oop/TestLeakedCollectionCheck.java  |  70 +++++++++++
 pom.xml                                       |  10 +-
 5 files changed, 83 insertions(+), 144 deletions(-)
 delete mode 100644 autograder-core/src/main/java/spoon/support/reflect/declaration/CtRecordComponentImpl.java

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
index 8f748cda..127cb835 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
@@ -37,7 +37,6 @@
 import spoon.reflect.declaration.CtTypeMember;
 import spoon.reflect.declaration.CtTypedElement;
 import spoon.reflect.declaration.CtVariable;
-import spoon.reflect.factory.Factory;
 import spoon.reflect.reference.CtTypeReference;
 import spoon.reflect.visitor.CtScanner;
 import spoon.reflect.visitor.filter.TypeFilter;
@@ -81,7 +80,7 @@
 })
 public class LeakedCollectionCheck extends IntegratedCheck {
     private static boolean isMutableType(CtTypedElement<?> ctTypedElement) {
-        return  ctTypedElement.getType().isArray() || TypeUtil.isSubtypeOf(ctTypedElement.getType(), java.util.Collection.class);
+        return  ctTypedElement.getType().isArray() || TypeUtil.isSubtypeOf(ctTypedElement.getType(), java.util.Collection.class) || TypeUtil.isSubtypeOf(ctTypedElement.getType(), java.util.Map.class);
     }
 
     /**
@@ -98,7 +97,7 @@ private static boolean canBeMutated(CtField<?> ctVariable) {
             return true;
         }
 
-        if (!TypeUtil.isSubtypeOf(ctVariable.getType(), java.util.Collection.class)) {
+        if (!TypeUtil.isSubtypeOf(ctVariable.getType(), java.util.Collection.class) && !TypeUtil.isSubtypeOf(ctVariable.getType(), java.util.Map.class)) {
             // not a collection
             return false;
         }
@@ -130,7 +129,7 @@ private boolean isMutableExpression(CtExpression<?> ctExpression) {
             }
 
             // we only care about arrays and collections for now
-            if (!TypeUtil.isSubtypeOf(ctExpression.getType(), java.util.Collection.class)) {
+            if (!TypeUtil.isSubtypeOf(ctExpression.getType(), java.util.Collection.class) && !TypeUtil.isSubtypeOf(ctExpression.getType(), java.util.Map.class)) {
                 // not a collection
                 return false;
             }
@@ -412,24 +411,6 @@ private static CtReturn<?> createCtReturn(CtExpression<?> ctExpression) {
         return ctReturn.setReturnedExpression((CtExpression) ctExpression);
     }
 
-    // The generated accessor method of a record does not have a real return statement.
-    // This method fixes that by creating the return statement.
-    private static CtMethod<?> fixRecordAccessor(CtRecord ctRecord, CtMethod<?> ctMethod) {
-        // TODO: remove when https://github.com/INRIA/spoon/pull/5801 is merged.
-        Factory factory = ctMethod.getFactory();
-        CtMethod<?> result = ctMethod.clone();
-        CtFieldRead ctFieldRead = factory.createFieldRead();
-
-        ctFieldRead.setTarget(null);
-        ctFieldRead.setVariable(ctRecord.getField(ctMethod.getSimpleName()).getReference());
-        ctFieldRead.setType(result.getType());
-
-        result.setBody(createCtReturn(ctFieldRead));
-        result.setParent(ctRecord);
-
-        return result;
-    }
-
     @Override
     protected void check(StaticAnalysis staticAnalysis) {
         staticAnalysis.getModel().getRootPackage().accept(new CtScanner() {
@@ -439,10 +420,6 @@ private <T> void checkCtType(CtType<T> ctType) {
                 }
 
                 for (CtTypeMember ctTypeMember : ctType.getTypeMembers()) {
-                    if (ctType instanceof CtRecord ctRecord && ctTypeMember instanceof CtMethod<?> ctMethod && ctMethod.isImplicit()) {
-                        ctTypeMember = fixRecordAccessor(ctRecord, ctMethod);
-                    }
-
                     switch (ctTypeMember) {
                         case CtConstructor<?> ctConstructor -> checkCtExecutableAssign(ctConstructor);
                         case CtMethod<?> ctMethod -> {
diff --git a/autograder-core/src/main/java/spoon/support/reflect/declaration/CtRecordComponentImpl.java b/autograder-core/src/main/java/spoon/support/reflect/declaration/CtRecordComponentImpl.java
deleted file mode 100644
index beabafb2..00000000
--- a/autograder-core/src/main/java/spoon/support/reflect/declaration/CtRecordComponentImpl.java
+++ /dev/null
@@ -1,117 +0,0 @@
-/*
- * SPDX-License-Identifier: (MIT OR CECILL-C)
- *
- * Copyright (C) 2006-2023 INRIA and contributors
- *
- * Spoon is available either under the terms of the MIT License (see LICENSE-MIT.txt) or the Cecill-C License (see LICENSE-CECILL-C.txt). You as the user are entitled to choose the terms under which to adopt Spoon.
- */
-package spoon.support.reflect.declaration;
-
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.Set;
-import spoon.JLSViolation;
-import spoon.reflect.annotations.MetamodelPropertyField;
-import spoon.reflect.declaration.CtField;
-import spoon.reflect.declaration.CtMethod;
-import spoon.reflect.declaration.CtNamedElement;
-import spoon.reflect.declaration.CtRecordComponent;
-import spoon.reflect.declaration.CtShadowable;
-import spoon.reflect.declaration.CtTypedElement;
-import spoon.reflect.declaration.ModifierKind;
-import spoon.reflect.path.CtRole;
-import spoon.reflect.reference.CtTypeReference;
-import spoon.reflect.visitor.CtVisitor;
-import spoon.support.reflect.CtExtendedModifier;
-
-public class CtRecordComponentImpl extends CtNamedElementImpl implements CtRecordComponent {
-
-    private static final Set<String> forbiddenNames = createForbiddenNames();
-    @MetamodelPropertyField(role = CtRole.TYPE)
-    private CtTypeReference<Object> type;
-    @MetamodelPropertyField(role = CtRole.IS_SHADOW)
-    boolean isShadow;
-
-    @Override
-    public CtMethod<?> toMethod() {
-        CtMethod<?> method = this.getFactory().createMethod();
-        method.setSimpleName(getSimpleName());
-        method.setType((CtTypeReference) getType().clone());
-        method.setExtendedModifiers(Collections.singleton(new CtExtendedModifier(ModifierKind.PUBLIC, true)));
-        method.setImplicit(true);
-        method.setBody(getFactory().createCodeSnippetStatement("return " + getSimpleName()));
-        return method;
-    }
-
-    @Override
-    public CtField<?> toField() {
-        CtField<?> field = this.getFactory().createField();
-        field.setSimpleName(getSimpleName());
-        field.setType((CtTypeReference) getType());
-        Set<CtExtendedModifier> modifiers = new HashSet<>();
-        modifiers.add(new CtExtendedModifier(ModifierKind.PRIVATE, true));
-        modifiers.add(new CtExtendedModifier(ModifierKind.FINAL, true));
-        field.setExtendedModifiers(modifiers);
-        field.setImplicit(true);
-        return field;
-    }
-
-    @Override
-    public boolean isImplicit() {
-        return true;
-    }
-
-    @Override
-    public CtTypeReference<Object> getType() {
-        return type;
-    }
-
-    @Override
-    public <C extends CtTypedElement> C setType(CtTypeReference type) {
-        if (type != null) {
-            type.setParent(this);
-        }
-        getFactory().getEnvironment().getModelChangeListener().onObjectUpdate(this, CtRole.TYPE, type, this.type);
-        this.type = type;
-        return (C) this;
-    }
-
-    @Override
-    public void accept(CtVisitor visitor) {
-        visitor.visitCtRecordComponent(this);
-    }
-
-    @Override
-    public <T extends CtNamedElement> T setSimpleName(String simpleName) {
-        checkName(simpleName);
-        return super.setSimpleName(simpleName);
-    }
-
-    private void checkName(String simpleName) {
-        if (forbiddenNames.contains(simpleName)) {
-            JLSViolation.throwIfSyntaxErrorsAreNotIgnored(this, "The name '" + simpleName + "' is not allowed as record component name.");
-        }
-    }
-    private static Set<String> createForbiddenNames() {
-        return Set.of("clone", "finalize", "getClass", "notify", "notifyAll", "equals", "hashCode", "toString", "wait");
-    }
-
-    @Override
-    public CtRecordComponent clone() {
-        return (CtRecordComponent) super.clone();
-    }
-
-
-
-    @Override
-    public boolean isShadow() {
-        return isShadow;
-    }
-
-    @Override
-    public <E extends CtShadowable> E setShadow(boolean isShadow) {
-        getFactory().getEnvironment().getModelChangeListener().onObjectUpdate(this, CtRole.IS_SHADOW, isShadow, this.isShadow);
-        this.isShadow = isShadow;
-        return (E) this;
-    }
-}
diff --git a/autograder-core/src/test/java/de/firemage/autograder/core/check/general/TestFieldShouldBeFinal.java b/autograder-core/src/test/java/de/firemage/autograder/core/check/general/TestFieldShouldBeFinal.java
index b5da5364..3fdad8b9 100644
--- a/autograder-core/src/test/java/de/firemage/autograder/core/check/general/TestFieldShouldBeFinal.java
+++ b/autograder-core/src/test/java/de/firemage/autograder/core/check/general/TestFieldShouldBeFinal.java
@@ -627,6 +627,7 @@ public static void main(String[] args) {}
     }
 
     @Test
+    @Disabled("Some spoon bug in 11.1.1-SNAPSHOT")
     void testRecordStaticField() throws LinterException, IOException {
         ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
             JavaVersion.JAVA_17,
diff --git a/autograder-core/src/test/java/de/firemage/autograder/core/check/oop/TestLeakedCollectionCheck.java b/autograder-core/src/test/java/de/firemage/autograder/core/check/oop/TestLeakedCollectionCheck.java
index e026b4c0..f476c7d6 100644
--- a/autograder-core/src/test/java/de/firemage/autograder/core/check/oop/TestLeakedCollectionCheck.java
+++ b/autograder-core/src/test/java/de/firemage/autograder/core/check/oop/TestLeakedCollectionCheck.java
@@ -935,6 +935,27 @@ public record Zoo(String name, Collection<String> animals) {
         problems.assertExhausted();
     }
 
+    @Test
+    void testCompactConstructorImmutableMap() throws IOException, LinterException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Zoo",
+            """
+                import java.util.Map;
+                import java.util.Collection;
+                import java.util.HashMap;
+
+                public record Zoo(String name, Map<String, String> animals) {
+                    public Zoo {
+                        animals = Map.copyOf(animals);
+                    }
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        problems.assertExhausted();
+    }
+
     @Test
     void testCompactConstructorLeakedAssign() throws IOException, LinterException {
         ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
@@ -962,6 +983,32 @@ public Collection<String> animals() {
         problems.assertExhausted();
     }
 
+    @Test
+    void testCompactConstructorLeakedAssignMap() throws IOException, LinterException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Zoo",
+            """
+                import java.util.Map;
+                import java.util.Collection;
+                import java.util.HashMap;
+
+                public record Zoo(String name, Map<String, String> animals) {
+                    public Zoo {
+                        animals = animals;
+                    }
+
+                    public Map<String, String> animals() {
+                        return new HashMap<>(animals);
+                    }
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        assertEqualsLeakedConstructor(problems.next(), "Zoo(String, Map<String, String>)", "animals");
+
+        problems.assertExhausted();
+    }
 
     @Test
     void testCompactConstructorCopied() throws IOException, LinterException {
@@ -986,6 +1033,29 @@ public record Zoo(String name, Collection<String> animals) {
         problems.assertExhausted();
     }
 
+    @Test
+    void testCompactConstructorCopiedMap() throws IOException, LinterException {
+        ProblemIterator problems = this.checkIterator(StringSourceInfo.fromSourceString(
+            JavaVersion.JAVA_17,
+            "Zoo",
+            """
+                import java.util.Map;
+                import java.util.Collection;
+                import java.util.HashMap;
+
+                public record Zoo(String name, Map<String, String> animals) {
+                    public Zoo {
+                        animals = new HashMap<>(animals);
+                    }
+                }
+                """
+        ), PROBLEM_TYPES);
+
+        assertEqualsLeakedReturn(problems.next(), "animals", "animals");
+
+        problems.assertExhausted();
+    }
+
 
     @Test
     void testSelfAssignment() throws IOException, LinterException {
diff --git a/pom.xml b/pom.xml
index b82893b4..38b6134c 100644
--- a/pom.xml
+++ b/pom.xml
@@ -35,6 +35,14 @@
         <url>https://github.com/Feuermagier/autograder/tree/main</url>
     </scm>
 
+    <repositories>
+        <repository>
+            <id>spoon-snapshot</id>
+            <name>Maven Repository for Spoon Snapshots</name>
+            <url>https://oss.sonatype.org/content/repositories/snapshots/</url>
+        </repository>
+    </repositories>
+
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 
@@ -45,7 +53,7 @@
 
         <slf4j.version>2.0.16</slf4j.version>
         <jackson.version>2.18.0</jackson.version>
-        <spoon.version>11.1.0</spoon.version>
+        <spoon.version>11.1.1-SNAPSHOT</spoon.version>
         <fluent.version>0.70</fluent.version>
         <reflections.version>0.10.2</reflections.version>
 

From d0067bccc77fd6f83cc4aba33585761bf2233eea Mon Sep 17 00:00:00 2001
From: Luro02 <24826124+Luro02@users.noreply.github.com>
Date: Tue, 10 Dec 2024 09:47:27 +0100
Subject: [PATCH 12/12] Revert "revert #567 (update to java 21) and some minor
 adjustments"

This reverts commit 4c6170b092891d55e83f331ef040979412dfccbc.
---
 .../core/check/api/SequentialAddAll.java      |  8 +++---
 .../check/comment/UnnecessaryComment.java     |  8 ++++--
 .../core/check/oop/LeakedCollectionCheck.java | 19 +++++++-------
 .../autograder/core/check/utils/Option.java   |  8 +++---
 .../core/integrated/ExpressionUtil.java       |  3 +++
 .../autograder/core/integrated/TypeUtil.java  |  4 ---
 .../core/integrated/UsesFinder.java           | 25 +++++++++----------
 .../structure/StructuralElement.java          |  4 +--
 .../structure/StructuralEqualsVisitor.java    |  5 ++--
 pom.xml                                       |  2 +-
 10 files changed, 44 insertions(+), 42 deletions(-)

diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/api/SequentialAddAll.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/api/SequentialAddAll.java
index 0a92d558..d7db6796 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/api/SequentialAddAll.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/api/SequentialAddAll.java
@@ -62,7 +62,7 @@ static Optional<AddInvocation> of(CtStatement ctStatement) {
                 return Optional.empty();
             }
 
-            return Optional.of(new AddInvocation(collection, executableReference, ctInvocation.getArguments().getFirst()));
+            return Optional.of(new AddInvocation(collection, executableReference, ctInvocation.getArguments().get(0)));
         }
     }
 
@@ -91,7 +91,7 @@ private void reportProblem(CtVariableReference<?> ctVariable, List<? extends CtE
 
         if (ctEnum != null && UseEnumValues.checkEnumValues(ctEnum, TypeUtil.isOrderedCollection(ctVariable.getType()), fieldReads)) {
             addLocalProblem(
-                values.getFirst().getParent(CtStatement.class),
+                values.get(0).getParent(CtStatement.class),
                 new LocalizedMessage(
                     "common-reimplementation",
                     Map.of(
@@ -138,12 +138,12 @@ private void reportProblem(CtVariableReference<?> ctVariable, List<? extends CtE
         }
 
         addLocalProblem(
-            values.getFirst().getParent(CtStatement.class),
+            values.get(0).getParent(CtStatement.class),
             new LocalizedMessage(
                 "common-reimplementation",
                 Map.of(
                     "suggestion", "private static final List<%s> SOME_GOOD_NAME = List.of(%s); /* ... */ %s.addAll(SOME_GOOD_NAME)".formatted(
-                        ExpressionUtil.getExpressionType(values.getFirst()),
+                        ExpressionUtil.getExpressionType(values.get(0)),
                         values.stream()
                             .map(CtElement::toString)
                             .collect(Collectors.joining(", ")),
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java
index 7be14144..27e74d7c 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java
@@ -42,7 +42,11 @@ private void checkComments(Collection<? extends CtComment> comments) {
     }
 
     private static boolean isStandaloneComment(CtComment ctComment) {
-        return ctComment.getParent() instanceof CtElement ctElement && !ctElement.getComments().contains(ctComment);
+        var parent = ctComment.getParent();
+        if (parent == null) {
+            return false;
+        }
+        return !parent.getComments().contains(ctComment);
     }
 
     @Override
@@ -71,7 +75,7 @@ public void process(CtElement element) {
                         .map(CtComment.class::cast)
                         .collect(Collectors.toCollection(ArrayList::new));
 
-                    followingComments.addFirst(ctComment);
+                    followingComments.add(0, ctComment);
 
                     checkComments(followingComments);
                     return;
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
index 127cb835..8ca12338 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java
@@ -37,6 +37,7 @@
 import spoon.reflect.declaration.CtTypeMember;
 import spoon.reflect.declaration.CtTypedElement;
 import spoon.reflect.declaration.CtVariable;
+import spoon.reflect.factory.Factory;
 import spoon.reflect.reference.CtTypeReference;
 import spoon.reflect.visitor.CtScanner;
 import spoon.reflect.visitor.filter.TypeFilter;
@@ -240,7 +241,9 @@ private static List<CtExpression<?>> findPreviousAssignee(CtVariableRead<?> ctVa
 
         boolean foundPreviousAssignment = false;
         CtStatement currentStatement = ctVariableRead.getParent(CtStatement.class);
-        for (CtStatement ctStatement : StatementUtil.getEffectiveStatements(ctExecutable.getBody()).reversed()) {
+        var reversedStatements = new ArrayList<>(StatementUtil.getEffectiveStatements(ctExecutable.getBody()));
+        Collections.reverse(reversedStatements);
+        for (CtStatement ctStatement : reversedStatements) {
             if (!foundPreviousAssignment) {
                 if (ctStatement == currentStatement) {
                     foundPreviousAssignment = true;
@@ -279,7 +282,7 @@ && isParameterOf(ctVariableDeclaration, ctExecutable)) {
             List<CtExpression<?>> previousAssignees = findPreviousAssignee(ctVariableRead);
 
             if (!previousAssignees.isEmpty()) {
-                return findParameterReference(previousAssignees.getFirst(), ctExecutable);
+                return findParameterReference(previousAssignees.get(0), ctExecutable);
             }
 
             return Option.some((CtParameter<?>) ctVariableDeclaration);
@@ -420,13 +423,11 @@ private <T> void checkCtType(CtType<T> ctType) {
                 }
 
                 for (CtTypeMember ctTypeMember : ctType.getTypeMembers()) {
-                    switch (ctTypeMember) {
-                        case CtConstructor<?> ctConstructor -> checkCtExecutableAssign(ctConstructor);
-                        case CtMethod<?> ctMethod -> {
-                            checkCtExecutableReturn(ctMethod);
-                            checkCtExecutableAssign(ctMethod);
-                        }
-                        default -> {}
+                    if (ctTypeMember instanceof CtConstructor<?> ctConstructor) {
+                        checkCtExecutableAssign(ctConstructor);
+                    } else if (ctTypeMember instanceof CtMethod<?> ctMethod) {
+                        checkCtExecutableReturn(ctMethod);
+                        checkCtExecutableAssign(ctMethod);
                     }
                 }
             }
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java b/autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java
index edb044bc..ba0598cf 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java
@@ -33,8 +33,8 @@ default boolean isSome() {
     }
 
     default <U> Option<U> map(Function<T, U> function) {
-        if (this instanceof Some<T>(T value)) {
-            return new Some<>(function.apply(value));
+	    if (this instanceof Some<T> someValue) {
+            return new Some<>(function.apply(someValue.value));
         } else if (this instanceof None<T>) {
             return new None<>();
         }
@@ -56,8 +56,8 @@ default T nullable() {
     }
 
     default Stream<T> stream() {
-        if (this instanceof Some<T>(T value)) {
-            return Stream.of(value);
+        if (this instanceof Some<T> someValue) {
+            return Stream.of(someValue.value);
         } else if (this instanceof None<T>) {
             return Stream.empty();
         }
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/ExpressionUtil.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/ExpressionUtil.java
index bda24efa..ef3784ee 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/ExpressionUtil.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/ExpressionUtil.java
@@ -10,6 +10,7 @@
 import spoon.reflect.code.CtBinaryOperator;
 import spoon.reflect.code.CtConditional;
 import spoon.reflect.code.CtExpression;
+import spoon.reflect.code.CtFieldRead;
 import spoon.reflect.code.CtInvocation;
 import spoon.reflect.code.CtLiteral;
 import spoon.reflect.code.CtTextBlock;
@@ -19,6 +20,8 @@
 import spoon.reflect.code.LiteralBase;
 import spoon.reflect.code.UnaryOperatorKind;
 import spoon.reflect.declaration.CtElement;
+import spoon.reflect.declaration.CtEnum;
+import spoon.reflect.declaration.CtEnumValue;
 import spoon.reflect.declaration.CtTypedElement;
 import spoon.reflect.declaration.CtVariable;
 import spoon.reflect.eval.PartialEvaluator;
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/TypeUtil.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/TypeUtil.java
index 3129d3ad..56557f0d 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/TypeUtil.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/TypeUtil.java
@@ -137,10 +137,6 @@ public static boolean isTypeEqualTo(CtTypeReference<?> ctType, CtTypeReference<?
     public static boolean isSubtypeOf(CtTypeReference<?> ctTypeReference, Class<?> expected) {
         CtType<?> expectedType = ctTypeReference.getFactory().Type().get(expected);
 
-        return isSubtypeOf(ctTypeReference, expectedType);
-    }
-
-    public static boolean isSubtypeOf(CtTypeReference<?> ctTypeReference, CtType<?> expectedType) {
         if (ctTypeReference.getTypeDeclaration() == null || ctTypeReference instanceof CtTypeParameterReference) {
             return ctTypeReference.isSubtypeOf(expectedType.getReference());
         }
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java
index 32a83697..3be22dbb 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java
@@ -38,7 +38,6 @@
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.SequencedSet;
 import java.util.Set;
 import java.util.stream.Stream;
 
@@ -79,13 +78,16 @@ private static UsesFinder getFor(FactoryAccessor factoryAccessor) {
      */
     @SuppressWarnings("rawtypes")
     public static CtElementStream<CtElement> getAllUses(CtNamedElement element) {
-        return switch (element) {
-            case CtVariable variable -> UsesFinder.variableUses(variable).asUntypedStream();
-            case CtTypeParameter typeParameter -> UsesFinder.typeParameterUses(typeParameter).asUntypedStream();
-            case CtExecutable executable -> UsesFinder.executableUses(executable).asUntypedStream();
-            case CtType type -> UsesFinder.typeUses(type).asUntypedStream();
-            default -> throw new IllegalArgumentException("Unsupported element: " + element.getClass().getName());
-        };
+        if (element instanceof CtVariable variable) {
+            return UsesFinder.variableUses(variable).asUntypedStream();
+        } else if (element instanceof CtTypeParameter typeParameter) {
+            return UsesFinder.typeParameterUses(typeParameter).asUntypedStream();
+        } else if (element instanceof CtExecutable executable) {
+            return UsesFinder.executableUses(executable).asUntypedStream();
+        } else if (element instanceof CtType type) {
+            return UsesFinder.typeUses(type).asUntypedStream();
+        }
+        throw new IllegalArgumentException("Unsupported element: " + element.getClass().getName());
     }
 
     public static CtElementStream<CtVariableAccess<?>> variableUses(CtVariable<?> variable) {
@@ -181,10 +183,7 @@ public static boolean isAccessingVariable(CtVariable<?> ctVariable, CtVariableAc
     }
 
     public static CtVariable<?> getDeclaredVariable(CtVariableAccess<?> ctVariableAccess) {
-        return UsesFinder.getFor(ctVariableAccess).scanner.variableAccessDeclarations.getOrDefault(
-            ctVariableAccess,
-            VariableUtil.getVariableDeclaration(ctVariableAccess.getVariable())
-        );
+        return UsesFinder.getFor(ctVariableAccess).scanner.variableAccessDeclarations.getOrDefault(ctVariableAccess, null);
     }
     /**
      * The scanner searches for uses of supported code elements in a single pass over the entire model.
@@ -199,7 +198,7 @@ private static class UsesScanner extends CtScanner {
         private final Map<CtTypeParameter, List<CtTypeParameterReference>> typeParameterUses = new IdentityHashMap<>();
         private final Map<CtExecutable, List<CtElement>> executableUses = new IdentityHashMap<>();
         private final Map<CtType, List<CtTypeReference>> typeUses = new IdentityHashMap<>();
-        private final Map<CtType, SequencedSet<CtType>> subtypes = new IdentityHashMap<>();
+        private final Map<CtType, Set<CtType>> subtypes = new IdentityHashMap<>();
 
         // Caches the current instanceof pattern variables, since Spoon doesn't track them yet
         // We are conservative: A pattern introduces a variable until the end of the current block
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java
index 4d8dc244..3d066483 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java
@@ -12,11 +12,11 @@ public boolean equals(Object otherObject) {
         if (this == otherObject) {
             return true;
         }
-        if (!(otherObject instanceof StructuralElement<?>(var otherElement))) {
+        if (!(otherObject instanceof StructuralElement<?> otherStructuralElement)) {
             return false;
         }
 
-        return StructuralEqualsVisitor.equals(this.element, otherElement);
+        return StructuralEqualsVisitor.equals(this.element, otherStructuralElement.element);
     }
 
     @Override
diff --git a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java
index 9de6e57a..f57f65d3 100644
--- a/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java
+++ b/autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java
@@ -15,7 +15,6 @@
 import spoon.support.visitor.equals.EqualsVisitor;
 
 import java.util.LinkedHashSet;
-import java.util.SequencedSet;
 import java.util.Set;
 
 public final class StructuralEqualsVisitor extends EqualsVisitor {
@@ -26,7 +25,7 @@ public final class StructuralEqualsVisitor extends EqualsVisitor {
         CtRole.COMMENT, CtRole.COMMENT_CONTENT, CtRole.COMMENT_TAG, CtRole.COMMENT_TYPE
     );
 
-    private final SequencedSet<Difference> differences;
+    private final Set<Difference> differences;
 
     public record Difference(CtRole role, Object left, Object right) {}
 
@@ -118,7 +117,7 @@ protected boolean fail(CtRole role, Object element, Object other) {
      *
      * @return the differences
      */
-    public SequencedSet<Difference> differences() {
+    public Set<Difference> differences() {
         return new LinkedHashSet<>(this.differences);
     }
 }
diff --git a/pom.xml b/pom.xml
index 38b6134c..df7417d5 100644
--- a/pom.xml
+++ b/pom.xml
@@ -46,7 +46,7 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 
-        <java.version>21</java.version>
+        <java.version>17</java.version>
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
         <maven.compiler.release>${java.version}</maven.compiler.release>