Merge branch 'master' into branch-A-CodeQuality

src/main/java/duke/Duke.java

@@ -96,22 +96,28 @@ private String executeCommand(String userInput) throws DukeException {
         default:
             throw new UnsupportedOperationException(); // Error
         }
+        assert false; // Execution should not reach this point
         return "";
     }
 
     private String addNewTask(Task newTask) {
+        assert newTask != null; // Task to be added cannot be null
         tasks.addTask(newTask);
         storage.saveTasks(tasks);
         return ui.printAddTask(tasks, newTask);
     }
 
     private String completeTask(int taskNum) {
+        // TaskNum should be within 1 to the size of the TaskList
+        assert taskNum > 0 && taskNum <= tasks.getSize(): taskNum;
         tasks.completeTask(taskNum);
         storage.saveTasks(tasks);
         return ui.printCompleteTask(tasks.getTask(taskNum));
     }
 
     private String deleteTask(int taskNum) {
+        // TaskNum should be within 1 to the size of the TaskList
+        assert taskNum > 0 && taskNum <= tasks.getSize(): taskNum;
         Task deletedTask = tasks.deleteTask(taskNum);
         storage.saveTasks(tasks);
         return ui.printDeleteTask(tasks, deletedTask);

src/main/java/duke/Parser.java

@@ -81,7 +81,8 @@ public static Task parseNewTask(String userInput) throws MissingInputException {
 
             return new Event(eventName, eventDateTime);
         default:
-            return null; // Error
+            assert false; // Undefined task type input
+            return null;
         }
     }
 

src/main/java/duke/Storage.java

@@ -88,7 +88,7 @@ private Task loadTask(String savedTask) {
             loadedTask = new Event(taskDesc, eventDateTime, isTaskDone);
             break;
         default:
-            break; // Error
+            assert false; // Undefined task type input
         }
         saveDataScanner.close();