add DukeExceptions and handling

src/main/java/Duke.java

@@ -1,8 +1,6 @@
 import java.util.Scanner;
 
 public class Duke {
-    public enum CommandStatus{ SUCCESS, FAIL }
-
     public static final int NUM_ARGS_DEADLINE = 2;
     public static final int NUM_ARGS_EVENT = 2;
 
@@ -15,47 +13,44 @@ public static void main(String[] args) {
         printHomeScreen();
 
         while(programIsRunning){
-            String[] input = new String[2];
+            String[] input;
             input = getInputSeparateCommandAndDescription();
 
             String command = input[0];
             String description = "";
-            if (input.length == 2)
+            if(input.length == 2)
                description = input[1];
 
-            CommandStatus commandResult = CommandStatus.FAIL;
-
-            switch(command) {
-            case "bye" :
-                commandResult = handleByeCommand();
-                break;
-            case "list" :
-                commandResult = handleListCommand();
-                break;
-            case "done" :
-                commandResult = handleDoneCommand(command, description);
-                break;
-            case "todo" : // Fallthrough
-            case "deadline" : // Fallthrough
-            case "event" :
-                commandResult = handleAddCommand(command, description);
-                break;
-            default :
-                System.out.println("I don't understand that command");
-                break;
-            }
-
-            if  (commandResult == CommandStatus.FAIL){
-                System.out.println("Command Failed");
+            try {
+                switch(command) {
+                case "bye":
+                    handleByeCommand();
+                    break;
+                case "list":
+                    handleListCommand();
+                    break;
+                case "done":
+                    handleDoneCommand(description);
+                    break;
+                case "todo": // Fallthrough
+                case "deadline": // Fallthrough
+                case "event":
+                    handleAddCommand(command, description);
+                    break;
+                default:
+                    throw new DukeException("Duke does not understand that command");
+                }
+            } catch(DukeException exception) {
+                handleException(exception);
             }
         }
         printExitScreen();
     }
 
     public static void printHomeScreen(){
         printLineSeparator();
-        System.out.println("Hello! I'm Duke");
-        System.out.println("What can I do for you?");
+        System.out.println("Hello! I'm Duke" + System.lineSeparator() +
+                            "What can I do for you?");
         printLineSeparator();
     }
 
@@ -68,69 +63,78 @@ public static void printLineSeparator(){
         System.out.println("---------------------------------------");
     }
 
-    public static CommandStatus handleByeCommand(){
+    public static void printSuccessfulAddEntry(Task newTask) {
+        printLineSeparator();
+
+        System.out.print("Got it. I've added this task:" + System.lineSeparator() +
+                "\t" + newTask + System.lineSeparator()
+                +"Now you have " + tasksListIndex + " task");
+
+        if(tasksListIndex > 1) {
+            System.out.print("s");
+        }
+
+        System.out.println(" in the list.");
+
+        printLineSeparator();
+    }
+
+    public static void handleByeCommand(){
         programIsRunning = false;
-        return CommandStatus.SUCCESS;
     }
 
     public static String[] getInputSeparateCommandAndDescription(){
         String input = scanner.nextLine();
         input = input.trim();
 
-        String[] commands = new String[2];
+        String[] commands;
         commands = input.split(" ", 2);
 
         return commands;
     }
 
-    public static CommandStatus handleListCommand() {
+    public static void handleListCommand() {
         int entryNum = 1;
 
         printLineSeparator();
 
-        for (Task task : tasksList) {
-            if (task == null) {
+        for(Task task : tasksList) {
+            if(task == null) {
                 break;
             } else {
-                System.out.print(String.valueOf(entryNum) + ".");
-                System.out.println(task);
+                System.out.println(entryNum + "." + task);
                 entryNum++;
             }
         }
 
         printLineSeparator();
-
-        return CommandStatus.SUCCESS;
     }
 
-
-        public static CommandStatus handleDoneCommand(String command, String description) {
-        if (description == null){
-            return CommandStatus.FAIL;
+    public static void handleDoneCommand(String description) throws DukeException{
+        if(description.equals("")){
+            throw new DukeException("The done command format is: done <taskDescription>");
         }
-        // Looks for a task with a matching description task to mark as done
-        for (Task task : tasksList) {
-            if (task == null) {
-                return CommandStatus.FAIL;
-            } else if (task.description.equals(description) && task.isDone == false) {
-                task.isDone = true;
 
+        // Looks for a task with matching the description task and marks it as done
+        for(Task task : tasksList) {
+            if(task == null) {
+                return;
+            } else if(task.description.equals(description) && !task.isDone ) {
+                task.isDone = true;
 
-                System.out.print("Nice! I've marked this task as done:\n\t");
-                System.out.println(task);
+                System.out.println("Nice! I've marked this task as done:" + System.lineSeparator() +
+                                    "\t" + task);
                 printLineSeparator();
 
-                return CommandStatus.SUCCESS;
+                return;
             }
         }
-
-        return CommandStatus.FAIL;
     }
 
-    public static CommandStatus handleAddCommand(String command, String description) {
+    public static void handleAddCommand(String command, String description) throws DukeException {
         Task newTask = null;
 
-        switch (command){
+        switch(command){
         case "todo" :
             newTask = createToDo(description);
             break;
@@ -144,53 +148,43 @@ public static CommandStatus handleAddCommand(String command, String description)
             break;
         }
 
-        if (newTask == null){
-            return  CommandStatus.FAIL;
+        if(newTask == null){
+            throw new DukeException("Unable to create the new Task");
         }
 
         tasksList[tasksListIndex] = newTask;
         tasksListIndex++;
 
         printSuccessfulAddEntry(newTask);
-
-        return CommandStatus.SUCCESS;
     }
 
-    public static Todo createToDo(String description){
+    public static void handleException(DukeException exception){
+        System.out.println("Exception!" + System.lineSeparator() +
+                            "\t" + exception.description);
+    }
+    public static Todo createToDo(String description) throws DukeException{
+        if (description.equals("")){
+            throw new DukeException("The todo format is: todo <desc>");
+        }
         return new Todo(description);
     }
 
-    public static Deadlines createDeadline(String description){
+    public static Deadlines createDeadline(String description) throws DukeException{
         String[] taskDetails = description.split(" /by ");
-        if (taskDetails.length < NUM_ARGS_DEADLINE){
-            return null;
+        if(taskDetails.length < NUM_ARGS_DEADLINE){
+            throw new DukeException("The deadline format is: deadline <desc> \\by <time>");
         }
 
         return new Deadlines(taskDetails[0], taskDetails[1]);
     }
 
-    public static Event createEvent(String description){
+    public static Event createEvent(String description) throws DukeException{
         String[] taskDetails = description.split(" /at ");
-        if (taskDetails.length < NUM_ARGS_DEADLINE){
-            return null;
+        if(taskDetails.length < NUM_ARGS_EVENT){
+            throw new DukeException("The event format is: event <desc> \\at <time>");
         }
 
         return new Event(taskDetails[0], taskDetails[1]);
     }
-
-    public static void printSuccessfulAddEntry(Task newTask) {
-        printLineSeparator();
 
-        System.out.print("Got it. I've added this task:" + System.lineSeparator() +
-                "\t" + newTask + System.lineSeparator()
-                +"Now you have " + tasksListIndex + " task");
-
-        if (tasksListIndex > 1) {
-            System.out.print("s");
-        }
-
-        System.out.println(" in the list.");
-
-        printLineSeparator();
-    }
 }

src/main/java/DukeException.java

@@ -0,0 +1,7 @@
+public class DukeException extends Exception{
+    String description;
+
+    public DukeException (String description){
+        this.description = description;
+    }
+}

text-ui-test/EXPECTED.TXT

@@ -2,8 +2,8 @@
 Hello! I'm Duke
 What can I do for you?
 ---------------------------------------
-I don't understand that command
-Command Failed
+Exception!
+	Duke does not understand that command
 ---------------------------------------
 ---------------------------------------
 ---------------------------------------
@@ -40,7 +40,8 @@ Nice! I've marked this task as done:
 2.[E][✘] 123 (at: 12pm)
 3.[D][✓] study (by: Sleeptime)
 ---------------------------------------
-Command Failed
+Exception!
+	The done command format is: done <taskDescription>
 ---------------------------------------
 1.[T][✓] 123
 2.[E][✘] 123 (at: 12pm)