diff --git a/Testing.txt b/Testing.txt
index 7b6a0759ab..69d010a145 100644
--- a/Testing.txt
+++ b/Testing.txt
@@ -1,6 +1,3 @@
-[D][ ] work more on ip (by: Sep 22 2023)
-[E][ ] workout (from: Sep 22 2023 to: Sep 22 3023)
-[T][X] workout
-[T][ ] shower
-[D][ ] dry off (by: Sep 22 2023)
-[E][ ] change clothes (from: Sep 23 2023 to: Sep 23 2024)
\ No newline at end of file
+  [D][X] rk more on ip (by: Sep 22 2023)
+  [E][X] rkout (from: Sep 22 2023 to: Sep 22 3023)
+  [E][ ] ange clothes (from: Sep 23 2023 to: Sep 23 2024)
diff --git a/src/main/java/command/MultipleCommand.java b/src/main/java/command/MultipleCommand.java
index 160ef117a9..207975ed46 100644
--- a/src/main/java/command/MultipleCommand.java
+++ b/src/main/java/command/MultipleCommand.java
@@ -39,13 +39,8 @@ public String execute(TaskList taskList, Ui ui, FileStorage fileStorage) throws
         Result result = getResult();
         int[] reversedValues = result.reversedValues;
         int[] values = result.values;
-        for (int i = 0; i < reversedValues.length; i++) {
-            for (int j = i + 1; j < reversedValues.length; j++) {
-                if (reversedValues[i] == reversedValues[j]) {
-                    throw new DukeException("Oh no, do not repeat the indexes");
-                }
-            }
-        }
+        checkForDuplicates(reversedValues);
+        checkForDuplicates(values);
         if (commandType.equals("del")) {
             for (int reversedValue : reversedValues) {
                 Task task = taskList.deleteTask(reversedValue - 1);
@@ -68,6 +63,22 @@ public String execute(TaskList taskList, Ui ui, FileStorage fileStorage) throws
         return ui.showNewList(result.newList, taskList, commandType);
     }
 
+    /**
+     * Throws an error if there is a duplicate in the list.
+     *
+     * @param intArray The Int array that will be checked.
+     * @throws DukeException If there are duplicates.
+     */
+    private static void checkForDuplicates(int[] intArray) throws DukeException {
+        for (int i = 0; i < intArray.length; i++) {
+            for (int j = i + 1; j < intArray.length; j++) {
+                if (intArray[i] == intArray[j]) {
+                    throw new DukeException("Oh no, do not repeat the indexes");
+                }
+            }
+        }
+    }
+
     /**
      * Reverses the array of indexes.
      *
diff --git a/src/main/java/duke/Main.java b/src/main/java/duke/Main.java
index c0e3faaf2b..3b45094d4d 100644
--- a/src/main/java/duke/Main.java
+++ b/src/main/java/duke/Main.java
@@ -13,7 +13,7 @@
  */
 public class Main extends Application {
 
-    private Duke duke = new Duke("Testing.txt");
+    private final Duke duke = new Duke("Testing.txt");
 
     @Override
     public void start(Stage stage) {
diff --git a/src/main/java/tasks/Task.java b/src/main/java/tasks/Task.java
index c0028e20cb..c2fc5024e3 100644
--- a/src/main/java/tasks/Task.java
+++ b/src/main/java/tasks/Task.java
@@ -20,7 +20,9 @@ public Task(String name) {
     public Task() {
         this.isEmpty = true;
     }
-    public boolean isItEmpty() { return isEmpty; }
+    public boolean isItEmpty() {
+        return isEmpty;
+    }
     public void setType(String type) {
         this.type = type;
     }