A-Assertions

* Enable Assertions as it is disabled by default.
* Add assert in TaskList to check index range.

build.gradle

@@ -66,4 +66,5 @@ shadowJar {
 
 run{
     standardInput = System.in
+    enableAssertions = true
 }

data/duke.txt

@@ -1 +1 @@
-T|false|1
+T|true|1

src/main/java/duke/Duke.java

@@ -45,7 +45,6 @@ public static void main(String[] args) {
     public void start(Stage stage) {
         // Read file
         Storage.readTask(tasks, ui);
-
         //Step 1. Setting up required components
 
         //The container for the content of the chat to scroll.

src/main/java/duke/TaskList.java

@@ -36,6 +36,7 @@ public void add(Task task) {
      * @param index The index of the task to be removed.
      */
     public void remove(int index) {
+        assert  index >= 0 : "index should be >= 0";
         tasks.remove(index);
     }
 
@@ -45,6 +46,7 @@ public void remove(int index) {
      * @param index The index of the task to be marked as done.
      */
     public void mark(int index) {
+        assert  index >= 0 : "index should be >= 0";
         tasks.get(index).mark();
     }
 
@@ -54,6 +56,7 @@ public void mark(int index) {
      * @param index The index of the task to be unmarked.
      */
     public void unmark(int index) {
+        assert  index >= 0 : "index should be >= 0";
         tasks.get(index).unmark();
     }
 

src/main/java/duke/command/MarkCommand.java

@@ -3,6 +3,7 @@
 import duke.TaskList;
 import duke.Ui;
 import duke.exception.DukeException;
+import duke.task.Task;
 
 /**
  * Command that marks a specific task.
@@ -22,8 +23,9 @@ public boolean execute(TaskList tasks, Ui ui) throws DukeException {
             String msg = ui.getLastMsg();
             String[] words = msg.toLowerCase().split("\\s+");
             int index = Integer.parseInt(words[1]) - 1;
+            Task task = tasks.get(index);
             tasks.mark(index);
-            ui.respond("Nice! I've marked this task as done: " + "\n" + tasks.get(index));
+            ui.respond("Nice! I've marked this task as done: " + "\n" + task);
         } catch (Exception e) {
             throw new DukeException("Wrong index. Try checking your list first.");
         }

src/main/java/duke/command/UnmarkCommand.java

@@ -3,6 +3,7 @@
 import duke.TaskList;
 import duke.Ui;
 import duke.exception.DukeException;
+import duke.task.Task;
 
 /**
  * Command that un-marks a specific task.
@@ -23,8 +24,9 @@ public boolean execute(TaskList tasks, Ui ui) throws DukeException {
             String msg = ui.getLastMsg();
             String[] words = msg.toLowerCase().split("\\s+");
             int index = Integer.parseInt(words[1]) - 1;
+            Task task = tasks.get(index);
             tasks.unmark(index);
-            ui.respond("OK, I've marked this task as not done yet:" + "\n" + tasks.get(index));
+            ui.respond("OK, I've marked this task as not done yet:" + "\n" + task);
         } catch (Exception e) {
             throw new DukeException("Wrong index. Try checking your list first.");
         }