add more comments

src/main/java/duke/Duke.java

@@ -54,6 +54,9 @@ public void run() {
         }
     }
 
+    /**
+     * Set the filePath and activate run function.
+     */
     public static void main(String[] args) {
         new Duke("./data/tasks.txt").run();
     }

src/main/java/duke/command/ByeCommand.java

@@ -15,6 +15,12 @@ public ByeCommand() {
         isExit = true;
     }
 
+    /**
+     * Execute user's "bye" command and change the storage file accordingly.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();
         System.out.println("     Bye. Hope to see you again soon!");

src/main/java/duke/command/Command.java

@@ -17,12 +17,28 @@ public abstract class Command {
     String keyword;
     String statement;
     Boolean isExit = false;
+
+    /**
+     * Execute a specific user's command and change the storage file accordingly.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public abstract void execute(TaskList taskList, Ui ui, Storage storage);
 
+    /**
+     * Decide if the user wants to quit.
+     */
     public Boolean isExit() {
         return isExit;
     }
 
+    /**
+     * Create a directory "data" if not exists to contain the "tasks.txt".
+     * @param ui dealing with interactions with the user.
+     * @param tasks the task list.
+     * @param storage The storage file of tasks.
+     */
     static void createDirectory(Ui ui, Storage storage, ArrayList<Task> tasks) {
         ui.showLine();
         System.out.println("     Seems the data directory doesn't exist yet. Try to create for you!");

src/main/java/duke/command/DeadlineCommand.java

@@ -15,6 +15,13 @@ public DeadlineCommand(String keyword, String statement) {
         this.keyword = keyword;
         this.statement = statement;
     }
+
+    /**
+     * Execute user's "deadline" command and change the storage file accordingly.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();
         tryAddDeadline(tasks, statement);

src/main/java/duke/command/DeleteCommand.java

@@ -15,6 +15,13 @@ public DeleteCommand(String keyword, String statement) {
         this.keyword = keyword;
         this.statement = statement;
     }
+
+    /**
+     * Execute user's "delete" command and change the storage file accordingly.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();
         tryDeleteTask(tasks, statement);

src/main/java/duke/command/EventCommand.java

@@ -14,6 +14,13 @@ public EventCommand(String keyword, String statement) {
         this.keyword = keyword;
         this.statement = statement;
     }
+
+    /**
+     * Execute user's "event" command and change the storage file accordingly.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();
         tryAddEvent(tasks, statement);

src/main/java/duke/command/FindCommand.java

@@ -17,6 +17,12 @@ public FindCommand(String statement) {
         this.statement = statement;
     }
 
+    /**
+     * Execute user's "find" command.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     @Override
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();

src/main/java/duke/command/ListCommand.java

@@ -15,6 +15,12 @@ public ListCommand(String keyword, String statement) {
         this.statement = statement;
     }
 
+    /**
+     * Execute user's "list" command.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();
         printTaskList(tasks);

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

@@ -16,6 +16,13 @@ public MarkCommand(String keyword, String statement) {
         this.keyword = keyword;
         this.statement = statement;
     }
+
+    /**
+     * Execute user's "mark" command and change the storage file accordingly.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();
         tryMarkTask(tasks, statement);

src/main/java/duke/command/TodoCommand.java

@@ -19,6 +19,13 @@ public TodoCommand(String keyword, String statement) {
         this.keyword = keyword;
         this.statement = statement;
     }
+
+    /**
+     * Execute user's "todoTask" command and change the storage file accordingly.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();
         tryAddTodo(tasks, statement);

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

@@ -15,6 +15,13 @@ public UnmarkCommand(String keyword, String statement) {
         this.keyword = keyword;
         this.statement = statement;
     }
+
+    /**
+     * Execute user's "unmark" command and change the storage file accordingly.
+     * @param taskList The list containing tasks.
+     * @param ui dealing with interactions with the user.
+     * @param storage The storage file of tasks.
+     */
     public void execute(TaskList taskList, Ui ui, Storage storage) {
         ArrayList<Task> tasks = taskList.getTasks();
         tryUnmarkTask(tasks, statement);

src/main/java/duke/exception/DukeException.java

@@ -1,5 +1,9 @@
 package duke.exception;
 
+
+/**
+ * Exceptions specific to Duke.
+ */
 public class DukeException extends Exception{
 }
 

src/main/java/duke/parser/Parser.java

@@ -8,6 +8,11 @@ public class Parser {
 
     private static String keyword;
     private static String statement;
+
+    /**
+     * Parse the user's input into formatted command.
+     * @param fullCommand a single user's command line.
+     */
     public static Command parse(String fullCommand) throws DukeException {
         fullCommand = fullCommand.trim();
         if (countWithSplit(fullCommand) == 0) throw new DukeException();