Simple Java To-Do App with Core Features (Add/Delete/Mark Complete)

Create a To-Do List App with Add/Delete/Complete Features in Java

Managing tasks is a daily routine for many of us, and a to-do list app helps us stay organized. In this step-by-step tutorial, we will create a To-Do List App in Java using Swing — a GUI toolkit for building desktop apps.

This beginner project will help you understand:

GUI design using Swing
List data management
Event handling (buttons and actions)

Let’s get started!

🧱 Tools & Prerequisites

JDK (Java Development Kit) installed
Any IDE like IntelliJ IDEA, Eclipse, or NetBeans
Basic knowledge of Java syntax and OOP

🎯 Features of Our To-Do List App

Add new tasks
Delete selected tasks
Mark tasks as completed
View tasks in a scrollable list

🧑‍💻 Step-by-Step Code with Explanation

📂 Step 1: Create the Java Class

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;

public class ToDoListApp extends JFrame {
    private DefaultListModel<String> listModel;
    private JList<String> taskList;
    private JTextField taskInput;
    private ArrayList<Boolean> taskCompletionStatus;

    public ToDoListApp() {
        setTitle("To-Do List App");
        setSize(400, 500);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        listModel = new DefaultListModel<>();
        taskList = new JList<>(listModel);
        taskList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        JScrollPane scrollPane = new JScrollPane(taskList);

        taskInput = new JTextField();
        JButton addButton = new JButton("Add Task");
        JButton deleteButton = new JButton("Delete Task");
        JButton completeButton = new JButton("Mark as Complete");

        taskCompletionStatus = new ArrayList<>();

        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(1, 3));
        panel.add(addButton);
        panel.add(deleteButton);
        panel.add(completeButton);

        add(taskInput, BorderLayout.NORTH);
        add(scrollPane, BorderLayout.CENTER);
        add(panel, BorderLayout.SOUTH);

        // Action to add a task
        addButton.addActionListener(e -> {
            String task = taskInput.getText().trim();
            if (!task.isEmpty()) {
                listModel.addElement(task);
                taskCompletionStatus.add(false);
                taskInput.setText("");
            }
        });

        // Action to delete a task
        deleteButton.addActionListener(e -> {
            int selectedIndex = taskList.getSelectedIndex();
            if (selectedIndex != -1) {
                listModel.remove(selectedIndex);
                taskCompletionStatus.remove(selectedIndex);
            }
        });

        // Action to mark as complete
        completeButton.addActionListener(e -> {
            int selectedIndex = taskList.getSelectedIndex();
            if (selectedIndex != -1) {
                boolean isCompleted = taskCompletionStatus.get(selectedIndex);
                if (!isCompleted) {
                    String task = listModel.getElementAt(selectedIndex);
                    task = "✔️ " + task;
                    listModel.set(selectedIndex, task);
                    taskCompletionStatus.set(selectedIndex, true);
                }
            }
        });

        setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(ToDoListApp::new);
    }
}

🔍 Step-by-Step Explanation

1. Imports

2. Class Declaration

We extend JFrame to create a windowed app.

3. UI Components

DefaultListModel<String>: Holds the list of tasks.
JList<String>: Displays the list to users.
JTextField: For inputting new tasks.
JButtons: To add, delete, and mark tasks.

4. Layout & Panels

We use BorderLayout for the main window and GridLayout for the buttons.

5. Add Task Action

When the user enters a task and clicks "Add", we:

Add it to the listModel
Mark its completion as false
Clear the input field

6. Delete Task Action

We delete the selected task from both the list and the status array.

7. Mark Task as Complete

We prepend a checkmark (✔️) to completed tasks and mark them as true.

🧪 Output Preview

When you run the program:

A window opens with a text field and three buttons.
You can enter tasks, select them, and either delete or mark them as complete.

✅ Final Thoughts

This simple To-Do List App in Java is a great project for beginners to:

Practice Java Swing
Understand event-driven programming
Learn how to manipulate lists dynamically

You can further enhance this app by:

Saving tasks to a file
Adding deadlines or categories
Creating a dark/light theme

TOPICS MENTIONED IN THIS ARTICLE

Java to-do app

Java project tutorial

Java Swing to-do list

beginner Java projects

Java task manager app