Basic Java Swing, how to exit and dispose of your application/JFrame

Question

What is a good way to dispose of a JFrame with code like this? I want to handle the Window exit and window close.

I know we shouldn't use System.exit();

public class JavaCellularAutomataSquare {

  public static final String TITLE = "Cellular Automata - Squaring Example";

  private int maxWidth = 600;
  private int maxHeight = 600;

  public void launch() {    
    final JFrame frame = new JFrame(TITLE);   
    frame.setLocation(20, 20);    
    frame.setPreferredSize(new Dimension(maxWidth, maxHeight));
    frame.setResizable(false);
    frame.setFocusable(true);

    final JPanel panel = new JPanel();
    panel.setLocation(20, 20);
    panel.setVisible(true);
    panel.setPreferredSize(new Dimension(maxWidth, maxHeight));    
    panel.setFocusable(true);
    panel.setBackground(Color.white);

    // Panel setup, toggle visibility on frame
    frame.add(panel);
    frame.pack();
    frame.setVisible(true);    
  }

}

Answer 1

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

public class ClosingFrame extends JFrame {

    private JMenuBar MenuBar = new JMenuBar();
    private JFrame frame = new JFrame();
    private static final long serialVersionUID = 1L;
    private JMenu File = new JMenu("File");
    private JMenuItem Exit = new JMenuItem("Exit");

    public ClosingFrame() {
        File.add(Exit);
        MenuBar.add(File);
        Exit.addActionListener(new ExitListener());
        WindowListener exitListener = new WindowAdapter() {

            @Override
            public void windowClosing(WindowEvent e) {
                int confirm = JOptionPane.showOptionDialog(frame,
                        "Are You Sure to Close this Application?",
                        "Exit Confirmation", JOptionPane.YES_NO_OPTION,
                        JOptionPane.QUESTION_MESSAGE, null, null, null);
                if (confirm == JOptionPane.YES_OPTION) {
                    System.exit(0);
                }
            }
        };
        frame.addWindowListener(exitListener);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.setJMenuBar(MenuBar);
        frame.setPreferredSize(new Dimension(400, 300));
        frame.setLocation(100, 100);
        frame.pack();
        frame.setVisible(true);
    }

    private class ExitListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            int confirm = JOptionPane.showOptionDialog(frame,
                    "Are You Sure to Close this Application?",
                    "Exit Confirmation", JOptionPane.YES_NO_OPTION,
                    JOptionPane.QUESTION_MESSAGE, null, null, null);
            if (confirm == JOptionPane.YES_OPTION) {
                System.exit(0);
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                ClosingFrame cf = new ClosingFrame();
            }
        });
    }
}

Answer 2

JFrame.setDefaultCloseOperation(DISPOSE_ON_CLOSE) frees up resources when the window is closed. You can see some of the other operations in the Java tutorials here.

The possible arguments that you can use in the method are defined in the WindowConstants interface, if you are curious about your options.

Answer 3

If you need to perform some operations while closing your application, propably you need a shut down hook . Have a look at this post .

Answer 4

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JFrame.setDefaultCloseOperation(int operation)

JFrame.EXIT_ON_CLOSE