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Question:

I am new in Java Form Application development using Swing. What is the suitable code for exit button that will exit the application?

For example:In C# (.NET Framework) we use Application.Exit(); as the code for exit what button. What is the equivalent code in Java to exit an application?


Best Answer:


@AndrewThompson is right about JFrame.EXIT_ON_CLOSE but you can take steps to avoid just killing stuff.

JFrame.EXIT_ON_CLOSE is just fine, if you handle cleanup in an overridden JFrame.processWindowEvent(WindowEvent) checking for WindowEvent.WINDOW_CLOSING events.

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JProgressBar;
import javax.swing.Timer;
public class ExitJFrame extends JFrame {
    public ExitJFrame() {
        setLayout(new BorderLayout());
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JButton button = new JButton("Exit");
        add(button);
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                ExitJFrame.this.processWindowEvent(
                        new WindowEvent(
                                ExitJFrame.this, WindowEvent.WINDOW_CLOSING));
            }
        });
        setSize(200, 200);
        setLocationRelativeTo(null);
    }
    @Override
    protected void processWindowEvent(WindowEvent e) {
        // more powerful as a WindowListener, since you can consume the event 
        // if you so please - asking the user if she really wants to exit for
        // example, do not delegate to super if consuming.
        if (e.getID() == WindowEvent.WINDOW_CLOSING) {
            doCleanup();
            super.processWindowEvent(e); 
        } else {        
            super.processWindowEvent(e); 
        }
    }
    private void doCleanup() {
        final JDialog dialog = new JDialog(this, true);
        dialog.setLayout(new BorderLayout());
        dialog.setUndecorated(true);
        JProgressBar progress = new JProgressBar();
        dialog.add(progress);
        dialog.add(new JLabel("Waiting for non-daemon threads to exit gracefully..."), BorderLayout.NORTH);
        progress.setIndeterminate(true);
        Timer timer = new Timer(2000, new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                dialog.setVisible(false);
                dialog.dispose();
            }
        });
        timer.setRepeats(false);
        timer.start();
        dialog.pack();
        dialog.setLocationRelativeTo(this);
        dialog.setVisible(true);
    }
    public static void main (String[] args) {
        new ExitJFrame().setVisible(true);
    }
}



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