Swings example in java

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;


public class QuitButtonExample extends JFrame {

    public QuitButtonExample() {
       
        initUI();
    }

    private void initUI() {

       JPanel panel = new JPanel();
       getContentPane().add(panel);

       panel.setLayout(null);

       JButton quitButton = new JButton("Quit");
       quitButton.setBounds(50, 60, 80, 30);
      
       quitButton.addActionListener(new ActionListener() {
           @Override
           public void actionPerformed(ActionEvent event) {
               System.exit(0);
          }
       });

       panel.add(quitButton);

       setTitle("Quit button");
       setSize(300, 200);
       setLocationRelativeTo(null);
       setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
       
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                QuitButtonExample ex = new QuitButtonExample();
                ex.setVisible(true);
            }
        });
    }
}