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

public class GUI17 extends JFrame {

    public GUI17() {
        Color tab[] = {
                Color.BLACK,
                Color.GREEN,
                Color.RED,
                Color.MAGENTA
        };
        JPanel jp = new JPanel();
        jp = new JPanel();
        jp.setPreferredSize(new Dimension(400,400));
        jp.setBackground(Color.white);
        JButton jb = new JButton("Colors");
        jb.addActionListener(
                new ActionListener() {
                    int index = 0;
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        if(index == tab.length){
                            index = 0;
                        }
                        jb.setBackground(tab[index]);
                        index++;
                    }
                }
        );
        jp.setLayout(new BorderLayout());
        jp.add(jb,BorderLayout.CENTER);
        this.add(jp);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.pack();
        this.setVisible(true);
        this.setLocationRelativeTo(null);
        this.setTitle("GUI15");
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(
                ()->new GUI17()
        );
    }
}