How to image shuffle on jlabel?

Question

I am creating a Java desktop application where I want to shuffle image in every 3 sec. I am able to do this, but problem is that I want to use only single JLabel where all image shuffle in every 3 sec and I have code for multiple JLabel

Here is the code I found here. I want to use only single JLabel. How can I achieve this?

/**
 * @see https://stackoverflow.com/a/22423511/230513
 * @see https://stackoverflow.com/a/12228640/230513
 */
public class ImageShuffle extends JPanel {

    private List<Icon> list = new ArrayList<Icon>();
    private List<JLabel> labels = new ArrayList<JLabel>();
    private Timer timer = new Timer(1000, new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            update();
        }
    });

    public ImageShuffle() {
        this.setLayout(new GridLayout(1, 0));
        list.add(UIManager.getIcon("OptionPane.errorIcon"));
        list.add(UIManager.getIcon("OptionPane.informationIcon"));
        list.add(UIManager.getIcon("OptionPane.warningIcon"));
        list.add(UIManager.getIcon("OptionPane.questionIcon"));
        for (Icon icon : list) {
            JLabel label = new JLabel(icon);
            labels.add(label);
            this.add(label);
        }
        timer.start();
    }

    private void update() {
        Collections.shuffle(list);
        int index = 0;
        for (JLabel label : labels) {
            label.setIcon(list.get(index++));
        }
    }

    private void display() {
        JFrame f = new JFrame("ImageShuffle");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

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

            @Override
            public void run() {
                new ImageShuffle().display();
            }
        });
    }
}

Answer 1

This variation of the original example has some unfortunate (but perhaps instructive) problems:

• A new instance of Random is created at each iteration; only one is required.

• The expression r.nextInt(3) + 1 never selects the first or last element of the list.

• The use of numeric literals may cause the program to fail if the size of the list changes.

Instead, shuffle() the list and choose the first element.

private void update() {
    Collections.shuffle(list);
    label.setIcon(list.get(0));
}

As tested:

import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.swing.Icon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;

/**
 * @see https://stackoverflow.com/a/22631012/230513
 * @see https://stackoverflow.com/a/22423511/230513
 * @see https://stackoverflow.com/a/12228640/230513
 */
public class ImageShuffle extends JPanel {

    private List<Icon> list = new ArrayList<Icon>();
    private JLabel label = new JLabel();
    private Timer timer = new Timer(1000, new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            update();
        }
    });

    public ImageShuffle() {
        this.setLayout(new GridLayout(1, 0));
        list.add(UIManager.getIcon("OptionPane.errorIcon"));
        list.add(UIManager.getIcon("OptionPane.informationIcon"));
        list.add(UIManager.getIcon("OptionPane.warningIcon"));
        list.add(UIManager.getIcon("OptionPane.questionIcon"));
        label.setIcon(UIManager.getIcon("OptionPane.informationIcon"));

        timer.start();
    }

    private void update() {
        Collections.shuffle(list);
        label.setIcon(list.get(0));
    }

    private void display() {
        JFrame f = new JFrame("ImageShuffle");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.add(label);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

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

            @Override
            public void run() {
                new ImageShuffle().display();
            }
        });
    }
}