javax.swing.Timer slowdown in Java7u40

Question

Invoke javax.swing.Timer#start() same time,

7u25 is not problem.

Answer 1

Several issues arise in your example:

• Swing GUI objects should be constructed and manipulated only on the event dispatch thread.

• All Swing Timer instances share a common thread, which is being saturated.

Depending on the goal, some alternatives are possible:

• Use a single Timer instance, and select some fraction for update at a proportionally higher rate. The example below randomly selects N of the components and updates them every 100 ms.

• Use TexturePaint, as shown here.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
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 java.util.Random;
import javax.swing.*;

/** @see https://stackoverflow.com/a/18936444/230513 */
public class BlinkenLights {

    private static final int S = 24;
    private static final int N = 10;
    private static final Random r = new Random();
    private static final List list = new ArrayList();

    private static final class MyComponent extends JComponent {

        public MyComponent() {
            this.setOpaque(true);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(S, S);
        }

        @Override
        protected void paintComponent(Graphics g) {
            g.setColor(Color.getHSBColor(r.nextFloat() / 6, 1, 1));
            g.fillRect(0, 0, getWidth(), getHeight());
        }
    }

    private static JPanel createPanel() {
        final JPanel p = new JPanel();
        p.setLayout(new GridLayout(N, N));
        for (int i = 0; i < N * N; i++) {
            MyComponent c = new MyComponent();
            p.add(c);
            list.add(c);
        }
        Timer t = new Timer(1000 / N, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                Collections.shuffle(list, r);
                for (int i = 0; i < N; i++) {
                    list.get(i).repaint();
                }
            }
        });
        t.start();
        return p;
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame f = new JFrame();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.add(createPanel());
                f.pack();
                f.setLocationRelativeTo(null);
                f.setVisible(true);
            }
        });
    }
}