OnJava8-Examples/ui/ColorBoxes.java

// ui/ColorBoxes.java
// (c)2016 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
// A visual demonstration of threading.
import javax.swing.*;
import java.awt.*;
import java.util.concurrent.*;
import java.util.*;
import static onjava.SwingConsole.*;

class CBox extends JPanel implements Runnable {
  private int pause;
  private static Random rand = new Random();
  private Color color = new Color(0);
  public void paintComponent(Graphics g) {
    g.setColor(color);
    Dimension s = getSize();
    g.fillRect(0, 0, s.width, s.height);
  }
  public CBox(int pause) { this.pause = pause; }
  public void run() {
    try {
      while(!Thread.interrupted()) {
        color = new Color(rand.nextInt(0x1000000));
        repaint(); // Asynchronously request a paint()
        TimeUnit.MILLISECONDS.sleep(pause);
      }
    } catch(InterruptedException e) {
      // Acceptable way to exit
    }
  }
}

public class ColorBoxes extends JFrame {
  private int grid = 12;
  private int pause = 50;
  private static ExecutorService exec =
    Executors.newCachedThreadPool();
  public void setUp() {
    setLayout(new GridLayout(grid, grid));
    for(int i = 0; i < grid * grid; i++) {
      CBox cb = new CBox(pause);
      add(cb);
      exec.execute(cb);
    }
  }
  public static void main(String[] args) {
    ColorBoxes boxes = new ColorBoxes();
    if(args.length > 0)
      boxes.grid = new Integer(args[0]);
    if(args.length > 1)
      boxes.pause = new Integer(args[1]);
    boxes.setUp();
    run(boxes, 500, 400);
  }
}