Implementing Runnable Interface

• The other way to implement a thread is to implement a class that implements the Runnable interface.
• This is very useful when you want your class to extend some other class.
• You must implement the run() method.

import java.awt.Graphics;
import java.awt.Color;
import java.util.*;
import java.text.DateFormat;

public class Clock extends java.applet.Applet implements Runnable {
  private Thread clockThread = null;

  //Applet method
  public void init() {
    setBackground(Color.white);
  }

  //Applet method
  public void start() {
    if (clockThread == null) {
      clockThread = new Thread(this, "Clock");
      clockThread.start(); //thread starts running
    }
  }

  //A Thread method.
  public void run() {
    Thread myThread = Thread.currentThread();
    while (clockThread == myThread) {
      repaint(); //causes paint() to be called
      try {
        Thread.sleep(1000);
      } catch (InterruptedException e){ }
    }
  }

  //An applet method.
  public void paint(Graphics g) {
    Calendar cal = Calendar.getInstance();
    Date date = cal.getTime();
    DateFormat dateFormatter = DateFormat.getTimeInstance();
    g.drawString(dateFormatter.format(date), 5, 10);
  }
  // overrides Applet's stop method, not Thread's
  public void stop() {
    clockThread = null;
  }
}