Watcher.java Source code

Introduction

Here is the source code for Watcher.java

Source

/*
 * Output: 
    
update() called, count is 10
update() called, count is 9
update() called, count is 8
update() called, count is 7
update() called, count is 6
update() called, count is 5
update() called, count is 4
update() called, count is 3
update() called, count is 2
update() called, count is 1
update() called, count is 0
 *  
 */

import java.util.Observable;
import java.util.Observer;

class Watcher implements Observer {
    public void update(Observable obj, Object arg) {
        System.out.println("update() called, count is " + ((Integer) arg).intValue());
    }
}

class BeingWatched extends Observable {
    void counter(int period) {
        for (; period >= 0; period--) {
            setChanged();
            notifyObservers(new Integer(period));
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                System.out.println("Sleep interrupted");
            }
        }
    }
}

public class MainClass {
    public static void main(String args[]) {
        BeingWatched observed = new BeingWatched();
        Watcher observing = new Watcher();

        observed.addObserver(observing);

        observed.counter(10);
    }
}