// file:    MyObserver.java
// author:  keller
// purpose: Illustrating Observer pattern in Java, 
//          using Java Observable and Observer base classes

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

class Parameters
{
public static int numObservers = 5;
}

class MyObservable extends Observable
{
private int value = 0;

public void setValue(int value)
  {
  this.value = value;
  setChanged();
  notifyObservers("new value = " + value);
  }

public int getValue()
  {
  return value;
  }
}

class MyObserver implements Observer
{
int index;

MyObserver(int index)
  {
  this.index = index;
  }

public void update(Observable observable, Object arg)
  {
  System.out.println("Observed by MyObserver " + index + ": " + arg);
  }

public static void main(String arg[])
  {
  MyObservable observable = new MyObservable();

  for( int i = 0; i < Parameters.numObservers; i++ )
    {
    observable.addObserver(new MyObserver(i));
    }

  observable.setValue(1);
  observable.setValue(2);
  observable.setValue(3);
  }
}