import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;
import javax.swing.tree.*;
import java.applet.*;
import java.util.*;



interface MyObservable
{
      public void addObserver( Object obj );
      public void tellObservers();
    //public void removeObserver( Object obj );
}

interface MyObserver
{
    public void notify( Object obj );
}

class A implements MyObserver
{
      public void notify( Object obj )
      {
	 System.out.println( "A: " + this + " o: " + obj );
      }
}

class B implements MyObservable
{
      Vector collectionOfVariablesForA = new Vector();
      
      Vector observers = new Vector();
      
      public B()
      {
	 collectionOfVariablesForA.addElement( "first" );
	 collectionOfVariablesForA.addElement( new Date() );
	 collectionOfVariablesForA.addElement( new Double( 123.45 ) );
      }
      
      public void addObserver( Object obj )
      {
	 observers.addElement( obj );
      }
      public void tellObservers()
      {
	 for( int i = 0, ii = observers.size(); i < ii; i++ ) 
	 {
	    MyObserver ob = (MyObserver) observers.elementAt( i );
	    ob.notify( collectionOfVariablesForA );
	 }
      }
      public void doSomethingAndTellEveryone() 
      {
	 System.out.println( "B doing something tell everyone: " + this );
	 tellObservers();
      }
}

public class Obs
{
      private void initialize()
      {
	 B b = new B();
	 A a = new A();
	 A aa = new A();
	 b.addObserver( a );
	 b.addObserver( aa );
	 b.doSomethingAndTellEveryone();
      }
      public static void main( String[] args ) 
      {
	 Obs obs = new Obs();
	 obs.initialize();
      }
}