import java.util.Vector;

public class SharedBuffer
{
  public int maxSize = 8;
  public Vector buffer = new Vector( maxSize );
  public int i = 1;

  class Producer extends Thread {
    public void run() {
      while ( true ) {
        produceMessage();
      }
    }
  }

  public synchronized void produceMessage() {
    if ( buffer.size() < maxSize ) {
      buffer.addElement( i );
      System.out.println( "PRODUCER: added item " + i );
      i++;
    }
  }

  class Consumer extends Thread {
    public void run() {
      while ( true ) {
        consumeMessage( this.getId() );
      }
    }
  }

  // this consumeMessage() function needs to be synchronized
  public synchronized void consumeMessage( long threadId ) {
    if ( buffer.size() > 0 ) {
      int n = (Integer)buffer.firstElement();
      buffer.removeElement( n );
      System.out.println( "CONSUMER (thread " + threadId +
                           "): consumed item " + n );
    }
  }

  public void doit() {
    Producer p1 = new Producer();
    Producer p2 = new Producer();
    Consumer c1 = new Consumer();
    Consumer c2 = new Consumer();
    Consumer c3 = new Consumer();

    p1.start();
    p2.start();
    c1.start();
    c2.start();
    c3.start();
  }

  public static void main( String[] args ) {
    SharedBuffer program = new SharedBuffer();
    program.doit();
  }

}