Buffer Example help.

[bert682]

Hey guys,
Been given this program that was incomplete, I was to add in the missing parts. The idea is that there is a buffer and a producer adding to it and a consumer removing from it. Code is attached below, bits that I have added are in RED.

import java.io.*;

public class BoundedBuffer 
{
    public static void main(String args[]) 
    {

        // create buffer
        Buffer b = new BufferImpl();
      
       // create producer and consumer threads sharing buffer
[COLOR="Red"]       Consumer c = new Consumer(b);
       Producer p = new Producer(b);[/COLOR]

        //launch producer and consumer threads
[COLOR="Red"]       c.start();
       p.start();[/COLOR]

       try{ Thread.sleep(20000);}
       catch(InterruptedException e){System.exit(0);}

       p.interrupt();
       c.interrupt();

       System.out.println("system timed out");
        
    }

}

public interface Buffer 
{
    public void put(Object obj)
       throws InterruptedException;		//put object into buffer
	
    public Object get()
       throws InterruptedException;     //get an object from buffer
}

public class BufferImpl implements Buffer {

    private Object[] buf;       //the buffer,declared as an array of objects
    private int in = 0;         //index of the next place where an item 
                                //can be added
    private int out= 0;         //index of the next item that can be removed
    private int count= 0;       //count of the number of items in the buffer
    private int size = 5;       //number of slots in the buffer

    public BufferImpl() {
        buf = new Object[5];        //actual buffer can hold 5 objects
    }

    public synchronized void put(Object obj) throws InterruptedException {
      // implement conditional synchronization

      // wait if buffer is full
      [COLOR="Red"]while(buf.length>4){
        	wait();
        }
      
       obj = buf[in];                  //place object into buffer at index 'in'
       count++;                  //increment count of number of items 
                          	//in buffer
       in++;              //increment index 'in'
                         //update of shared data completed[/COLOR]
    }

    public synchronized Object get() throws InterruptedException {
        //implement conditional synchronization

        // wait if buffer is empty
[COLOR="Red"]        while(buf == null){
        	wait();
        }
      [/COLOR]
        Object obj = buf[out];      //get object from buffer at index 'out'
        buf[out] = null;
        size = size - 1;            //decrement number of items in buffer
        out = (out+1) % size;       //increment index 'out'
                                   //update of shared data completed
        return (obj);
    }
}

class Consumer extends Thread 
{
    private Buffer buf;
    private int r = 0;

    Consumer(Buffer b) {buf = b;}

    public void run() {
      try {
        while(true) {
            r = ((Integer)buf.get()).intValue();
		for (int i = 0; i < 5000000; i++) {r=r*2/2;}
		System.out.println("Consume " + r);
        }
      } catch(InterruptedException e ){System.out.println("received interrupt");}
    }
}

public class Producer extends Thread
{
    Buffer buf;		// the buffer used by the producer
    private int r = 2;	// the variable on which a calculation is made

    Producer(Buffer b) {buf = b;}
	
    public void run() {
      try {
          while(true) 
		  {
			r++;			// increment the value of r
			for (int j = 0; j < 2000000; j++) { r = r*2/2;}
			Integer i = new Integer(r);	// create a wrapper object for r
			System.out.println("Produce " + r);
			[COLOR="Red"]buf.put(r);[/COLOR]
			   		//place integer object into buffer
          }
      } catch(InterruptedException e ){System.out.println("received interrupt");}
    }
}

Im totally lost and have no idea where to look.

Regards, Robert.