Bounded buffer

Question

hi i have created a bounded buffer class called,Q, and this operates as a fixed length first-in-first-out queue of size N. I have two public methods put, which takes an Object as its only parameter, and adds this object to the end of the queue, and get, which removes an object from the front of the queue and returns it as its result.
I have used private Semaphore variables to ensure that any thread attempting to get from an empty buffer, or to put into a full buffer is caused to wait.
Now I have this i want to be able to create two thread, producer and consumer. I want to Write a producer thread which continuously generates objects, and places them in my buffer (Object[] buf), and a consumer thread which takes objects out of the same buffer, I don't know how to create this. Your help would be amazing
The class Semaphore and Q are as follows.
Q class
protected Object[] buf;
protected int in = 0;
protected int out= 0;
protected int size;
private Semaphores full;
private Semaphores empty;
public Q(int size)
this.size = size;
// makes the Object array size (size)
buf = new Object[size];
// creates a new Semaphores saying full is zero
full = new Semaphores(0);
// creates new semaphore saying empty is size(size)
empty = new Semaphores(size);
public void put(Object o) throws InterruptedException
empty.semWait();
synchronized(this)
buf[in] = o;
in=(in+1) % size;
full.semSignal();
System.out.println("put");
public Object get() throws InterruptedException
full.semWait();
Object o;
synchronized(this)
o = buf[out];
buf[out]=null;
out=(out+1) % size;
empty.semSignal();
System.out.println("Get");
return (o);
public class Semaphores implements Semaphore
private int value;
public Semaphores(int value)
this.value = value;
public void semWait()
try
value--;
if( value < 0)
wait();
catch(InterruptedException e)
public void semSignal()
value++;
if( value <= 0)
notify();
}

Answer 1

didn't test the example, but it should work... anyway it's pretty easy to understand.
public class Producer
extends Thread
private Q buffer;
private int cnt;
public Producer(Q buffer, int cnt)
this.buffer = buffer;
this.cnt = cnt;
public Long currentTime()
return new Long(System.currentTime());
public void run()
try
for(int i = 0; i < cnt; i++)
Q.put(currentTime);
Q.put(null);
catch(Exception e)
e.printStackTrace();
public class Consumer
extends Thread
private Q buffer;
public Consumer(Q buffer)
this.buffer = buffer;
public void run()
try
Object o;
while((o = Q.get()) != null)
System.out.println(o);
catch(Exception e)
e.printStackTrace();
public class Test
public static void main(String[] args)
Q buffer = new Q(30);
Producer p = new Producer(buffer,100);
Consumer c = new Consumer(buffer);
p.start();
c.start();
}