Waiting on a condition in a reentrant lock

Question

The following code is taken from the JavaDoc of Condition:

class BoundedBuffer {
  final Lock lock = new ReentrantLock();
  final Condition notFull  = lock.newCo         


        

Answer 1

I tested below code with single monitor and below always performs better - Tested on 2 core machine, Condition performance is 10-15% below on an average

 final Object sync = new Object();
  AtomicInteger add=new AtomicInteger();
  AtomicInteger remove=new AtomicInteger();
   final Object[] items = new Object[1];
   int putptr, takeptr, count;        

 public void add(Object x) throws InterruptedException {
       add.incrementAndGet();

     synchronized (sync) {

       while (count == items.length)
         sync.wait();
       items[putptr] = x;
       if (++putptr == items.length) putptr = 0;
       ++count;
       sync.notify();
        }
   }

   public Object remove() throws InterruptedException {
       remove.incrementAndGet();

     synchronized (sync) {

       while (count == 0)
         sync.wait();
       Object x = items[takeptr];
       if (++takeptr == items.length) takeptr = 0;
       --count;
       sync.notify();
       return x;

       }
   }


  public static void main(String[] args) {
    final BoundedBuffer bf=new BoundedBuffer();

    Thread put =new Thread(){
        public void run(){
        try {
            while(true)
            bf.add(new Object());
        } catch (InterruptedException e) {

        }
        }

    };
    put.start();

    Thread take= new Thread(){
        public void run(){
        try {
        while(true)
            bf.remove();
        } catch (InterruptedException e) {

        }
        }

    };
    take.start();

    try {
        Thread.sleep(1000L);
        put.interrupt();
        take.interrupt();
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


    System.out.println("add:"+bf.add);
    System.out.println("remove:"+bf.remove);