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public class BlockingQueue {

  private List queue = new LinkedList();
  private int  limit = 10;

  public BlockingQueue(int limit){
    this.limit = limit;
  }


  public synchronized void enqueue(Object item)
  throws InterruptedException  {
 
    while(this.queue.size() == this.limit) {
      wait();
    }
  //Notify all the threads that are waiting 
    if(this.queue.size() == 0) {
      notifyAll();
    }
    this.queue.add(item);
  }


  public synchronized Object dequeue()
  throws InterruptedException{
    while(this.queue.size() == 0){
      wait();
    }
  
    if(this.queue.size() == this.limit){
      notifyAll();
    }

    return this.queue.remove(0);
  }

}

public class MyBlockingQueue<T> {
    
    private Queue<T> queue;
    private AtomicInteger limit = new AtomicInteger(10);
    private Lock put_lock = new ReentrantLock();
    private Lock take_lock = new ReentrantLock();
    
    public MyBlockingQueue(AtomicInteger limit){
        queue = new LinkedList<T>();
        this.limit = limit;
    }
    
    public boolean put(T item) throws InterruptedException{
        put_lock.lockInterruptibly();
        try{
            while(queue.size() == limit.get()){
                put_lock.newCondition().await();
            }
            put_lock.newCondition().signal();
            queue.add(item);
        }finally{
            put_lock.unlock();
        }
        
        return true;
    }
    
    public T take() throws InterruptedException{
        take_lock.lockInterruptibly();
        try{
            while(queue.size() == 0){
                take_lock.newCondition().await();
            }
            take_lock.newCondition().signal();
            return queue.poll();
        }finally {
            take_lock.unlock();
        }
    }
}

I found some comment for this at tutorials.jenkov.com/java-concurrency/blocking-queues.html: "If the queue size is not equal to either bound when enqueue() or dequeue() is called, there can be no threads waiting to either enqueue or dequeue items.

Could anyone elaborate this comment?