Blocking Queue

// Todo

• http://blog.csdn.net/craiglin1992/article/details/44747863

Problem

public interface BlockingQueue
{
    /** Retrieve and remove the head of the queue, waiting if no elements
    are present. */
    T take();

    /** Add the given element to the end of the queue, waiting if necessary
    for space to become available. */
    void put (T obj);
}

Solution

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();
    }
    /** This is what comes from the post, but if you notify here, say a 'dequeue()' is waiting, the size would remain at 0 doesn't it? So I would call notify at the end
    if(this.queue.size() == 0) {
      notifyAll();
    }
    **/
    this.queue.add(item);
    notifyAll();
  }


  public synchronized Object dequeue()
  throws InterruptedException{
    while(this.queue.size() == 0){
      wait();
    }
    /** This is what comes from the post, but if you notify here, say a 'enqueue()' is waiting, the size would remain at the limit doesn't it? So I would call notify at the end

    if(this.queue.size() == this.limit){
      notifyAll();
    }
    **/

    Object ret = this.queue.remove(0);
    notifyAll();
    return ret;

  }

}