notify() 而不是 notifyAll() 用于阻塞队列

I am trying to find out whether it is possible to have a multiple producer / multiple consumer queue where I can use notify() instead of notifyAll(). For example, in the implementation below (source: here) you cannot just simply switch the notifyAll() for notify(). It is not totally obvious why you cannot switch so I will leave it as an teaser to whoever wants to help me out understanding this problem.

所以下面的代码坏了:

public class BlockingQueue {

  private Object lock = new Object();

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

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


  public void enqueue(Object item)
  throws InterruptedException  {
   synchronized(lock) {
    while(this.queue.size() == this.limit) {
      lock.wait();
    }
    if(this.queue.size() == 0) {
      lock.notify();
    }
    this.queue.add(item);
   }
  }


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

    return this.queue.remove(0);
  }
 }
}

推荐答案

以下步骤导致我们陷入僵局.让我们将 limit 设置为 1 以保持示例简短.