问一个 Java 的 Condition 问题

有两个线程，一个生产者，一个消费者，不断的在队列里面插数据和取数据。 有个问题 notFull.signalAll()这句代码一个放在 try 里面，一个放在 finally 里面控制台输出结果为什么不一样？

 public class ConditionDemo2 { private int queueSize = 10; prvate PriorityQueue<Integer> queue = new PriorityQueue<Integer>(queueSize); private Lock lock = new ReentrantLock(); private Condition notFull = lock.newCondition(); private Condition notEmpty = lock.newCondition(); public static void main(String[] args) { ConditionDemo2 conditionDemo2 = new ConditionDemo2(); Producer producer = conditionDemo2.new Producer(); Consumer cOnsumer= conditionDemo2.new Consumer(); producer.start(); consumer.start(); } class Consumer extends Thread { @Override public void run() { consume(); } private void consume() { while (true) { lock.lock(); try { while (queue.size() == 0) { System.out.println("队列空，等待数据"); try { notEmpty.await(); } catch (InterruptedException e) { e.printStackTrace(); } } queue.poll(); notFull.signalAll();//看这里---------------------- System.out.println("从队列里取走了一个数据，队列剩余" + queue.size() + "个元素"); } finally { lock.unlock(); } } } } class Producer extends Thread { @Override public void run() { produce(); } private void produce() { while (true) { lock.lock(); try { while (queue.size() == queueSize) { System.out.println("队列满，等待有空余"); try { notFull.await(); } catch (InterruptedException e) { e.printStackTrace(); } } queue.offer(1); notEmpty.signalAll();//看这里---------------------- System.out.println("向队列插入了一个元素，队列剩余空间" + (queueSize - queue.size())); } finally { lock.unlock(); } } } } } 

 public class ConditionDemo3 { private int queueSize = 10; private PriorityQueue<Integer> queue = new PriorityQueue<Integer>(queueSize); private Lock lock = new ReentrantLock(); private Condition notFull = lock.newCondition(); private Condition notEmpty = lock.newCondition(); public static void main(String[] args) { ConditionDemo3 conditionDemo2 = new ConditionDemo3(); Producer producer = conditionDemo2.new Producer(); Consumer cOnsumer= conditionDemo2.new Consumer(); producer.start(); consumer.start(); } class Consumer extends Thread { @Override public void run() { consume(); } private void consume() { while (true) { lock.lock(); try { while (queue.size() == 0) { System.out.println("队列空，等待数据"); try { notEmpty.await(); } catch (InterruptedException e) { e.printStackTrace(); } } queue.poll(); System.out.println("从队列里取走了一个数据，队列剩余" + queue.size() + "个元素"); } finally { notFull.signalAll();//看这里---------------------- lock.unlock(); } } } } class Producer extends Thread { @Override public void run() { produce(); } private void produce() { while (true) { lock.lock(); try { while (queue.size() == queueSize) { System.out.println("队列满，等待有空余"); try { notFull.await(); } catch (InterruptedException e) { e.printStackTrace(); } } queue.offer(1); System.out.println("向队列插入了一个元素，队列剩余空间" + (queueSize - queue.size())); } finally { System.out.println("final"); notFull.signalAll();//看这里---------------------- lock.unlock(); } } } } }