阻塞队列中take方法和poll方法的区别

今天用ArrayBlockingQueue写了一个简单的消费者和生产者模型，代码如下

public class Client {

    private ArrayBlockingQueue<Integer> queue = new ArrayBlockingQueue<>(10,true);

    public static void main(String[] args) throws Exception {
        Client client = new Client();
        Producer producer = client.new Producer();
        Consumer consumer = client.new Consumer();
        producer.start();
        consumer.start();

    }

    class Producer extends Thread{
        @Override
        public void run() {
            super.run();
            for (int i = 0; i < 100; i++) {
                try {
                    queue.put(i);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("producer:"+i);
            }
        }
    }

    class Consumer extends Thread{
        @Override
        public void run() {
            super.run();
            for (int i = 0; i < 100; i++) {
                 int t = queue.poll();
                 System.out.println("consumer:"+t);
            }
        }
    }
}

运行时结果却不是我们想要的，消费者输出了很多的null，将poll()方法改为take()方法后，实现了正确输出，那这两个方法有什么区别呢？看看源码

    public E poll() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return (count == 0) ? null : dequeue();
        } finally {
            lock.unlock();
        }
    }
    public E take() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            while (count == 0)
                notEmpty.await();
            return dequeue();
        } finally {
            lock.unlock();
        }
    }

从源码中可以看出，当队列为null的时候，poll()方法会直接返回null, 不会抛出异常，但是take()方法会一直等待，因此会抛出一个InterruptedException类型的异常。因此我们实现生产者消费者的时候只能用taker（）方法。