阻塞队列

BlockingQueue

方式	抛出异常	有返回值,不抛出异常	阻塞等待	超时等待
添加	boolean add(E e)	boolean offer(E e)	void put(E e)	boolean offer(E e, long timeout, TimeUnit unit)
移除	E remove()	E poll()	E take()	E poll(long timeout, TimeUnit unit)
检测队首元素	E element()	E peek()	-	-

    /*
    抛出异常
     */
    public static void test1() {
        // 参数:队列的大小
        ArrayBlockingQueue<Object> blockingQueue = new ArrayBlockingQueue<>(3);

        System.out.println(blockingQueue.add("a"));
        System.out.println(blockingQueue.add("b"));
        System.out.println(blockingQueue.add("c"));

        // java.lang.IllegalStateException: Queue full 抛出异常!
//        System.out.println(blockingQueue.add("d"));

        System.out.println("=========================");
        System.out.println(blockingQueue.remove());
        System.out.println(blockingQueue.element());//查看队首元素是谁
        System.out.println(blockingQueue.remove());
        System.out.println(blockingQueue.remove());

        // java.util.NoSuchElementException
//        System.out.println(blockingQueue.remove());
    }

    /*
    有返回值,没有异常
     */
    public static void test2() {
        // 参数:队列的大小
        ArrayBlockingQueue<Object> blockingQueue = new ArrayBlockingQueue<>(3);

        System.out.println(blockingQueue.offer("a"));
        System.out.println(blockingQueue.offer("b"));
        System.out.println(blockingQueue.offer("c"));

//        System.out.println(blockingQueue.offer("d"));//false 不抛出异常

        System.out.println(blockingQueue.peek());
        System.out.println("===========================");
        System.out.println(blockingQueue.poll());
        System.out.println(blockingQueue.poll());
        System.out.println(blockingQueue.poll());
        System.out.println(blockingQueue.poll());//null 不抛出异常
    }

    /*
    等待,阻塞(一直阻塞)
     */
    public static void test3() throws InterruptedException {
        // 参数:队列的大小
        ArrayBlockingQueue<Object> blockingQueue = new ArrayBlockingQueue<>(3);

        blockingQueue.put("a");
        blockingQueue.put("b");
        blockingQueue.put("c");
//        blockingQueue.put("d");//队列没有位置,一直阻塞
        System.out.println(blockingQueue.take());
        System.out.println(blockingQueue.take());
        System.out.println(blockingQueue.take());
        System.out.println(blockingQueue.take());
    }
    /*
    等待,阻塞(等待超时)
     */
    public static void test4() throws InterruptedException {
        // 参数:队列的大小
        ArrayBlockingQueue<Object> blockingQueue = new ArrayBlockingQueue<>(3);

        blockingQueue.offer("a");
        blockingQueue.offer("b");
        blockingQueue.offer("c");
//        blockingQueue.offer("d",2, TimeUnit.SECONDS);//等待超过两秒就退出

        System.out.println(blockingQueue.poll());
        System.out.println(blockingQueue.poll());
        System.out.println(blockingQueue.poll());
        System.out.println(blockingQueue.poll(2, TimeUnit.SECONDS));//等待超过两秒就退出
    }

SynchronousQueue

/*
同步队列
和其他的BlockingQueue不一样,SynchronousQueue不存储元素
put了一个元素,必须从里面先take取出来,否则不能再put进去取!
 */
public class SynchronousQueueDemo {
    public static void main(String[] args) {
        BlockingQueue<String> blockingQueue = new SynchronousQueue<>();//同步队列

        new Thread(() -> {
            try {
                System.out.println(Thread.currentThread().getName() + " put 1");
                blockingQueue.put("1");
                System.out.println(Thread.currentThread().getName() + " put 2");
                blockingQueue.put("2");
                System.out.println(Thread.currentThread().getName() + " put 3");
                blockingQueue.put("3");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "T1").start();

        new Thread(() -> {
            try {
                TimeUnit.SECONDS.sleep(2);
                System.out.println(Thread.currentThread().getName() + "=>" + blockingQueue.take());
                TimeUnit.SECONDS.sleep(2);
                System.out.println(Thread.currentThread().getName() + "=>" + blockingQueue.take());
                TimeUnit.SECONDS.sleep(2);
                System.out.println(Thread.currentThread().getName() + "=>" + blockingQueue.take());

            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }, "T2").start();
    }
}