7.阻塞队列

阻塞队列

四组API

方式	抛出异常	有返回值	阻塞 等待	超时等待
添加	add	offer	put	offer(元素，等待时间，等待时间单位)
移除	remove	poll	take	poll(元素，等待时间，等待时间单位)
过去队列首	element	peek

public class Test {
    public static void main(String[] args) throws InterruptedException {
        test4();
    }

    /*
     * 1.抛出异常
     * */
    public static void test1() {
        //队列大小
        BlockingQueue queue = new ArrayBlockingQueue(3);

        //添加
        System.out.println(queue.add("a"));//true
        System.out.println(queue.add("b"));//true
        System.out.println(queue.add("c"));//true
        //System.out.println(queue.add("d"));//IllegalStateException Queue full 队列已满
        System.out.println(queue.element());//a 首元素

        //移除
        System.out.println(queue.remove());//a
        System.out.println(queue.remove());//b
        System.out.println(queue.remove());//c
        System.out.println(queue.remove());//NoSuchElementException 没有元素了
    }

    /*
     * 2.抛出异常
     * */
    public static void test2() {
        //队列大小
        BlockingQueue queue = new ArrayBlockingQueue(3);

        //添加
        System.out.println(queue.offer("a"));//true
        System.out.println(queue.offer("b"));//true
        System.out.println(queue.offer("c"));//true
        System.out.println(queue.offer("d"));//false
        System.out.println(queue.peek());
        //移除
        System.out.println(queue.poll());//a
        System.out.println(queue.poll());//b
        System.out.println(queue.poll());//c
        System.out.println(queue.poll());
    }

    /*
    * 3.阻塞，等待
    * */
    public static void test3() throws InterruptedException {
        BlockingQueue queue = new ArrayBlockingQueue<>(3);

        //添加
        queue.put("a");
        queue.put("b");
        queue.put("c");
        //queue.put("d");//队列没有位置了，一直阻塞，等待

        //移除
        System.out.println(queue.take());
        System.out.println(queue.take());
        System.out.println(queue.take());
        System.out.println(queue.take());//一直阻塞，等待
    }

    /*
    * 4.等待 超时
    * */
    public static void test4() throws InterruptedException {
        BlockingQueue queue=new ArrayBlockingQueue(3);
        System.out.println(queue.offer("a"));
        System.out.println(queue.offer("b"));
        System.out.println(queue.offer("c"));
        System.out.println(queue.offer("d",2, TimeUnit.SECONDS));//等待2秒后退出，false
        System.out.println(queue.poll());
        System.out.println(queue.poll());
        System.out.println(queue.poll());
        System.out.println(queue.poll(2,TimeUnit.SECONDS));//等待2秒后，null

    }
}

SynchronousQueue

/*
* 同步队列
* 和其他BlockingQueue不一样，SynchronousQueue不能存贮元素，
* put一个元素，必须先take一个元素
* */
public class SynchronousQueueTest {
    public static void main(String[] args) throws InterruptedException {
        BlockingQueue<String> queue = new SynchronousQueue<>();
        new Thread(() -> {
            try {
                System.out.println(Thread.currentThread().getName() + " put a");
                queue.put("a");
                System.out.println("queue:"+queue);

                System.out.println(Thread.currentThread().getName() + " put b");
                queue.put("b");

                System.out.println(Thread.currentThread().getName() + " put c");
                queue.put("c");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "t1").start();


        /*new Thread(() -> {
            try {
                TimeUnit.SECONDS.sleep(3);
                System.out.println(Thread.currentThread().getName() + " take " + queue.take());

                TimeUnit.SECONDS.sleep(3);
                System.out.println(Thread.currentThread().getName() + " take " + queue.take());

                TimeUnit.SECONDS.sleep(3);
                System.out.println(Thread.currentThread().getName() + " take " + queue.take());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "t2").start();*/

    }
}