JUC-java.util.concurrent学习（三）---BlockingQueue-优快云博客

本文链接：https://blog.youkuaiyun.com/Actor2/article/details/111404110

该博客是JUC-java.util.concurrent学习的第三部分，主要介绍了BlockingQueue。Queue与List、Set同级，其下有阻塞队列、双端队列、非阻塞队列等。阻塞队列在队列为空取元素或队列满放元素时会阻塞，还提到了四组API及SynchronousQueue。

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JUC-java.util.concurrent学习（三）

BlockingQueue

Queue和List，Set是同一级的，Queue下面有阻塞队列 BlockingQueue，双端队列BlockingDeque，非阻塞队列AbstractQueue

阻塞：在队列为空拿去的时候会阻塞，在队列满了往里面放的时候会阻塞

四组API

操作	抛出异常	有返回值,不抛出异常	阻塞等待	超时等待
添加	add	offer	put	offer
移除	remove	poll	take	poll
判断首	element	peek

/**
 * 抛出异常
 */
public static void test1(){
    ArrayBlockingQueue blockingQueue = new ArrayBlockingQueue<>(3);
    //返回true或者false
    System.out.println(blockingQueue.add("1"));
    System.out.println(blockingQueue.add("2"));
    System.out.println(blockingQueue.add("3"));
    //java.lang.IllegalStateException: Queue full
    //System.out.println(blockingQueue.add("3"));

    //判断首位
    System.out.println(blockingQueue.element());
    
    System.out.println("-----------");

    //qu去除的对象
    System.out.println(blockingQueue.remove());
    System.out.println(blockingQueue.remove());
    System.out.println(blockingQueue.remove());
    //java.util.NoSuchElementException
    //System.out.println(blockingQueue.remove());
}

/**
 * 有返回值，不抛出异常
 */
public static void test2(){
    ArrayBlockingQueue blockingQueue = new ArrayBlockingQueue<>(3);

    System.out.println(blockingQueue.offer("1"));
    System.out.println(blockingQueue.offer("2"));
    System.out.println(blockingQueue.offer("3"));
    //false,不抛出异常
    //System.out.println(blockingQueue.offer("4"));

    //判断首位
    System.out.println(blockingQueue.peek());

    System.out.println("-----------");

    System.out.println(blockingQueue.poll());
    System.out.println(blockingQueue.poll());
    System.out.println(blockingQueue.poll());
    //返回null
    //System.out.println(blockingQueue.poll());
}

/**
 * 阻塞等待
 */
public static void test3() throws InterruptedException {
    ArrayBlockingQueue blockingQueue = new ArrayBlockingQueue<>(3);

    blockingQueue.put("1");
    blockingQueue.put("2");
    blockingQueue.put("3");
    //blockingQueue.put("1");//一直等待



    //判断首位
    System.out.println(blockingQueue.peek());

    System.out.println("-----------");

    System.out.println(blockingQueue.take());
    System.out.println(blockingQueue.take());
    System.out.println(blockingQueue.take());
    //System.out.println(blockingQueue.take());//一直等待
}

/**
 * 超时等待
 */
public static void test4() throws InterruptedException {
    ArrayBlockingQueue blockingQueue = new ArrayBlockingQueue<>(3);

    System.out.println(blockingQueue.offer("1"));
    System.out.println(blockingQueue.offer("2"));
    System.out.println(blockingQueue.offer("3"));
    //超时等待
    System.out.println(blockingQueue.offer("4",2, TimeUnit.SECONDS));

    //判断首位
    System.out.println(blockingQueue.peek());

    System.out.println("-----------");

    System.out.println(blockingQueue.poll());
    System.out.println(blockingQueue.poll());
    System.out.println(blockingQueue.poll());
    //超时等待
    System.out.println(blockingQueue.poll(2,TimeUnit.SECONDS));
}

SynchronousQueue

/**
 * SynchronousQueue同步队列，不存储元素
 * 放入一个值就必须要取出一个值
 */
public class synchronizedQueueDemo {
    public static void main(String[] args) {
        BlockingQueue<String> blockingQueue = new SynchronousQueue<String>();

        new Thread(()->{
            try {
                System.out.println(Thread.currentThread().getName()+"放入了第一个");
                blockingQueue.put("1");
                System.out.println(Thread.currentThread().getName()+"放入了第二个");
                blockingQueue.put("2");
                System.out.println(Thread.currentThread().getName()+"放入了第三个");
                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());
                System.out.println(Thread.currentThread().getName()+"->"+blockingQueue.take());
                System.out.println(Thread.currentThread().getName()+"->"+blockingQueue.take());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"T2").start();
    }
}