JUC并发编程--- 阻塞队列和同步队列使用

Posted 2021-07-22 小样5411

前言

主要涉及一些方法，根据开发实际情况，选择用哪个方法

一、阻塞队列

抛出异常
add与remove，设置队列大小为3，已经添加3个再添加就会抛出异常，remove同理，如果队列没有还remove就会抛出异常java.util.NoSuchElementException
但如果我们不要抛出异常呢，就可以用有返回值的，不能添加就返回false，不抛异常

package com.yx.queue;

import java.util.concurrent.ArrayBlockingQueue;

public class BlockingQueue {
    public static void main(String[] args) {
        test1();
        
    }

    private static void test1() {
        //创建一个队列大小为3的队列
        ArrayBlockingQueue blockingQueue = new ArrayBlockingQueue<>(3);
        System.out.println(blockingQueue.add("a"));
        System.out.println(blockingQueue.add("b"));
        System.out.println(blockingQueue.add("c"));
        //System.out.println(blockingQueue.add("d"));//添加第四个就会抛出异常java.lang.IllegalStateException: Queue full

        System.out.println("===========");
        System.out.println(blockingQueue.remove());
        System.out.println(blockingQueue.remove());
        System.out.println(blockingQueue.remove());
        System.out.println(blockingQueue.remove());//抛出异常java.util.NoSuchElementException


    }

}

有返回值不抛出异常

offer()与poll()

package com.yx.queue;

import java.util.concurrent.ArrayBlockingQueue;

public class BlockingQueue {
    public static void main(String[] args) {
        test2();
        
    }

    private static void test2() {
        //创建一个队列大小为3的队列
        ArrayBlockingQueue 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"));//返回false，不跑出异常，表示添加不成功

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

}

阻塞等待
put()与take()，一直阻塞，程序不停止

private static void test3() throws InterruptedException {
        //创建一个队列大小为3的队列
        ArrayBlockingQueue 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("================");
        System.out.println(blockingQueue.take());
        System.out.println(blockingQueue.take());
        System.out.println(blockingQueue.take());
        System.out.println(blockingQueue.take());
    }

等待，等待超时
offer()，poll()

private static void test4() throws InterruptedException {
        //创建一个队列大小为3的队列
        ArrayBlockingQueue blockingQueue = new ArrayBlockingQueue<>(3);
        blockingQueue.offer("a");
        blockingQueue.offer("b");
        blockingQueue.offer("c");
        blockingQueue.offer("d",2, TimeUnit.SECONDS);//等待两秒就退出
        System.out.println("================");
        System.out.println(blockingQueue.poll());
        System.out.println(blockingQueue.poll());
        System.out.println(blockingQueue.poll());
        blockingQueue.poll(2,TimeUnit.SECONDS);//等待两秒就退出
    }

二、同步队列

SynchronousQueue同步队列
该同步队列没有容量，进去一个元素，必须等待取出之后，才能再往里面放一个元素

package com.yx.queue;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.TimeUnit;

public class SynchronousQueueDemo {
    public static void main(String[] args) {
        BlockingQueue<String> blockingQueue = new SynchronousQueue<>();

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

        new Thread(()->{

            try {
                TimeUnit.SECONDS.sleep(2);
                System.out.println(Thread.currentThread().getName()+"->take->"+blockingQueue.take());
                TimeUnit.SECONDS.sleep(2);
                System.out.println(Thread.currentThread().getName()+"->take->"+blockingQueue.take());
                TimeUnit.SECONDS.sleep(2);
                System.out.println(Thread.currentThread().getName()+"->take->"+blockingQueue.take());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"B").start();
    }
}