JUC编程——（三）（ReadWriteLock，BlockingQueue，SynchronousQueue）

1、ReadWriteLock

package com.JUC编程.代码;
import java.util.HashMap;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyReadWriteLock myReadWriteLock = new MyReadWriteLock();
        //读
        for (int i = 1; i <=5; i++) {
            final int temp=i;
            new Thread(()->{
                myReadWriteLock.Write(temp+"",temp+"");
            },String.valueOf(i)).start();
        }
        //写
        for (int i = 1; i <=5; i++) {
            final int temp=i;
            new Thread(()->{
                myReadWriteLock.Read(temp+"");
            },String.valueOf(i)).start();
        }
    }
}
class MyReadWriteLock{
    private volatile HashMap<String,String> hashMap=new HashMap<>();
    ReadWriteLock lock= new ReentrantReadWriteLock();
        public void Write(String s1,String s2){
            lock.writeLock().lock();
            try {
                System.out.println(Thread.currentThread().getName()+"开始写入");
                hashMap.put(s1,s2);
                System.out.println(Thread.currentThread().getName()+"写入完成");
            } catch (Exception e) {
                e.printStackTrace();
            }finally {
                lock.writeLock().unlock();
            }
        }
        public void Read(String key){
            lock.readLock().lock();
            try {
                System.out.println(Thread.currentThread().getName()+"开始读");
                String s = hashMap.get(key);
                System.out.println(Thread.currentThread().getName()+"读完成");
            } catch (Exception e) {
                e.printStackTrace();
            }finally{
                lock.readLock().unlock();
            }
        }
}

2、BlockingQueue

（1）队列

队列的特点：先进后出，对头出，对尾入。
什么时候会发生阻塞?

• 对列已满，但还想再入队列
• 队列为空，想要出队列

（2）阻塞队列的继承关系

（3）使用

四组API

 /*
  * 抛出异常
  * */
public static void test(){
        ArrayBlockingQueue arrayBlockingQueue = new ArrayBlockingQueue<>(3);
        System.out.println(arrayBlockingQueue.add("a"));
        System.out.println(arrayBlockingQueue.add("b"));
        System.out.println(arrayBlockingQueue.add("c"));
        //抛出异常Exception in thread "main" java.lang.IllegalStateException: Queue full
        //arrayBlockingQueue.add("d");
        System.out.println("=======================");
        System.out.println(arrayBlockingQueue.remove());
        System.out.println(arrayBlockingQueue.remove());
        System.out.println(arrayBlockingQueue.remove());
        //抛出异常Exception in thread "main" java.util.NoSuchElementException
        //System.out.println(arrayBlockingQueue.remove());
    }

public static void test1(){
        /*
        * 不抛出异常
        * */
        ArrayBlockingQueue arrayBlockingQueue = new ArrayBlockingQueue<>(3);
        System.out.println(arrayBlockingQueue.offer("a"));
        System.out.println(arrayBlockingQueue.offer("b"));
        System.out.println(arrayBlockingQueue.offer("c"));
        System.out.println(arrayBlockingQueue.offer("d"));//false
        System.out.println(arrayBlockingQueue.poll());
        System.out.println(arrayBlockingQueue.poll());
        System.out.println(arrayBlockingQueue.poll());
        System.out.println(arrayBlockingQueue.poll());//null
    }

public static void test2() throws InterruptedException {
        /*
        * 一直阻塞等待
        * */
        ArrayBlockingQueue arrayBlockingQueue = new ArrayBlockingQueue<>(3);
        arrayBlockingQueue.put("a");
        arrayBlockingQueue.put("b");
        arrayBlockingQueue.put("c");
        //如果队列满 就会一直阻塞
        //arrayBlockingQueue.put("d");
        System.out.println(arrayBlockingQueue.take());
        System.out.println(arrayBlockingQueue.take());
        System.out.println(arrayBlockingQueue.take());
        //队列为空 一直阻塞
        //System.out.println(arrayBlockingQueue.take());
    }

public static void test3() throws InterruptedException {
        /*
        *阻塞等待 超时退出
        * */
        ArrayBlockingQueue arrayBlockingQueue = new ArrayBlockingQueue<>(3);
        arrayBlockingQueue.offer("a");
        arrayBlockingQueue.offer("b");
        arrayBlockingQueue.offer("c");
       // arrayBlockingQueue.offer("d",2, TimeUnit.SECONDS);
        System.out.println(arrayBlockingQueue.poll());
        System.out.println(arrayBlockingQueue.poll());
        System.out.println(arrayBlockingQueue.poll());
        System.out.println(arrayBlockingQueue.poll(2,TimeUnit.SECONDS));
    }

3、SynchronousQueue

package com.JUC编程.代码;
import java.util.concurrent.SynchronousQueue;
public class SynchronousQueueDemo {
    public static void main(String[] args) {
    //SynchronousQueue同步队列可以说没有容量，put了一个元素,必须先take出来
    SynchronousQueue<String> queue = new SynchronousQueue<>();
    new Thread(()->{
        try {
            System.out.println(Thread.currentThread().getName()+" put a");
            queue.put("a");
            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();
        }
    }).start();
    new Thread(()->{
        try {
            System.out.println("take "+queue.take());
            System.out.println("take "+queue.take());
            System.out.println("take "+queue.take());
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }).start();
    }
}