线程通信之生产者消费者传统版、阻塞队列版

一、传统版

代码案例：

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

class ShareData // 资源类
{
    private int number = 0;
    private Lock lock = new ReentrantLock();
    private Condition condition = lock.newCondition();

    public void increment() throws Exception{
        lock.lock();
        try {
            // 1判断
            while (number != 0){
                // 等待，不能生产
                condition.await();
            }
            // 2干活
            number++;
            System.out.println(Thread.currentThread().getName()+"\t"+number);
            // 3通知唤醒
            condition.signalAll();
        } catch (Exception e){
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void decrement() throws Exception{
        lock.lock();
        try {
            // 1判断
            while (number == 0){
                // 等待，不能消费
                condition.await();
            }
            // 2干活
            number--;
            System.out.println(Thread.currentThread().getName()+"\t"+number);
            // 3通知唤醒
            condition.signalAll();
        } catch (Exception e){
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}

/**
 * 一个初始值为0的变量，两个线程对其进行交替操作，一个加1一个减1，来5轮
 *
 * 1 线程  操作  资源类
 * 2 判断  干活  通知
 * 3 防止虚假唤醒机制
 */
public class ProdConsumer_TraditionDemo {

    public static void main(String[] args) {
        ShareData shareData = new ShareData();

        new Thread(()->{
            for (int i = 1; i <= 5; i++){
                try {
                    shareData.increment();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        },"AAA").start();

        new Thread(()->{
            for (int i = 1; i <= 5; i++){
                try {
                    shareData.decrement();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        },"BBB").start();
    }
}

AAA    1
BBB    0
AAA    1
BBB    0
AAA    1
BBB    0
AAA    1
BBB    0
AAA    1
BBB    0

多线程的判断必须使用while，不能使用if。

二、阻塞队列版

代码案例：

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

class MyResource{
    private volatile boolean FLAG = true; // 默认开启，进行生产+消费
    private AtomicInteger atomicInteger = new AtomicInteger();

    BlockingQueue blockingQueue = null;
    public MyResource(BlockingQueue blockingQueue){
        this.blockingQueue = blockingQueue;
        System.out.println(blockingQueue.getClass().getName());
    }

    public void myProd()throws Exception{
        String data = null;
        boolean retValue;

        while(FLAG){
            data = atomicInteger.incrementAndGet()+"";
            retValue = blockingQueue.offer(data, 2L, TimeUnit.SECONDS);
            if(retValue){
                System.out.println(Thread.currentThread().getName()+"\t 插入队列" + data + "成功");
            }else{
                System.out.println(Thread.currentThread().getName()+"\t 插入队列" + data + "失败");
            }
            TimeUnit.SECONDS.sleep(1);
        }
        System.out.println(Thread.currentThread().getName()+"\t大老板叫停了，表示FLAG=false，生产动作结束");
    }

    public void myConsumer()throws Exception{
        String result = null;
        boolean retValue;

        while(FLAG){

            result = blockingQueue.poll(2L, TimeUnit.SECONDS);
            if(null == result || result.equals("")){
                FLAG = false;
                System.out.println(Thread.currentThread().getName()+"\t 超过2秒钟没有取到蛋糕，消费退出");
                System.out.println();
                System.out.println();
                return ;
            }
            System.out.println(Thread.currentThread().getName()+"\t 消费队列" + result + "成功");
        }
    }

    public void stop()throws Exception{
        this.FLAG = false;
    }
}
/**
 * volatile/CAS/atomicInteger/BlockQueue/线程交互/原子引用
 */
public class ProdConsumer_BlockQueueDemo {
    public static void main(String[] args) throws Exception{
        MyResource myResource = new MyResource(new ArrayBlockingQueue<>(10));

        new Thread(()->{
            System.out.println(Thread.currentThread().getName()+"\t 生产线程启动");
            try{
                myResource.myProd();
            }catch (Exception e){
                e.printStackTrace();
            }
        },"Prod").start();

        new Thread(()->{
            System.out.println(Thread.currentThread().getName()+"\t 消费线程启动");
            try{
                myResource.myConsumer();
                System.out.println();
                System.out.println();
            }catch (Exception e){
                e.printStackTrace();
            }
        },"Consumer").start();

        // 暂停一会儿线程
        try { TimeUnit.SECONDS.sleep(5); } catch (InterruptedException e) { e.printStackTrace(); }
        System.out.println();
        System.out.println();
        System.out.println();

        System.out.println("5秒钟时间到，大老板main线程叫停，活动结束");

        myResource.stop();
    }
}

java.util.concurrent.ArrayBlockingQueue
Prod     生产线程启动
Prod     插入队列1成功
Consumer     消费线程启动
Consumer     消费队列1成功
Prod     插入队列2成功
Consumer     消费队列2成功
Prod     插入队列3成功
Consumer     消费队列3成功
Prod     插入队列4成功
Consumer     消费队列4成功
Prod     插入队列5成功
Consumer     消费队列5成功



5秒钟时间到，大老板main线程叫停，活动结束
Prod    大老板叫停了，表示FLAG=false，生产动作结束
Consumer     超过2秒钟没有取到蛋糕，消费退出