线程通信问题

Posted 2021-03-20 liuyi13535496566

/**
 * 现在两个线程，可以操作初始值为零的一个变量，实现一个线程对该变量加1，一个线程对该变量减1，交替，来10轮。
 * 1    多线程编程工程化模板-上
 *       1.1 线程      操作      资源类
 *       1.2 高内聚 低耦合
 *
 * 2     多线程编程工程化模板-下
 *      2.1 判断
 *      2.2 干活
 *      2.3 通知
 *
 * 3    多线程中的判断问题，也即不要避免：虚假唤醒
 *      用while
 */

class ShareData {

    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)
            {
                condition.await();//this.wait(); //A C
            }
            //2 干活
            ++number;
            System.out.println(Thread.currentThread().getName()+"	"+number);
            //3 通知
            condition.signalAll();//this.notifyAll();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }

    public void decrement()throws Exception
    {
        lock.lock();
        try
        {
            //1 判断
            while(number == 0)
            {
                condition.await();//this.wait(); //A C
            }
            //2 干活
            --number;
            System.out.println(Thread.currentThread().getName()+"	"+number);
            //3 通知
            condition.signalAll();//this.notifyAll();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }


   /* public synchronized void increment()throws Exception
    {
        //1 判断
        while(number != 0)
        {
            this.wait(); //A C
        }
        //2 干活
        ++number;
        System.out.println(Thread.currentThread().getName()+"	"+number);
        //3 通知
        this.notifyAll();

    }

    public synchronized void decrement()throws Exception
    {
        //1 判断
        while(number == 0)
        {
            this.wait();
        }
        //2 干活
        --number;
        System.out.println(Thread.currentThread().getName()+"	"+number);
        //3 通知
        this.notifyAll();
    }*/
}

public class ProdConsumerDemo {

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

        new Thread(() -> {
            for (int i = 1; i <=10; i++)
            {
                try {
                    sd.increment();
                    Thread.sleep(200);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        },"A").start();

        new Thread(() -> {
            for (int i = 1; i <=10; i++)
            {
                try {
                    sd.decrement();
                    Thread.sleep(300);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        },"B").start();
        new Thread(() -> {
            for (int i = 1; i <=10; i++)
            {
                try {
                    sd.increment();
                    Thread.sleep(400);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        },"C").start();

        new Thread(() -> {
            for (int i = 1; i <=10; i++)
            {
                try {
                    sd.decrement();
                    Thread.sleep(500);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        },"D").start();

    }
}