多线程: 锁的妙用之消费者,生产者的运用

有这样一个需求,每当一个生产机器生产出一个面包的时候,要等消费者消费完了再继续生产.

 

package com.ancely.fyw;

public class FoodDemo {

    private String mFoodName;//物品名
    private int mFoodId;//物品ID
    private boolean isProducted;

    public synchronized void putFood(String foodName) {
        if (!isProducted) {
            //开始生产
            mFoodId += 1;
            System.out.println(Thread.currentThread().getName() + " 生产者: 生产了: " + mFoodId);


            //已经生产完了
            isProducted = true;
            
            notifyAll();//唤醒被等待的 如果不用synchronized修饰就会报 Exception in thread "Thread-1" java.lang.IllegalMonitorStateException


            try {
//wait这个方法需要获取锁,如果不加synchronized修饰就拿不到锁就会抛异常,notify也是一样.
                wait();//它需要获取锁,然后再把这把锁给释放掉,当前线程进入等待状态,这个时候CPU就会去执行其它线程.
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public synchronized void outFood() {

        if (isProducted) {
            //可以开始消费了
            System.out.println(Thread.currentThread().getName() + " >>>>>>>>>>>>>消费者: 消费了: " + mFoodId);
            isProducted = false;

            //消费完成
            notifyAll();

            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static class ProductThread extends Thread {
        private FoodDemo mFoodDemo;

        public ProductThread(FoodDemo foodDemo) {
            mFoodDemo = foodDemo;
        }

        @Override
        public void run() {
            super.run();
            for (int i = 0; i < 20; i++) {
                mFoodDemo.putFood("面包 ");
            }
        }
    }

    public static class ConsumeThread extends Thread {
        private FoodDemo mFoodDemo;

        public ConsumeThread(FoodDemo foodDemo) {
            mFoodDemo = foodDemo;
        }

        @Override
        public void run() {
            super.run();
            for (int i = 0; i < 20; i++) {
                mFoodDemo.outFood();
            }
        }
    }

    public static void main(String[] args) {

        FoodDemo foodDemo = new FoodDemo();
        new ProductThread(foodDemo).start();
        new ConsumeThread(foodDemo).start();
    }
}

打印结果如下

Thread-0 生产者: 生产了: 1
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 1
Thread-0 生产者: 生产了: 2
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 2
Thread-0 生产者: 生产了: 3
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 3
Thread-0 生产者: 生产了: 4
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 4
Thread-0 生产者: 生产了: 5
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 5
Thread-0 生产者: 生产了: 6
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 6
Thread-0 生产者: 生产了: 7
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 7
Thread-0 生产者: 生产了: 8
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 8
Thread-0 生产者: 生产了: 9
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 9
Thread-0 生产者: 生产了: 10
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 10
Thread-0 生产者: 生产了: 11
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 11
Thread-0 生产者: 生产了: 12
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 12
Thread-0 生产者: 生产了: 13
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 13
Thread-0 生产者: 生产了: 14
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 14
Thread-0 生产者: 生产了: 15
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 15
Thread-0 生产者: 生产了: 16
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 16
Thread-0 生产者: 生产了: 17
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 17
Thread-0 生产者: 生产了: 18
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 18
Thread-0 生产者: 生产了: 19
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 19
Thread-0 生产者: 生产了: 20
Thread-1 >>>>>>>>>>>>>消费者: 消费了: 20