多線程: 鎖的妙用之消費者,生產者的運用

有這樣一個需求,每當一個生產機器生產出一個麪包的時候,要等消費者消費完了再繼續生產.

 

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) {
            //開始生產
            mFoodId += 1;
            System.out.println(Thread.currentThread().getName() + " 生產者: 生產了: " + mFoodId);


            //已經生產完了
            isProducted = true;
            
            notifyAll();//喚醒被等待的 如果不用synchronized修飾就會報 Exception in thread "Thread-1" java.lang.IllegalMonitorStateException


            try {
//wait這個方法需要獲取鎖,如果不加synchronized修飾就拿不到鎖就會拋異常,notify也是一樣.
                wait();//它需要獲取鎖,然後再把這把鎖給釋放掉,當前線程進入等待狀態,這個時候CPU就會去執行其它線程.
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public synchronized void outFood() {

        if (isProducted) {
            //可以開始消費了
            System.out.println(Thread.currentThread().getName() + " >>>>>>>>>>>>>消費者: 消費了: " + mFoodId);
            isProducted = false;

            //消費完成
            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("麪包 ");
            }
        }
    }

    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();
    }
}

打印結果如下

Thread-0 生產者: 生產了: 1
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 1
Thread-0 生產者: 生產了: 2
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 2
Thread-0 生產者: 生產了: 3
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 3
Thread-0 生產者: 生產了: 4
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 4
Thread-0 生產者: 生產了: 5
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 5
Thread-0 生產者: 生產了: 6
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 6
Thread-0 生產者: 生產了: 7
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 7
Thread-0 生產者: 生產了: 8
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 8
Thread-0 生產者: 生產了: 9
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 9
Thread-0 生產者: 生產了: 10
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 10
Thread-0 生產者: 生產了: 11
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 11
Thread-0 生產者: 生產了: 12
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 12
Thread-0 生產者: 生產了: 13
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 13
Thread-0 生產者: 生產了: 14
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 14
Thread-0 生產者: 生產了: 15
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 15
Thread-0 生產者: 生產了: 16
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 16
Thread-0 生產者: 生產了: 17
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 17
Thread-0 生產者: 生產了: 18
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 18
Thread-0 生產者: 生產了: 19
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 19
Thread-0 生產者: 生產了: 20
Thread-1 >>>>>>>>>>>>>消費者: 消費了: 20