java线程间协作——wait()、notify()、notifyAll()

古城微笑少年丶 2022-05-20 23:05 156阅读 0赞

本文主要介绍进程间的协作。

经常会有一个这样的问题，就是两个线程交替进行执行，当一个线程执行完成后，再执行另一个线程。

那么现在我尝试些一个这样的程序：

先扫地，再拖地，一直循环下去。

1、先写一个控制扫地和拖地的调度器。

package com.xueyou.demo.threadcoopreate;
    
    public class SweepAndMopDispacher {
        private boolean isSweeping = false;
    
        public synchronized void sweeped() {
            isSweeping = true;
            notifyAll();
        }
    
        public synchronized void Mopped() {
            isSweeping = false;
            notifyAll();
        }
    
        public synchronized void waitForSweeped() throws InterruptedException {
            while (isSweeping == false) {
                wait();
            }
        }
    
        public synchronized void waitForMopped() throws InterruptedException {
            while (isSweeping == true) {
                wait();
            }
        }
    }

2、然后分别写拖地和扫地的逻辑。

package com.xueyou.demo.threadcoopreate;
    
    import java.util.concurrent.TimeUnit;
    
    public class SweepRunner implements Runnable {
        private SweepAndMopDispacher dispacher;
    
        public SweepRunner(SweepAndMopDispacher dispacher) {
            this.dispacher = dispacher;
        }
    
        @Override
        public void run() {
            try {
                while (!Thread.interrupted()) {
                    System.out.println(Thread.currentThread().getName() + "扫地..");
                    TimeUnit.MILLISECONDS.sleep(800);
                    dispacher.sweeped();
                    dispacher.waitForMopped();
                }
            } catch (InterruptedException e) {
                System.out.println("exit by interrupted");
            } finally {
                System.out.println("mop exit;");
            }
        }
    }
    
    
    package com.xueyou.demo.threadcoopreate;
    
    import sun.util.locale.provider.TimeZoneNameUtility;
    
    import java.util.concurrent.TimeUnit;
    
    public class MopRunner implements Runnable {
        private SweepAndMopDispacher dispacher;
    
        public MopRunner(SweepAndMopDispacher dispacher) {
            this.dispacher = dispacher;
        }
    
        @Override
        public void run() {
            try {
                while (!Thread.interrupted()) {
                    System.out.println(Thread.currentThread().getName() + "拖地..");
                    TimeUnit.MILLISECONDS.sleep(800);
                    dispacher.Mopped();
                    dispacher.waitForSweeped();
                }
            } catch (InterruptedException e) {
                System.out.println("exit by interrupted");
            } finally {
                System.out.println("Mop runner exit;");
            }
        }
    }

3、编写一个测试程序进行测试

package com.xueyou.demo.threadcoopreate;
    
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import java.util.concurrent.TimeUnit;
    
    
    public class TestMain {
        public static void main(String[] args) {
            SweepAndMopDispacher dispacher = new SweepAndMopDispacher();
            ExecutorService executorService = Executors.newCachedThreadPool();
            executorService.submit(new SweepRunner(dispacher));
            executorService.submit(new MopRunner(dispacher));
            try {
                TimeUnit.SECONDS.sleep(4);
                executorService.shutdownNow();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
        }
    }

运行结果：

![70][]

需要注意的是这里面的结束是通过shutodownNow()实现的。

而在每个实现的Runnable的接口里面也是通过捕获interrupted状态或者异常来实现结束的。

[70]: /images/20220521/2a35bca52f484eb4a1267cf3473f268c.png