Java多线程 之 lock与condition的使用（十四）

在博文 Java多线程 之 wait、notifyAll（十二） 中使用wait、notify使“打蜡”和“抛光”两个任务能够协同工作，本文阐述使用lock、condition来实现。而且使用signalAll要比使用notifyAll更安全。

1.使用抛出异常

package org.fan.learn.thread.testCondition;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.AbstractQueuedSynchronizer;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;/** * Created by fan on 2016/7/4. */class Car {    private ReentrantLock reentrantLock = new ReentrantLock();    private Condition condition = reentrantLock.newCondition();    private boolean waxOn = false;    //同步方法    //打蜡    void waxing() {        reentrantLock.lock();        try {            waxOn = true;            condition.signalAll();        } finally {            reentrantLock.unlock();        }    }    //同步方法    //抛光    void buffing() {        reentrantLock.lock();        try {            waxOn = false;            condition.signalAll();        } finally {            reentrantLock.unlock();        }    }    //同步方法    //等待打蜡完成    void waitForWaxing() throws InterruptedException {        reentrantLock.lock();        try {            while (!waxOn) {                condition.await();            }        } finally {            reentrantLock.unlock();        }    }    //同步方法    //等待抛光完成    void waitForBuffing() throws InterruptedException {        reentrantLock.lock();        try {            while (waxOn) {                condition.await();            }        }  finally {            reentrantLock.unlock();        }    }}//打蜡任务//一次打蜡完成，需要等待抛光完成之后才能继续打蜡class WaxingTask implements Runnable {    private Car car;    public WaxingTask(Car car) {        this.car = car;    }    public void run() {        try {            while (!Thread.interrupted()) {                System.out.println("waxing");                TimeUnit.MILLISECONDS.sleep(200);                car.waxing();                car.waitForBuffing();            }        } catch (InterruptedException e) {            //打印异常堆栈            e.printStackTrace();        }        System.out.println("Ending Waxing Task");    }}//抛光任务//在抛光之前必须要先打蜡，需要等待打蜡完成才能抛光class BuffingTask implements Runnable {    private Car car;    public BuffingTask(Car car) {        this.car = car;    }    public void run() {        try {            while (!Thread.interrupted()) {                car.waitForWaxing();                System.out.println("Buffing");                TimeUnit.MILLISECONDS.sleep(200);                car.buffing();            }        } catch (InterruptedException e) {            //打印异常堆栈            e.printStackTrace();        }        System.out.println("Ending Buffering Task");    }}public class WaxingBuffing {    public static void main(String[] args) throws InterruptedException {        Car car = new Car();        ExecutorService exe = Executors.newCachedThreadPool();        exe.execute(new WaxingTask(car));        exe.execute(new BuffingTask(car));        TimeUnit.SECONDS.sleep(5);        //向所有任务发送interrupt()信号        exe.shutdownNow();        System.out.println("main exit");    }}

使用抛出异常的输出：

waxingBuffingwaxingBuffingwaxingBuffingwaxingBuffingwaxingmain exitEnding Waxing Taskjava.lang.InterruptedException: sleep interruptedEnding Buffering Task    at java.lang.Thread.sleep(Native Method)    at java.lang.Thread.sleep(Thread.java:340)    at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)    at org.fan.learn.thread.testCondition.WaxingTask.run(WaxingBuffing.java:110)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)    at java.lang.Thread.run(Thread.java:745)java.lang.InterruptedException    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.reportInterruptAfterWait(AbstractQueuedSynchronizer.java:2014)    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2048)    at org.fan.learn.thread.testCondition.Car.waitForWaxing(WaxingBuffing.java:49)    at org.fan.learn.thread.testCondition.BuffingTask.run(WaxingBuffing.java:134)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)    at java.lang.Thread.run(Thread.java:745)Process finished with exit code 0

2.使用catch异常：

package org.fan.learn.thread.testCondition;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.AbstractQueuedSynchronizer;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;/** * Created by fan on 2016/7/4. */class Car {    private ReentrantLock reentrantLock = new ReentrantLock();    private Condition condition = reentrantLock.newCondition();    private boolean waxOn = false;    //同步方法    //打蜡    void waxing() {        reentrantLock.lock();        try {            waxOn = true;            condition.signalAll();        } finally {            reentrantLock.unlock();        }    }    //同步方法    //抛光    void buffing() {        reentrantLock.lock();        try {            waxOn = false;            condition.signalAll();        } finally {            reentrantLock.unlock();        }    }    //同步方法    //等待打蜡完成    void waitForWaxing() {        reentrantLock.lock();        try {            while (!waxOn) {                condition.await();            }        } catch (InterruptedException e) {            e.printStackTrace();        } finally {            reentrantLock.unlock();        }    }    //同步方法    //等待抛光完成    void waitForBuffing()  {        reentrantLock.lock();        try {            while (waxOn) {                condition.await();            }        } catch (InterruptedException e) {            e.printStackTrace();        } finally {            reentrantLock.unlock();        }    }}//打蜡任务//一次打蜡完成，需要等待抛光完成之后才能继续打蜡class WaxingTask implements Runnable {    private Car car;    public WaxingTask(Car car) {        this.car = car;    }    public void run() {        try {            while (!Thread.interrupted()) {                System.out.println("waxing");                TimeUnit.MILLISECONDS.sleep(200);                car.waxing();                car.waitForBuffing();            }        } catch (InterruptedException e) {            //打印异常堆栈            e.printStackTrace();        }        System.out.println("Ending Waxing Task");    }}//抛光任务//在抛光之前必须要先打蜡，需要等待打蜡完成才能抛光class BuffingTask implements Runnable {    private Car car;    public BuffingTask(Car car) {        this.car = car;    }    public void run() {        try {            while (!Thread.interrupted()) {                car.waitForWaxing();                System.out.println("Buffing");                TimeUnit.MILLISECONDS.sleep(200);                car.buffing();            }        } catch (InterruptedException e) {            //打印异常堆栈            e.printStackTrace();        }        System.out.println("Ending Buffering Task");    }}public class WaxingBuffing {    public static void main(String[] args) throws InterruptedException {        Car car = new Car();        ExecutorService exe = Executors.newCachedThreadPool();        exe.execute(new WaxingTask(car));        exe.execute(new BuffingTask(car));        TimeUnit.SECONDS.sleep(5);        //向所有任务发送interrupt()信号        exe.shutdownNow();        System.out.println("main exit");    }}

这个无法正常结束。。
在waitForWaxing中catch异常之后，无法继续执行了。因此需要往外抛。
对于异常：如果一个方法A中捕获异常，调用该方法Ａ的方法Ｂ则无法正常退出，需要Ａ方法抛出异常，由方法Ｂ捕获，这时执行完catch之后可以继续执行方法Ｂ中的语句。
使用catch异常的输出：

waxingBuffingwaxingBuffingwaxingmain exitjava.lang.InterruptedException: sleep interrupted    at java.lang.Thread.sleep(Native Method)    at java.lang.Thread.sleep(Thread.java:340)    at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)    at org.fan.learn.thread.testCondition.WaxingTask.run(WaxingBuffing.java:110)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)    at java.lang.Thread.run(Thread.java:745)java.lang.InterruptedException    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.reportInterruptAfterWait(AbstractQueuedSynchronizer.java:2014)    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2048)    at org.fan.learn.thread.testCondition.Car.waitForWaxing(WaxingBuffing.java:61)    at org.fan.learn.thread.testCondition.BuffingTask.run(WaxingBuffing.java:134)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)    at java.lang.Thread.run(Thread.java:745)Ending Waxing TaskBuffing