java编程思想笔记-并发之线程协作(三)

Condition类简介

使用互斥并允许任务挂起的基本类是Condition，可以使用Condition上的await()来挂起一个任务，可以使用signal()通知一个任务，signalAll()唤醒所有在这个Condition上挂起的任务，与notifyAll()相比，signalAll()是更安全的方式，同时任务在调用await(),signal()或者signalAll()必须拥有这个锁

使用concurrent类库的Condition重写汽车打蜡抛光的例子

package com.tij.thread.cooperate;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

class Car2 {
private Lock lock = new ReentrantLock();
//使用lock创建一个condition对象，管理任务通信
private Condition condition = lock.newCondition();
private boolean waxOn = false;

public void waxed() {
lock.lock();
//使用try-finally保证在所有情况下释放锁
try {
waxOn = true;
condition.signalAll();
} finally {
lock.unlock();
}
}

public void buffed() {
lock.lock();
try {
waxOn = false;
condition.signalAll();
} finally {
lock.unlock();
}
}

// 必须让线程获取锁线程才能wait
public void waitForWaxing() throws InterruptedException {
lock.lock();
try {
while (!waxOn) {
condition.await();
}
} finally {
lock.unlock();
}
}

// 必须让线程获取锁线程才能wait
public void waitForBuffing() throws InterruptedException {
lock.lock();
try {
while (waxOn) {
condition.await();
}
} finally {
lock.unlock();
}
}
}

class WaxOn2 implements Runnable {
private Car car;

public WaxOn2(Car car) {
this.car = car;
}

@Override
public void run() {
try {
while (!Thread.interrupted()) {
System.out.println(" Wax On ");
TimeUnit.MILLISECONDS.sleep(200);
car.waxed();
car.waitForBuffing();
}
} catch (InterruptedException e) {
System.out.println("WaxOn Exiting via interrupt ");
}
System.out.println(" Ending Wax On task ");
}
}

class WaxOff2 implements Runnable {
private Car car;

public WaxOff2(Car car) {
this.car = car;
}

@Override
public void run() {
try {
while (!Thread.interrupted()) {
car.waitForWaxing();
System.out.println(" Wax Off ! ");
TimeUnit.MILLISECONDS.sleep(200);
car.buffed();
}
} catch (Exception e) {
System.out.println("WaxOff Exiting via interrupt ");
}
System.out.println(" Ending Wax Off task ");
}
}

public class WaxOMatic2 {
public static void main(String[] args) throws InterruptedException {
Car car = new Car();
ExecutorService exec = Executors.newCachedThreadPool();
exec.execute(new WaxOff(car));
exec.execute(new WaxOn(car));
TimeUnit.SECONDS.sleep(5);
exec.shutdownNow();
}
}