JAVA and C++版信号量（PV操作）

import java.util.concurrent.Semaphore;
/**
* 抽象任务，具体的执行任务，归实现类负责
*
* @author Administrator
*
*/
public abstract class Task {
public abstract void run();
private Semaphore s;
private boolean hasExisted = false;
public void P(final Semaphore s) throws InterruptedException {
if (s == null) { // 申请空的信号量
throw new InterruptedException("不能为空");
}
if (hasExisted) {// 已经申请了一个资源，还没有释放
throw new InterruptedException("已经占用一个资源");
}
s.acquire();// 阻塞
this.s = s;
hasExisted = true;
}
public boolean V() {
if (!hasExisted) {
return false;// 没沾有资源就不能说释放了
}
s.release();//释放资源
hasExisted = false;
s = null;
return true;
}
}
import java.util.concurrent.Semaphore;
/**
* 用信号量实现互斥
*
* @author Administrator
*
*/
public class Mutex extends Semaphore {
private static final long serialVersionUID = 1L;
public Mutex() {
super(1);//互斥是1
}
} import java.util.concurrent.Semaphore;
public class Test {
public static void main(String[] args) {
// final Semaphore s = new Semaphore(2);//信号量，执行结果run the task1 run the
// task2 run the task3
final Semaphore s = new Mutex();// 互斥 run the task1 run the task2 run
// the task3
new Thread() {
public void run() {
Task1 task2 = new Task1();
try {
task2.P(s);// 申请资源
task2.run();// 执行任务
task2.V();// 释放资源
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}.start();
new Thread() {
public void run() {
Task2 task2 = new Task2();
try {
task2.P(s);
task2.run();
task2.V();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}.start();
new Thread() {
public void run() {
Task3 task2 = new Task3();
try {
task2.P(s);
task2.run();
task2.V();
} catch (InterruptedException e)