学会显示地使用Lock

最新推荐文章于 2025-07-19 10:09:33 发布

原创最新推荐文章于 2025-07-19 10:09:33 发布 · 120 阅读

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本文探讨了并发环境下整数生成类的实现，通过使用Lock对象和synchronized关键字来确保线程安全。实例展示了如何在多线程环境中正确生成互斥的偶数，并在生成过程中检查是否达到终止条件。

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Lock对象在使用的时候必须被显示地创建、锁定和释放。它和synchronized关键字的作用类似，举一个例子如下：

======================整数生成类
public abstract class IntGenerator {

private volatile boolean canceled=false;

public abstract int next();

public void cancel()
{ this.canceled=false;
}

public boolean isCanceled()
{
return this.canceled;
}

}

===========================实现类
public class MutexEvenGenerator extends IntGenerator{
private int currentEvenValue=0;
private java.util.concurrent.locks.Lock lock=new ReentrantLock();

@Override
public int next() {
// TODO Auto-generated method stub
try {
lock.lock();
++currentEvenValue;
Thread.yield();
++currentEvenValue;
return currentEvenValue;
}finally{

lock.unlock();
}
}

public static void main(String[] args){

EvenChecker.test(new MutexEvenGenerator(),10);
}
}

================================
public class EvenChecker implements Runnable{
private IntGenerator generator;
private final int id;

public EvenChecker(IntGenerator generator,int id) {
// TODO Auto-generated constructor stub
this.generator=generator;
this.id=id;
}

@Override
public void run() {
// TODO Auto-generated method stub
while(!generator.isCanceled())
{
int val=generator.next();
if(val%2!=0)
{
System.out.println(val+ " is not even!");
generator.cancel();
}
else
{
//System.out.println(val+" is even!");
}
}

}

public static void test(IntGenerator gp,int count)
{

System.out.println("Press Ctrl+C to Exit");
ExecutorService exec=Executors.newCachedThreadPool();
for(int i=0;i<count;i++)
exec.execute(new EvenChecker(gp,i));
}

public static void test(IntGenerator gp)
{
test(gp,10);
}

}