线程 lock 问题 请教高手

[wb821147966]

请高手帮忙为这个程序写一下注释 让菜鸟我更容易理解
//: concurrency/AttemptLocking.java
// Locks in the concurrent library allow you
// to give up on trying to acquire a lock.
import java.util.concurrent.*;
import java.util.concurrent.locks.*;

public class AttemptLocking {
private ReentrantLock lock = new ReentrantLock();
public void untimed() {
boolean captured = lock.tryLock();
try {
System.out.println("tryLock(): " + captured);
} finally {
if(captured)
lock.unlock();
}
}
public void timed() {
boolean captured = false;
try {
captured = lock.tryLock(2, TimeUnit.SECONDS);
} catch(InterruptedException e) {
throw new RuntimeException(e);
}
try {
System.out.println("tryLock(2, TimeUnit.SECONDS): " +
captured);
} finally {
if(captured)
lock.unlock();
}
}
public static void main(String[] args) {
final AttemptLocking al = new AttemptLocking();
al.untimed(); // True -- lock is available
al.timed(); // True -- lock is available
// Now create a separate task to grab the lock:
new Thread() {
{ setDaemon(true); }
public void run() {
al.lock.lock();
System.out.println("acquired");
}
}.start();
Thread.yield(); // Give the 2nd task a chance
al.untimed(); // False -- lock grabbed by task
al.timed(); // False -- lock grabbed by task
}
} /* Output:
tryLock(): true
tryLock(2, TimeUnit.SECONDS): true
acquired
tryLock(): false
tryLock(2, TimeUnit.SECONDS): false
*///:~



请高手帮忙为这个程序写一下注释 让菜鸟我更容易理解 特别是这一句： al.lock.lock();
万分感谢

[老紫竹]

1 单独获得锁都没有问题
2 如果有另一个线程在争夺锁时就得看谁先拿到了
3 al.lock.lock(); 这个是简单的使用啊，是 al对象的 lock 属性，调用了它的lock()方法，拿到了锁

4 此程序根据线程启动的速度和系统调度不同，每次运行结果很可能不同。 那个tryLock():由于先调用，且为立即拿到锁，成功的几率稍大一些

[wb821147966]

是不是 timed untimed 和 Thread
同时去抢“lock”对象这把锁

[老紫竹]

http://www.java2000.net/viewthread.jsp?tid=3756

[hmsuccess]

[Quote=引用 3 楼 java2000_net 的回复:]
http://www.java2000.net/viewthread.jsp?tid=3756
[/Quote]
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