将一个线程置于休眠状态，直到在另一个线程中解决某个条件

这里有两个代码块，它们完成了（我认为是）同样的事情。

我基本上正在尝试学习如何使用Java 1.5的并发性来摆脱Thread.sleep（long）。第一个示例使用 ReentrantLock，第二个示例使用 CountDownLatch。我试图做的是将一个线程置于休眠状态，直到在另一个线程中解决条件。

ReentrantLock 在我用来决定是否唤醒另一个线程的布尔值上提供了一个锁，然后我使用 Condition with await/signal 来休眠另一个线程。据我所知，我需要使用锁的唯一原因是如果多个线程需要对布尔值的写入访问权限。

CountDownLatch似乎提供了与ReentrantLock相同的功能，但没有（不必要的？）锁。但是，感觉我通过仅用一个必要的倒计时来初始化它来劫持它的预期用途。我认为它应该在多个线程将处理同一任务时使用，而不是当多个线程等待一个任务时。

所以，问题：

1. 我是否在 ReentrantLock 代码中将锁用于“正确的事情”？如果我只在一个线程中写入布尔值，那么锁是必需的吗？只要我在唤醒任何其他线程之前重置布尔值，我就不会造成问题，不是吗？

2. 有没有一个类似于CountDownLatch的类可以用来避免锁（假设我应该在这种情况下避免它们）更适合这个任务？

3. 有没有其他方法可以改进我应该注意的代码？

示例一：

import java.util.concurrent.locks.*;

public class ReentrantLockExample extends Thread {

//boolean - Is the service down?
boolean serviceDown;

// I am using this lock to synchronize access to sDown
Lock serviceLock; 
// and this condition to sleep any threads waiting on the service.
Condition serviceCondition;

public static void main(String[] args) {
    Lock l = new ReentrantLock();
    Condition c = l.newCondition(); 
    ReentrantLockExample rle = new ReentrantLockExample(l, c);

    //Imagine this thread figures out the service is down
    l.lock();
    try {
        rle.serviceDown = true;
    } finally {
        l.unlock();
    }

    int waitTime = (int) (Math.random() * 5000);
    System.out.println("From main: wait time is " + waitTime);
    rle.start();
    try {
        //Symbolizes some random time that the service takes to come back up.
        Thread.sleep(waitTime);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }

    //Imagine this thread figures out that the service is back up.
    l.lock();
    try {
        rle.serviceDown = false;
        c.signal();
    } finally {
        l.unlock();
    }

}

//Constructor
public ReentrantLockExample(Lock l, Condition c) {  
    this.serviceLock = l;
    this.serviceCondition = c; 
}

/*
 * Should wait for this imaginary service to come back online.
 */
public void run() {
    System.out.println("Thread: start awaiting");
    serviceLock.lock();
    try {
        while (isServiceDown())
        {           
            serviceCondition.await();
        }
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } finally {
        serviceLock.unlock();
    }
    System.out.println("Thread: done awaiting");
}


private boolean isServiceDown() {       
    return serviceDown;
}
}

示例二：

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.*;

public class CountDownLatchExample extends Thread {

    //boolean - Is the service down?
    boolean serviceDown;

    // I am using this latch to wait on the service.
    CountDownLatch serviceLatch; 


    public static void main(String[] args) {
        CountDownLatch cdl = new CountDownLatch(1);     
        CountDownLatchExample cdle = new CountDownLatchExample(cdl);

        //Service goes down.
        cdle.serviceDown = true;        

        int waitTime = (int) (Math.random() * 5000);
        System.out.println("From main: wait time is " + waitTime);
        cdle.start();
        try {
            //Symbolizes some random time that the service takes to come back up.
            Thread.sleep(waitTime);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        //Service comes back up.
        cdle.serviceDown = false;
        cdl.countDown();    
    }

    //Constructor 
    public CountDownLatchExample(CountDownLatch cdl) {  
        this.serviceLatch = cdl;         
    }

    /*
     * Should wait for this imaginary service to come back online.
     */
    public void run() {
        System.out.println("Thread: start awaiting");
        try {
            while (isServiceDown()) {           
                serviceLatch.await();
            }
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("Thread: done awaiting");
    }

    private boolean isServiceDown() {       
        return serviceDown;
    }
}