关于JAVA锁的问题，请问这段代码哪有问题，如何实现这个需求？

[kamikameha]

想锁住一个处理过程，但是这个处理过程分两步，而且两步分别在两个不同的线程中执行。
整个处理过程只能被一个用户所独占，如果出现抢占，后来者需要等待。大致写了个原型代码，可发现不起作用，请教一下代码里有什么问题，该如何完成这个工作？多谢

package main;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

public class LockTest {
public static ReentrantLock locker = new ReentrantLock();
public static Condition cond = null;
public static boolean WINNER = true;

public class PhaseTow extends Thread {
public void run() {
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
}

cond.signal();
locker.unlock();
SingleTest.WINNER = false;
}
}

public class PhaseOne extends Thread {
public void run() {
if (!SingleTest.WINNER) {
try {
cond.await();
} catch (Exception exp) {
}
}

SingleTest.WINNER = true;
cond = locker.newCondition();
locker.lock();

try {
Thread.sleep(3000);
} catch (InterruptedException e) {
}

PhaseTow tow = new PhaseTow();
tow.start();
}
}

public static void main(String[] args) {
LockTest obj = new LockTest();

for (int i = 0; i < 10; i++) {
PhaseOne element = obj.new PhaseOne();
element.start();

try {
Thread.sleep(100);
} catch (InterruptedException e) {
}
}
}
}