模拟jdk1.5中reentrantlock

选自：java线程2e。
类似于jdk1.5中的reentrantlock实现。

package com.cxz.tools;

public class BusyFlag {
	protected Thread busyFlag = null;

	protected int busyCount = 0;

	public synchronized void getBusyFlag() throws InterruptedException {
		while (tryGetBusyFlag() == false) {
			wait();
		}
	}

	public synchronized void freeBusyFlag() {
		if (busyFlag == Thread.currentThread()) {
			busyCount--;
			if (busyCount == 0) {
				busyFlag = null;
				notify();
			}
		}
	}

	private boolean tryGetBusyFlag() {
		if (busyFlag == null) {
			busyFlag = Thread.currentThread();
			busyCount = 1;
			return true;
		}
		if (busyFlag == Thread.currentThread()) {
			busyCount++;
			return true;
		}
		return false;
	}
}