B9 Concurrent 重入锁（ReentrantLock）

import java.util.concurrent.locks.ReentrantLock;

public class Main {

	public static void main(String[] args) {
		Command c = new Command();
		int nThreads = 5;
		for(int i = 0; i < nThreads; i++){
			new Thread(c).start();
		}
	}

}

class Command implements Runnable {
	
	ReentrantLock lock = new ReentrantLock();
	
	@Override
	public void run() {
		try{
			lock.lock();
			System.out.println(Thread.currentThread().getName() + ": 获得锁！");
		}catch(Exception e){
			//处理异常
		}finally{
			System.out.println(Thread.currentThread().getName() + ": 释放锁！");
			lock.unlock();
		}
	}
}