Lock的使用

使用RentrantLock类

在Java多线程中，可以使用synchronized关键字来实现线程之间同步互斥，但在JDK1.5之后加入了RentrantLock类也能达到同样的效果，并且在扩展功能上的也更强大。比如具有嗅探锁定、多路分支通知等功能，在使用上比synchronized更加灵活。

实现同步1

调用lock加锁，unlock解锁

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

public class RentrantLockTest {

    private Lock lock = new ReentrantLock();

    private int count = 0;

    public void test() {
        lock.lock();
        for (int i = 0; i < 5; i++) {
             System.out.println("ThreadName" + Thread.currentThread().getName() + " i = " + i);
        }
        lock.unlock();
    }

    public static void main(String[] args) {
        RentrantLockTest test = new RentrantLockTest();
        ThreadA t1 = new ThreadA(test);
        t1.start();
        ThreadA t2 = new ThreadA(test);
        t2.start();
        ThreadA t3 = new ThreadA(test);
        t3.start();
    }
}

class ThreadA extends Thread {
    private RentrantLockTest test;
    public ThreadA(RentrantLockTest test) {
        this.test = test;
    }
    @Override
    public void run() {
        super.run();
        test.test();
    }
}

运行结果：

ThreadNameThread-0 i = 0
ThreadNameThread-0 i = 1
ThreadNameThread-0 i = 2
ThreadNameThread-0 i = 3
ThreadNameThread-0 i = 4
ThreadNameThread-1 i = 0
ThreadNameThread-1 i = 1
ThreadNameThread-1 i = 2
ThreadNameThread-1 i = 3
ThreadNameThread-1 i = 4
ThreadNameThread-2 i = 0
ThreadNameThread-2 i = 1
ThreadNameThread-2 i = 2
ThreadNameThread-2 i = 3
ThreadNameThread-2 i = 4

当前线程释放锁后其他线程才能获取锁。