Lock自定义锁重入

 编写一个类，实现Lock接口，重写lock（）和unlock（）方法。

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

public class MyLock implements Lock {
	private boolean isLocked = false;   //是否等待
	private Thread lockBy = null;    //记录当前线程
	private int lockCount = 0;     //重入次数

	@Override
	public synchronized void lock() {
		
		Thread currentThread = Thread.currentThread();
		
		while (isLocked && currentThread != lockBy)
			try {
				wait();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		isLocked = true;
		lockBy = currentThread;
		lockCount ++; 
	}
	
	@Override
	public synchronized void unlock() {
		if(lockBy == Thread.currentThread()) {
			lockCount --;  // 1  0
			
			if(lockCount == 0) {
				notify();
				isLocked = false;
			}
		}
	}
}

测试可重入：

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

public class Demo {
	
	Lock lock = new MyLock();
	
	public void a() {
		lock.lock();
		System.out.println("a");
		b();
		lock.unlock();
	}
	
	public void b() {
		lock.lock();
		System.out.println("b");
		c();
		lock.unlock();
	}
	
	public void c() {
		lock.lock();
		System.out.println("c");
		lock.unlock();
	}
	
	public static void main(String[] args) {
		Demo d = new Demo();
		
		new Thread(new Runnable() {
			
			@Override
			public void run() {
				d.a();
			}
		}).start();
		
//		new Thread(new Runnable() {
//			
//			@Override
//			public void run() {
//				d.b();
//			}
//		}).start();
	}
}