多线程27 -- ReentrantLock

1.

/**
 * lock.getHoldCount()方法：只能在当前调用线程内部使用，不能再其他线程中使用
 * 那么我可以在m1方法里去调用m2方法，同时m1方法和m2方法都持有lock锁定即可 测试结果holdCount数递增
 *
 */
public class TestHoldCount {

    //重入锁
    private ReentrantLock lock = new ReentrantLock();
    
    public void m1(){
        try {
            lock.lock();
            System.out.println("进入m1方法，holdCount数为：" + lock.getHoldCount());
            
            //调用m2方法
            m2();
            
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
    
    public void m2(){
        try {
            lock.lock();
            System.out.println("进入m2方法，holdCount数为：" + lock.getHoldCount());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
    
    
    public static void main(String[] args) {
        TestHoldCount thc = new TestHoldCount();
        thc.m1();
        /*
        进入m1方法，holdCount数为：1
        进入m2方法，holdCount数为：2 */
    }
}

 2.

public class UseReentrantLock {
    
    private Lock lock = new ReentrantLock();
    
    public void method1(){
        try {
            lock.lock();
            System.out.println("当前线程:" + Thread.currentThread().getName() + "进入method1..");
            Thread.sleep(1000);
            System.out.println("当前线程:" + Thread.currentThread().getName() + "退出method1..");
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            
            lock.unlock();
        }
    }
    
    public void method2(){
        try {
            lock.lock();
            System.out.println("当前线程:" + Thread.currentThread().getName() + "进入method2..");
            Thread.sleep(2000);
            System.out.println("当前线程:" + Thread.currentThread().getName() + "退出method2..");
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            
            lock.unlock();
        }
    }
    
    public static void main(String[] args) {

        final UseReentrantLock ur = new UseReentrantLock();
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                ur.method1(); //同一把锁 ur
                ur.method2(); //同一把锁 ur
            }
        }, "t1");

        t1.start();
        try {
            Thread.sleep(10);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        //System.out.println(ur.lock.getQueueLength());
    }
    /*
    当前线程:t1进入method1..
    当前线程:t1退出method1..
    当前线程:t1进入method2..
    当前线程:t1退出method2.. */
    
}