JAVA多线程学习------ReentrantLock学习

1.ReentrantLock与synchronized对比

相对于 synchronized 它具备如下特点 可中断 可以设置超时时间 可以设置为公平锁 支持多个条件变量 与 synchronized 一样，都支持可重入 基本语法：

lock.lock();
        try {
            
        }finally {
            lock.unlock();
        }
           

2.可重入

package com.xjq.ThreadDemo;


import sun.plugin.ClassLoaderInfo;

import java.util.concurrent.locks.ReentrantLock;

public class ReentrantLockDemo {
    private static  ReentrantLock lock = new ReentrantLock();
    public static void main(String[] args) {
        lock.lock();
        try {
            System.out.println("mian 方法 lock");
            m1();
        }finally {
            lock.unlock();
        }
    }
    public static  void m1(){
        lock.lock();
        try {
            System.out.println("m1  方法locK");
            m2();
        }finally {
            lock.unlock();
        }
    }
    public  static  void m2(){
        lock.lock();
        try{
            System.out.println("m2   方法lock");
        }finally {
            lock.unlock();
        }

    }
}
           

3.可中断

package com.xjq.ThreadDemo;

import java.util.concurrent.locks.ReentrantLock;

/**
 * 可中断性
 */
public class ReentrantLockDemo01 {
    private static ReentrantLock lock = new ReentrantLock();
    public static void main(String[] args) {
        Thread t1 = new Thread(() -> {
            try {
                lock.lockInterruptibly();     //可打断lock
                System.out.println("t1  进入lock。。。。。");
                Thread.sleep(2000);         
                System.out.println("睡眠结束了。。。。");
            } catch (InterruptedException e) {
                System.out.println("t1线程被打断了");
                //e.printStackTrace();
            }finally {
                lock.unlock();   //解锁
            }
        }, "t1");
        Thread t2 = new Thread(() -> {
            lock.lock();
            try{
                System.out.println("t2  进入lock。。。。");
                t1.interrupt();      //打断t1线程
                System.out.println("打断t1 进程");

            }finally {
                lock.unlock();
            }
        }, "t2");

        t1.start();
        t2.start();
    }

}
           

执行结果：

t2  进入lock。。。。

打断t1 进程

t1线程被打断了

Exception in thread "t1" java.lang.IllegalMonitorStateException

    at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:151)

    at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1261)

    at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:457)

    at com.xjq.ThreadDemo.ReentrantLockDemo01.lambda$main$0(ReentrantLockDemo01.java:21)

    at java.lang.Thread.run(Thread.java:748)

4.可设置超时时间

package com.xjq.ThreadDemo;

import java.sql.Time;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 设置超时时间
 * t1 占用锁，t2设置超时时间
 */
public class ReentrantLockDemo02 {
    private static ReentrantLock lock = new ReentrantLock();
    public static void main(String[] args) {
        Thread t1 = new Thread(() -> {
           lock.lock();
            try {
                System.out.println("t1 获取到锁。。。。。");
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }finally {
                lock.unlock();
            }
        }, "t1");
        Thread t2 = new Thread(() -> {
            try {
                if (!lock.tryLock(2, TimeUnit.SECONDS)) {  //tryLock()和tryLock(long,单位) 获取到锁返回值为true，否则返回为false
                   System.out.println("t2没有获取到锁");
                    return;
                }
                System.out.println("t2  获取到锁。。。。");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }finally {
                lock.unlock();
            }
        }, "t2");

        t1.start();
        t2.start();
    }

}