并发编程之 ReentrantReadWriteLock

ReentrantReadWriteLock 基本用法

package com.mengweijin.learning.basic.lock;

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

/**
 * 读写锁
 *
 * @author mengweijin
 */
public class ReentrantReadWriteLockTest {
    static ReentrantReadWriteLock rrwl = new ReentrantReadWriteLock();
    static ReentrantReadWriteLock.ReadLock r = rrwl.readLock();
    static ReentrantReadWriteLock.WriteLock w = rrwl.writeLock();

    public static void main(String[] args) {
//        readWriteLock();
//        doubleWriteLock();
        doubleReadLock();
    }

    /**
     * 读写互斥
     * 先打印完 t1，再打印 t2
     */
    public static void readWriteLock() {
        new Thread(new Printer(r), "t1-read").start();
        new Thread(new Printer(w), "t2-read").start();
    }


    /**
     * 写写互斥
     * 先打印完 t1，再打印 t2
     */
    public static void doubleWriteLock() {
        new Thread(new Printer(w), "t1-read").start();
        new Thread(new Printer(w), "t2-read").start();
    }

    /**
     * 读读并发
     * t1，t2 并发执行，交替打印，谁拿到 CPU 执行权，谁就打印。
     */
    public static void doubleReadLock() {
        new Thread(new Printer(r), "t1-read").start();
        new Thread(new Printer(r), "t2-read").start();
    }

    static class Printer implements Runnable {
        private Lock lock;

        public Printer(Lock lock) {
            this.lock = lock;
        }

        @Override
        public void run() {
            lock.lock();
            try {
                for (int i = 0; i < 5; i++) {
                    print(i);
                }
            } finally {
                lock.unlock();
            }
        }

        private void print(int i) {
            try {
                System.out.println(Thread.currentThread().getName() + "：" + i);
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}