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  • ReadWriteLock 读写锁(读书笔记)

     读写分离锁可以有效的帮助减少锁的竞争,提升系统的效率,
    • 读-读不互斥 读读之间不阻塞
    • 读-写互斥 读阻塞写,写也会阻塞读
    • 写-写互斥 写写阻塞 
    在系统中,读操作次数远远大于写操作,则读写锁就可以发挥最大的功效,提升系统的性能.
    public class ReadWriteLockDemo {
        private static Lock lock = new ReentrantLock();
        private static ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();
        private static Lock readLock = readWriteLock.readLock();
        private static Lock writeLock = readWriteLock.writeLock();
        private int value;
    
        public Object handleRead(Lock lock) throws InterruptedException {
            try {
                lock.lock();
                Thread.sleep(1000);//模拟读操作
                return value;
            } finally {
                lock.unlock();
            }
        }
    
        public void handleWrite(Lock lock, int index) throws InterruptedException {
            try {
                lock.lock();
                Thread.sleep(1000);
                this.value = index;
            } finally {
                lock.unlock();
            }
        }
    
        public static void main(String[] args) {
            final ReadWriteLockDemo demo = new ReadWriteLockDemo();
            Runnable readRunnable = () -> {
                try {
                    Object o = demo.handleRead(readLock);//读写锁
                    // Object o1 = demo.handleRead(lock);//普通锁
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            };
            Runnable writeRunnable = () -> {
                try {
                    demo.handleWrite(writeLock, new Random().nextInt());//读写锁
                    //demo.handleWrite(lock, new Random().nextInt());//普通锁
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            };
    
            for (int i = 0; i < 18; i++) {
                new Thread(readRunnable).start();
            }
            for (int i = 18; i < 20; i++) {
                new Thread(writeRunnable).start();
            }
        }
    }
     
    我们分别使用重入锁和读写锁,耗时有明显的减少!
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  • 原文地址:https://www.cnblogs.com/ten951/p/6212139.html
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