一、簡介

有時候我們對資源的修改操作非常地少，但是讀取的頻率卻很高。如果采用一般的互斥鎖，那麽大量的讀取操作也需要做等待。基於讀寫分離的思想，我們可以使用JDK的讀寫鎖來處理這種情況。

1）讀讀不互斥；

2）讀寫互斥。

3）寫寫互斥

JDK文檔地址：http://tool.oschina.net/uploads/apidocs/jdk-zh/java/util/concurrent/locks/ReentrantReadWriteLock.html

二、代碼示例

import java.util.concurrent.locks.ReentrantReadWriteLock;

public
 
 class ReadWriteLockDemo {
    private static ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
    private static ReentrantReadWriteLock.ReadLock readLock = lock.readLock();
    private static ReentrantReadWriteLock.WriteLock writeLock = lock.writeLock();

    private static void read() {
        
 
for (int i = 0; i < 2; i++) {
            int finalI = i;
            new Thread(() -> {
                readLock.lock();
                try {
                    System.out.println("get read lock i=" + finalI);
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                readLock.unlock();
            }).start();
        }
    }

    
 
public static void write() {
        new Thread(() -> {
            writeLock.lock();
            System.out.println("get write lock");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            writeLock.unlock();
        }).start();
    }

    public static void main(String[] args) throws InterruptedException {
        write();
        read();
    }
}

十五、讀寫鎖