JUC之ReadWriteLock的简介与使用_juc readock

1.ReadWriteLock简介

2. ReadWriteLock应用

package rw;
 
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
 
/**
 * 
 * 独占锁（写锁）：一次只能被一个线程占用
 * 共享锁（读锁）：多个线程可以同时占有
 * 
 * ReadWriteLock
 * 读，读可以共存
 * 读，写不可共存
 * 写，写不可共存
 * @author Admin
 *
 */
public class ReadWriteLockDemo {
 
	public static void main(String[] args) {
//		MyCache myCacheLock = new MyCache();
		MyCacheLock myCacheLock = new MyCacheLock();
 
//		写入
		for (int i = 1; i <= 5; i++) {
			final int temp = i;
			new Thread(() -> {
				myCacheLock.put(temp + "", temp + "");
			},String.valueOf(i)).start();
		}
 
//		读取
		for (int i = 1; i <= 5; i++) {
			final int temp = i;
			new Thread(() -> {
				myCacheLock.get(temp + "");
			},String.valueOf(i)).start();
		}
	}
}
 
class MyCacheLock {
	private volatile Map<String, Object> map = new HashMap<>();
//	读写锁，更加细粒度的控制
	private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
 
//	存，写，只能一个线程进入
	public void put(String key, Object value) {
		readWriteLock.writeLock().lock();
		try {
			System.out.println(Thread.currentThread().getName() + "写入" + key);
			map.put(key, value);
			System.out.println(Thread.currentThread().getName() + "写入ok");
		} finally {
			readWriteLock.writeLock().unlock();
		}
 
	}
 
//	取，读,所有人都可以读
	public void get(String key) {
		readWriteLock.readLock().lock();
		try {
			System.out.println(Thread.currentThread().getName() + "读取" + key);
			Object object = map.get(key);
			System.out.println(Thread.currentThread().getName() + "读取ok");
		} finally {
			readWriteLock.readLock().unlock();
		}
 
	}
}
 
//自定义缓存
class MyCache {
	private volatile Map<String, Object> map = new HashMap<>();
 
//	存，写
	public void put(String key, Object value) {
		System.out.println(Thread.currentThread().getName() + "写入" + key);
		map.put(key, value);
		System.out.println(Thread.currentThread().getName() + "写入ok");
	}
 
//	取，读
	public void get(String key) {
		System.out.println(Thread.currentThread().getName() + "读取" + key);
		Object object = map.get(key);
		System.out.println(Thread.currentThread().getName() + "读取ok");
	}
}

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