import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * 读写锁
 * @author tonfay
 * 
 * 多线程同时读一个资源类没有问题
 * 只允许一个线程写
 *
 */
public class ReadWriteLockDemo {
	Map<String,Object> cache = new HashMap<String, Object>();
	
	public static void main(String[] args) {
		Cache cache = new Cache();
		
		for(int i =1;i<=5;i++) {
			final int tempi = i;
			new Thread(new Runnable() {
				@Override
				public void run() {
					cache.put(tempi+"", tempi+"");
				}
			}).start();
		}
		
		
		for(int i =1;i<=5;i++) {
			final int tempi = i;
			new Thread(new Runnable() {
				@Override
				public void run() {
					cache.get(tempi+"");
				}
			}).start();
		}
	}
}

class Cache{
	private volatile Map<String, Object> cache = new HashMap<String, Object>();
	ReentrantReadWriteLock rrwlock = new ReentrantReadWriteLock();
	
	public void put(String key ,Object value) {
		try {
			rrwlock.writeLock().lock();
			System.out.println(Thread.currentThread().getName() + "\t 开始put");
			cache.put(key, value);
			try {TimeUnit.MILLISECONDS.sleep(300);} catch (InterruptedException e) {e.printStackTrace();}
			System.out.println(Thread.currentThread().getName() + "\t put成功");
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			rrwlock.writeLock().unlock();
		}
	}
	
	public void get(String key) {
		try {
			rrwlock.readLock().lock();
			System.out.println(Thread.currentThread().getName() + "\t 开始get");
			Object res = cache.get(key);
			try {TimeUnit.MILLISECONDS.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}
			System.out.println(Thread.currentThread().getName() + "\t get成功->"+ res);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			rrwlock.readLock().unlock();
		}
	}
}