读写锁：ReadWriteLock

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(); // 模拟读操作
			Thread.sleep(1000); // 读操作的耗时越多，读写锁的优势就越明显
			return value;
		} finally {
			lock.unlock();
		}
	}

	public void handleWrite(Lock lock, int index) throws InterruptedException {
		try {
			lock.lock();
			Thread.sleep(1000);
			value = index;
		} finally {
			lock.unlock();
		}
	}

	public static void main(String[] args) {
		final ReadWriteLockDemo demo = new ReadWriteLockDemo();
		Runnable readRunnale = new Runnable() {
			@Override
			public void run() {
				try {
					demo.handleRead(readLock);
//					demo.handleRead(lock);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		};
		Runnable writeRunnale = new Runnable() {
			@Override
			public void run() {
				try {
					demo.handleWrite(writeLock, new Random().nextInt());
//					demo.handleWrite(lock, new Random().nextInt());
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		};

		for (int i = 0; i < 18; i++) {
			new Thread(readRunnale).start();
		}

		for (int i = 18; i < 20; i++) {
			new Thread(writeRunnale).start();
		}

	}

}