JDK并发包---(8)ReadWriteLock读写锁：替换ReentrantLock，提高性能

import java.util.Date;
import java.util.Random;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import javax.annotation.PreDestroy;

public class ReadWriteLockDemo {

private static Lock lock = new ReentrantLock();
private static ReentrantReadWriteLock reentrantReadWriteLock = new ReentrantReadWriteLock();
private static Lock readLock = reentrantReadWriteLock.readLock();
private static Lock writeLock = reentrantReadWriteLock.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，ReadWriteLock的优势就越明显
return value;
} finally {
lock.unlock();
}
}

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

public static void main(String args[]) {
final ReadWriteLockDemo demo = new ReadWriteLockDemo();

Runnable readRunnable = new Runnable() {
@Override
public void run() {
try {
demo.handleRead(readLock);
// demo.handleRead(lock);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Read Thread End " + Thread.currentThread().getName() + ":" + new Date());
}

};

Runnable writeRunnable = new Runnable() {
@Override
public void run() {
try {
demo.handleWrite(writeLock, new Random().nextInt());
// demo.handleWrite(lock, new Random().nextInt());
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Write Thread End " + Thread.currentThread().getName() + ":" + new Date());
}

};

System.out.println("Starting:" + new Date());
for (int i = 0; i < 18; i++) {
new Thread(readRunnable).start();
}

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

}

}