读写锁的使用

package concurrent;

import java.util.Random;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;

/**
*1、readLock可重入;
*2、writeLock必须等待所有的readLock释放后才可进入;
*3、writeLock范围内,readLock不可进入
*/
public class ReadWriteLockTest {

private ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();

private ReadLock readLock = readWriteLock.readLock();

private WriteLock writeLock = readWriteLock.writeLock();

private String shareData = "寂寞等待中。。。";

public ReadWriteLockTest() {
}

public void write(String str) {
writeLock.lock();//可用tryLock()干点其他事
// if(!writeLock.tryLock()){
// System.err.println("读锁数量:"+readWriteLock.getReadLockCount());
// return;
// }
System.err.println("ThreadName:" + Thread.currentThread().getName() + " locking...");
try {
shareData = str;
System.err.println("ThreadName:" + Thread.currentThread().getName() + " 修改为:" + str);
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
System.err.println("ThreadName:" + Thread.currentThread().getName() + " unlock...");
writeLock.unlock();
}
}

public String read() {
readLock.lock();
System.out.println("ThreadName:" + Thread.currentThread().getName() + " lock...");
try {
System.out.println("ThreadName:" + Thread.currentThread().getName() + " 获取为:" + shareData);
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
readLock.unlock();
System.out.println("ThreadName:" + Thread.currentThread().getName() + " unlock...");
}
return shareData;
}

/**
* @param args
*/
public static void main(String[] args) {

final ReadWriteLockTest shareData = new ReadWriteLockTest();

for (int i = 0; i < 5; i++) {
new Thread(new Runnable() {

@Override
public void run() {
shareData.read();
}
}, "get Thread-" + i).start();
}

for (int i = 0; i < 10; i++) {
new Thread(new Runnable() {
@Override
public void run() {
shareData.write(new Random().nextLong() + "");
}
}, "write Thread-" + i).start();

}
}
}
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