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