import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class Data {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
public synchronized void set(){
System.out.println(Thread.currentThread().hashCode() + "set:begin" + sdf.format(new Date()));
try{
Thread.sleep(5000);
}catch(Exception e){
}finally{
System.out.println(Thread.currentThread().hashCode() + "set:end" +sdf.format(new Date()));
}
}
public synchronized void get(){
System.out.println(Thread.currentThread().hashCode() + "set:begin" + sdf.format(new Date()));
try{
Thread.sleep(5000);
}catch(Exception e){
}finally{
System.out.println(Thread.currentThread().hashCode() + "set:end" +sdf.format(new Date()));
}
}
}
public class Worker extends Thread {
Data data;
boolean read;
public Worker(Data data, boolean read) {
this.data = data;
this.read = read;
}
public void run() {
if (read)
data.get();
else
data.set();
}
}
public class ReadWriteLockDemo {
public static void main(String args[]) {
Data data = new Data();
Worker thread1 = new Worker(data, true);
Worker thread2 = new Worker(data, true);
thread1.start();
thread2.start();
}
}
上面的代码使用synchronized锁，用synchronized修饰的方法只能同时被一个线程访问，于是代码中两个线程要依次执行，结果如下
8637543set:begin2015-03-22 10:35:26
8637543set:end2015-03-22 10:35:31
22474382set:begin2015-03-22 10:35:31
22474382set:end2015-03-22 10:35:36
下面使用读写锁，只需要修改Data类就可以了
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class Data {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
ReadWriteLock lock = new ReentrantReadWriteLock();
Lock read = lock.readLock();
Lock write = lock.writeLock();
public void set(){
write.lock();
System.out.println(Thread.currentThread().hashCode() + "set:begin" + sdf.format(new Date()));
try{
Thread.sleep(5000);
}catch(Exception e){
}finally{
System.out.println(Thread.currentThread().hashCode() + "set:end" +sdf.format(new Date()));
write.unlock();
}
}
public void get(){
read.lock()
System.out.println(Thread.currentThread().hashCode() + "set:begin" + sdf.format(new Date()));
try{
Thread.sleep(5000);
}catch(Exception e){
}finally{
System.out.println(Thread.currentThread().hashCode() + "set:end" +sdf.format(new Date()));
read.unlock()
}
}
}
同时读，结果
30771886set:begin2015-03-22 10:51:18
14718739set:begin2015-03-22 10:51:18
30771886set:end2015-03-22 10:51:23
14718739set:end2015-03-22 10:51:23
两个线程同时读取数据，同时执行结束，没有限制。
public class ReadWriteLockDemo {
public static void main(String args[]) {
Data data = new Data();
Worker thread1 = new Worker(data, false);
Worker thread2 = new Worker(data, true);
thread1.start();
thread2.start();
}
}
第一个线程写， 第二个线程读
8637543set:begin2015-03-22 10:54:11
8637543set:end2015-03-22 10:54:16
4699264set:begin2015-03-22 10:54:16
4699264set:end2015-03-22 10:54:21
读写锁允许同时读，但不允许读写同时进行
原文：http://www.cnblogs.com/wuxinliulei/p/4356830.html