Java NIO - Condition

Condition用来实现对应Object的wati，notify，notifyAll三个方法。

在Condition中用await()替换wait()，用signal()替换notify() ，用signalAll()替换notifyAll()，传统线程之间的通讯Condition都可以实现。如下列子，我们实现一个读写操作，分为读写线程。

   
   
   
   

    
    
    
    
package chp3.condition;
    
    
    
    

    
    
    
    
import java.util.concurrent.locks.Condition;
    
    
    
    
import java.util.concurrent.locks.Lock;
    
    
    
    
import java.util.concurrent.locks.ReentrantLock;
    
    
    
    

    
    
    
    
public class BufferThread {
    
    
    
    

    
    
    
    
 final Lock lock = new ReentrantLock();// 锁
    
    
    
    
 final Condition notFull = lock.newCondition();// 写线程条件
    
    
    
    
 final Condition notEmpty = lock.newCondition();// 读线程条件
    
    
    
    

    
    
    
    
 final Object[] items = new Object[10];// 缓存队列
    
    
    
    

    
    
    
    
 int putptr/* 写索引 */, takeptr/* 读索引 */, count/* 队列中存在的数据个数 */;
    
    
    
    

    
    
    
    
 public void put(Object x) throws InterruptedException {
    
    
    
    
 lock.lock();
    
    
    
    
 try {
    
    
    
    
 while (count == items.length) {
    
    
    
    
 notFull.await();// 阻塞写线程
    
    
    
    
 }
    
    
    
    
 System.out.println("写入操作: index =  " + putptr + " value = " + x);
    
    
    
    
 items[putptr++] = x;
    
    
    
    
 if (putptr == items.length)
    
    
    
    
 putptr = 0;// 如果写索引写到队列的最后一个位置了，那么置为0
    
    
    
    
 ++count;// 个数++
    
    
    
    
 notEmpty.signal();// 唤醒读线程
    
    
    
    
 } finally {
    
    
    
    
 lock.unlock();
    
    
    
    
 }
    
    
    
    
 }
    
    
    
    

    
    
    
    
 public Object take() throws InterruptedException {
    
    
    
    
 lock.lock();
    
    
    
    
 try {
    
    
    
    
 while (count == 0)
    
    
    
    
 // 如果队列为空
    
    
    
    
 notEmpty.await();// 阻塞读线程
    
    
    
    
 Object x = items[takeptr];// 取值
    
    
    
    
 System.out.println("读取操作: index =" + takeptr + " vale = " + x);
    
    
    
    
 if (++takeptr == items.length)
    
    
    
    
 takeptr = 0;// 如果读索引读到队列的最后一个位置了，那么置为0
    
    
    
    
 --count;// 个数--
    
    
    
    
 notFull.signal();// 唤醒写线程
    
    
    
    
 return x;
    
    
    
    
 } finally {
    
    
    
    
 lock.unlock();
    
    
    
    
 }
    
    
    
    
 }
    
    
    
    

    
    
    
    
 public static void main(String[] args) {
    
    
    
    

    
    
    
    
 final BufferThread bt = new BufferThread();
    
    
    
    

    
    
    
    
 Thread t1 = new Thread(new Runnable() {
    
    
    
    

    
    
    
    
 @Override
    
    
    
    
 public void run() {
    
    
    
    
 for (int i = 0; i < 250; i++)
    
    
    
    
 try {
    
    
    
    
 bt.put(i);
    
    
    
    
 } catch (InterruptedException e) {
    
    
    
    
 e.printStackTrace();
    
    
    
    
 }
    
    
    
    
 }
    
    
    
    
 });
    
    
    
    

    
    
    
    
 Thread t2 = new Thread(new Runnable() {
    
    
    
    

    
    
    
    
 @Override
    
    
    
    
 public void run() {
    
    
    
    
 for (int i = 0; i < 230; i++)
    
    
    
    
 try {
    
    
    
    
 bt.take();
    
    
    
    
 } catch (InterruptedException e) {
    
    
    
    
 e.printStackTrace();
    
    
    
    
 }
    
    
    
    
 }
    
    
    
    
 });
    
    
    
    

    
    
    
    
 t1.start();
    
    
    
    
 t2.start();
    
    
    
    
 }
    
    
    
    
}
   
   
   
   

参考：http://blog.csdn.net/ghsau/article/details/7481142