Condition 将 Object的通信方法（wait、notify 和 notifyAll）分解成截然不同的对象，用await()替换wait()，用signal()替换notify()，用signalAll()替换notifyAll()，传统线程的通信方式，Condition都可以实现，这里注意，Condition是被绑定到Lock上的，要创建一个Lock的Condition必须用newCondition()方法。

Condition的强大之处在于它可以为多个线程间建立不同的Condition， 使用synchronized/wait()只有一个阻塞队列，notifyAll会唤起所有阻塞队列下的线程，而使用lock/condition，可以实现多个阻塞队列，signalAll只会唤起某个阻塞队列下的阻塞线程。

- 使用synchronized/wait()实现生产者消费者模式如下：

//模拟生产和消费的对象    class Buffer {        private int maxSize; private List
    
      storage; Buffer(int size){ maxSize=size; storage=new LinkedList<>(); } //生产方法 public synchronized void put() { try { while (storage.size() ==maxSize ){ //如果队列满了 System.out.print(Thread.currentThread().getName()+": wait \n");; wait();//阻塞线程 } storage.add(new Date()); System.out.print(Thread.currentThread().getName()+": put:"+storage.size()+ "\n"); Thread.sleep(1000); notifyAll();//唤起线程 } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } //消费方法 public synchronized void take() { try { while (storage.size() ==0 ){ //如果队列满了 System.out.print(Thread.currentThread().getName()+": wait \n");; wait();//阻塞线程 } Date d=((LinkedList
     
      )storage).poll(); System.out.print(Thread.currentThread().getName()+": take:"+storage.size()+ "\n"); Thread.sleep(1000); notifyAll();//唤起线程 } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } //生产者 class Producer implements Runnable{ private Buffer buffer; Producer(Buffer b){ buffer=b; } @Override public void run() { while(true){ buffer.put(); } } } //消费者 class Consumer implements Runnable{ private Buffer buffer; Consumer(Buffer b){ buffer=b; } @Override public void run() { while(true){ buffer.take(); } } } // public class Main{ public static void main(String[] arg){ Buffer buffer=new Buffer(10); Producer producer=new Producer(buffer); Consumer consumer=new Consumer(buffer); //创建线程执行生产和消费 for(int i=0;i<3;i++){ new Thread(producer,"producer-"+i).start(); } for(int i=0;i<3;i++){ new Thread(consumer,"consumer-"+i).start(); } } }
     
    

 

- 使用lock/condition实现生产者消费者模式如下：

import java.util.Date;import java.util.LinkedList;import java.util.List;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;class Buffer {    private  final Lock lock;    private  final Condition notFull;    private  final Condition notEmpty;    private int maxSize; private List
    
      storage; Buffer(int size){ //使用锁lock，并且创建两个condition，相当于两个阻塞队列 lock=new ReentrantLock(); notFull=lock.newCondition(); notEmpty=lock.newCondition(); maxSize=size; storage=new LinkedList<>(); } public void put() { lock.lock(); try { while (storage.size() ==maxSize ){ //如果队列满了 System.out.print(Thread.currentThread().getName()+": wait \n");; notFull.await();//阻塞生产线程 } storage.add(new Date()); System.out.print(Thread.currentThread().getName()+": put:"+storage.size()+ "\n"); Thread.sleep(1000); notEmpty.signalAll();//唤醒消费线程 } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ lock.unlock(); } } public void take() { lock.lock(); try { while (storage.size() ==0 ){ //如果队列满了 System.out.print(Thread.currentThread().getName()+": wait \n");; notEmpty.await();//阻塞消费线程 } Date d=((LinkedList
     
      )storage).poll(); System.out.print(Thread.currentThread().getName()+": take:"+storage.size()+ "\n"); Thread.sleep(1000); notFull.signalAll();//唤醒生产线程 } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ lock.unlock(); } } } class Producer implements Runnable{ private Buffer buffer; Producer(Buffer b){ buffer=b; } @Override public void run() { while(true){ buffer.put(); } } } class Consumer implements Runnable{ private Buffer buffer; Consumer(Buffer b){ buffer=b; } @Override public void run() { while(true){ buffer.take(); } } } public class Main{ public static void main(String[] arg){ Buffer buffer=new Buffer(10); Producer producer=new Producer(buffer); Consumer consumer=new Consumer(buffer); for(int i=0;i<3;i++){ new Thread(producer,"producer-"+i).start(); } for(int i=0;i<3;i++){ new Thread(consumer,"consumer-"+i).start(); } } }