JDK5.0新特性系列---11.4线程 Condition

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import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock; /** *有时候线程取得lock后需要在一定条件下才能做某些工作，比如经典的Producer和Consumer问题 *在Java 5.0以前，这种功能是由Object类的wait(),notify()和notifyAll()等方法实现的 *在5.0里面，这些功能集中到了Condition这个接口实现 *//** * 使用Condition的关键技术点如下: * 1.通过Lock的newCondition方法创建Condition的对象 * 2.Condition的await方法使当前线程进入等待状态,并且释放它占据的Lock,直到有其他的线程唤醒当前线程时,重新占有Lock. * 3.Condition的signal方法唤醒其他正在等待该Condition的线程. */public class ConditionTest {    /**     * 篮子程序，这里为了简化问题，篮子中最多只能有一个苹果     * Consumer必须在篮子里有苹果的时候才能吃苹果，否则它必须暂时放弃对篮子的锁定     * 等到Producer往篮子里放了苹果后再去拿来吃。     * 否则它也需要暂时解锁等Comsumer把苹果吃了才能往篮子里放苹果。     */    public static class Basket{        //锁        Lock lock = new ReentrantLock();        //根据锁产生Condition对象        Condition produced = lock.newCondition();        Condition consumed  = lock.newCondition();        //篮子里的苹果数，最多为1        int num = 0;        //生产苹果，往篮子里放        public void produce() throws InterruptedException{            //获得锁            lock.lock();            System.out.println("Producer get a lock...");                      try{                //判断是否满足生产条件                while(num == 1){                    //如果有苹果，则不生产，放弃锁，进入睡眠                    //等待消费者消费                    System.out.println("Producer sleep...");                    consumed.await();                    System.out.println("Producer awaked...");                }                //生产苹果                Thread.sleep(500);                System.out.println("Producer produced an Apple.");                num = 1;                //通知等待produced Condition的线程                produced.signal();            }finally{                lock.unlock();            }        }        //消费苹果，从篮子里取        public void consume() throws InterruptedException{            //获得锁            lock.lock();            System.out.println("Consumer get a lock...");            try{                //判断是否满足消费条件                while(num == 0){                    //如果没有苹果，无法消费，则放弃锁，进入睡眠                    //等待生产者生产苹果                    System.out.println("Consumer sleep...");                    produced.await();                    System.out.println("Consumer awaked...");                }                //吃苹果                Thread.sleep(500);                System.out.println("Consumer consumed an Apple.");                num = 0;                //发信号唤醒某个等待consumed Condition的线程                            consumed.signal();            } finally {                lock.unlock();            }        }    }    //测试Basket程序    public static void testBasket() throws Exception{        final Basket basket = new Basket();        //定义一个producer        Runnable producer  = new Runnable(){            public void run() {                try{                    basket.produce();                }catch(InterruptedException ex){                    ex.printStackTrace();                }            }                   };        //定义一个consumer        Runnable consumer = new Runnable(){            public void run(){                try{                    basket.consume();                }catch(InterruptedException ex){                    ex.printStackTrace();                }            }        };        //各生产3个consumer和producer        ExecutorService service = Executors.newCachedThreadPool();        for(int i = 0; i <3; i++){            service.submit(producer);        }        for(int i = 0;i<3;i++){            service.submit(consumer);        }        service.shutdown();    }    public static void main(String... args)throws Exception{        ConditionTest.testBasket();    }}