java中的生产者和消费者的问题

1----使用Java.util.concurrent.locks包中的lock接口取代synchronized,通过ReentrantLock这个已经实现Lock接口的类,

创建ReentrantLock对象lock(private final ReentrantLock lock = new ReentrantLock(); ) ,并通过使用这个对象中的lock()方法让线程获得锁(lock.lock(););

使用unlock();在退出代码块块时释放锁(lock.unlock();),

2----其中while(flag)解决了if(flag)存在的重复生产,使得消费者丢失对其中被覆盖的数据(烧鸡)的读取.但是while会导致死锁,会出现全部线程都被休眠的情况,此时可以将notify ()修改为notifyAll()使得程序被全部唤醒,间接实现相互唤醒,但是由于对同类线程的唤醒时没有意义的,此时,程序的效率降低.

3---解决上一个问题的方法为:使用Java.util.concurrent.locks中的Condition接口,通过对同一个锁创建不同的Condition实例,并使用不同实例调用其各自的await()和signal()方法实现对t0 t1和t2 t3这2组线程的冻结和唤醒管理.从而不再需要每次都全部唤醒造成的效率降低的问题.

 /*
 需求:生产者---->消费者
 资源:烤鸭一只
      每生产一只,就消费一zhi
 */
 import java.util.concurrent.locks.*;
 class Resource
 {
     private String name;
     private int count=0;
     private boolean flag=false;
     private final ReentrantLock lock = new ReentrantLock();
     final Condition cond1  = lock.newCondition();
     final Condition cond2  = lock.newCondition();
     public  void make(String name)
     {
         lock.lock();
         while(flag)
             try
             {
                 cond1.await();
             }
             catch (InterruptedException e)
             {
             }

         this.name = name;
         count++;
         flag=true;
         cond2.signal();
         System.out.println(Thread.currentThread().getName()+"生产者..."+name+count);
         lock.unlock();
     }
     public void out()
     {
         lock.lock();
         while(!flag)
             try
             {
                 cond2.await();
             }
             catch (InterruptedException e)
             {
             }
         System.out.println(Thread.currentThread().getName()+"消费者......."+count);
         flag = false;
         cond1.signal();
         lock.unlock();
     }

 }
 class Producer implements Runnable
 {
     Resource r = new Resource();
     Producer(Resource r)
     {
         this.r = r;
     }
     public void run()
     {
         while(true)
         r.make("烤鸭");
     }
 }
 class Customer implements Runnable
 {
     Resource r = new Resource();
     Customer(Resource r)
     {
         this.r = r;
     }
     public void run()
     {
         while(true)
         r.out();
     }
 }
 class ProducerCustomer
 {
     public static void main(String[] args)
     {
         //建立资源类
          Resource r = new Resource();
         //建立任务对象
         Producer pro = new Producer(r);
         Customer cus = new Customer(r);
         //建立线程
         Thread t0 = new Thread(pro);
         Thread t1 = new Thread(pro);
         Thread t2 = new Thread(cus);
         Thread t3 = new Thread(cus);
         //开启线程
         t0.start();
         t1.start();
         t2.start();
         t3.start();

     }
 }