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();

    }
}