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.

 1 /*
 2 需求:生产者---->消费者
 3 资源:烤鸭一只
 4      每生产一只,就消费一zhi
 5 */
 6 import java.util.concurrent.locks.*;
 7 class Resource
 8 {
 9     private String name;
10     private int count=0;
11     private boolean flag=false;
12     private final ReentrantLock lock = new ReentrantLock();
13     final Condition cond1  = lock.newCondition();
14     final Condition cond2  = lock.newCondition();
15     public  void make(String name)
16     {
17         lock.lock();
18         while(flag)
19             try
20             {
21                 cond1.await();
22             }
23             catch (InterruptedException e)
24             {
25             }
26
27         this.name = name;
28         count++;
29         flag=true;
30         cond2.signal();
31         System.out.println(Thread.currentThread().getName()+"生产者..."+name+count);
32         lock.unlock();
33     }
34     public void out()
35     {
36         lock.lock();
37         while(!flag)
38             try
39             {
40                 cond2.await();
41             }
42             catch (InterruptedException e)
43             {
44             }
45         System.out.println(Thread.currentThread().getName()+"消费者......."+count);
46         flag = false;
47         cond1.signal();
48         lock.unlock();
49     }
50
51 }
52 class Producer implements Runnable
53 {
54     Resource r = new Resource();
55     Producer(Resource r)
56     {
57         this.r = r;
58     }
59     public void run()
60     {
61         while(true)
62         r.make("烤鸭");
63     }
64 }
65 class Customer implements Runnable
66 {
67     Resource r = new Resource();
68     Customer(Resource r)
69     {
70         this.r = r;
71     }
72     public void run()
73     {
74         while(true)
75         r.out();
76     }
77 }
78 class ProducerCustomer
79 {
80     public static void main(String[] args)
81     {
82         //建立资源类
83          Resource r = new Resource();
84         //建立任务对象
85         Producer pro = new Producer(r);
86         Customer cus = new Customer(r);
87         //建立线程
88         Thread t0 = new Thread(pro);
89         Thread t1 = new Thread(pro);
90         Thread t2 = new Thread(cus);
91         Thread t3 = new Thread(cus);
92         //开启线程
93         t0.start();
94         t1.start();
95         t2.start();
96         t3.start();
97
98     }
99 }