单例的实现--静态内部类

 1 package com.redis.threadpool;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 import java.util.concurrent.ArrayBlockingQueue;
 6 import java.util.concurrent.ExecutorService;
 7 import java.util.concurrent.Executors;
 8 
 9 /**
10  * @Author zhangliwei
11  * @Date 2018/11/13 下午3:39
12  * 单例的实现有很多种
13  * 静态内部类的方式，绝对线程安全的
14  */
15 public class RequestProcessThreadPool {
16 
17     private ExecutorService threadPool = Executors.newFixedThreadPool(10);
18     /**
19      * 内存队列
20      */
21     private List<ArrayBlockingQueue<Request>> queues = new ArrayList<>();
22 
23     public RequestProcessThreadPool() {
24         for (int i = 0; i < 10; i++) {
25             ArrayBlockingQueue<Request> arrayBlockingQueue = new ArrayBlockingQueue<>(100);
26             queues.add(arrayBlockingQueue);
27             threadPool.submit(new WorkerThread(queues));
28 
29         }
30     }
31 
32     /**
33      * 单例的实现有很多种
34      * 静态内部类的方式，绝对线程安全的
35      */
36     private static class Singleton{
37 
38         private static RequestProcessThreadPool instance;
39 
40         static {
41             instance = new RequestProcessThreadPool();
42         }
43 
44         public static RequestProcessThreadPool getInstance(){
45 
46             return instance;
47         }
48     }
49 
50     /**
51      * jvm的机制去保证多线程并发安全
52      * 静态内部类的方式，去初始化单例
53      * @return
54      */
55     public static RequestProcessThreadPool getInstance(){
56         return Singleton.getInstance();
57     }
58 
59     public void init(){
60         getInstance();
61     }
62 
63 }

 1 package com.imooc.schoolproject.zookeeper;
 2 
 3 /**
 4  * @Author zhangliwei
 5  * @Date 2018/11/20 下午8:22
 6  * 单例模式获取zookeeper
 7  */
 8 public class ZookeeperSession {
 9 
10     public static class Singleton{
11         
12         private static ZookeeperSession singleton;
13 
14         static {
15             singleton = new ZookeeperSession();
16         }
17 
18         public static ZookeeperSession getInstance(){
19             return singleton;
20         }
21     }
22 
23     public static ZookeeperSession getZookeeperInstance(){
24         return Singleton.getInstance();
25     }
26 
27     public static void init(){
28         getZookeeperInstance();
29     }
30 }