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Singleton is a most widely used design pattern. If a class has and only has one instance at every moment, we call this design as singleton. For example, for class Mouse (not a animal mouse), we should design it in singleton.
You job is to implement a getInstance method for given class, return the same instance of this class every time you call this method.
In Java:
A a = A.getInstance();
A b = A.getInstance();
a should equal to b.
If we call getInstance concurrently, can you make sure your code could run correctly?
class Solution { /** * @return: The same instance of this class every time
/*Singleton类定义一个GetInstance()操作，允许客户访问它的唯一实例。GetInstance()是一个静态方法，主要负责创建自己的唯一实例。*/ */ private static Solution singleton;
//构造方法让其private，这就堵死了外界利用new创建此类实例的可能// private Solution(){};
/*此方法是获得本类实例的唯一全局访问点。*/ public static Solution getInstance() { // /*若实例不存在，则new一个新实例，否则返回已有实例*/ if(singleton==null) { singleton=new Solution(); } return singleton; } };
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原文地址：http://www.cnblogs.com/kittyamin/p/5134887.html
