标签：
推荐使用方法：
public static class Singleton{
private static final Singleton instance = new Singleton();
private Singleton(){
}
public static Singleton getInstance(){
return instance;
}
}
线程不安全：（加上synchronized也不够好）：
public static class Singleton{
private static Singleton instance = null;
private Singleton(){
}
public static Singleton getInstance(){
if(instance == null){
instance = new Singleton();
}
return instance;
}
}
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原文地址：http://www.cnblogs.com/wangqian-easy/p/4860474.html
