单例模式

 1 //饿汉式单例类.在类初始化时，已经自行实例化 
 2 public class Singleton{
 3     //默认构造
 4     private Singleton{}
 5     //已经自行实例化
 6     private static final Singleton singleton = new Singleton();
 7     //静态的工厂方法
 8     public static Singleton getSingleton{
 9         return singleton;
10     }
11 }

 1 //懒汉式单例类.在类初始化时，已经自行实例化 
 2 public class Singleton{
 3     //默认构造
 4     private Singleton{}
 5     //已经自行实例化
 6     private static final Singleton singleton = null;
 7     //静态的工厂方法
 8     public static Singleton getSingleton{
 9         if(singleton != null){
10             singleton = new Singleton();
11         }
12         return singleton
13     }
14 }