最好的单例模式

package test;

public class Singleton {
    
    Singleton(){
        System.out.println("**************");
    }
    
    public static Singleton Instance(){
        
        return Nested.instance;
    }
    
    public static void main(String[] args) {
        
        Singleton.Instance(); 
        Singleton.Instance(); 
        Singleton.Instance(); 
        Singleton.Instance(); 
        Singleton.Instance(); 
    }
}

class Nested{
    
    Nested(){
        
    }
    
    static Singleton instance = new Singleton();
}

结果：只输出一行 ************