面试题：请编写一个Singleton程序

盖房子的图纸：单例设计模式，大概率面试题

class Singleton
{
    private static final Singleton INSTANCE = new Singleton() ;
    private Singleton() {} //构造方法私有化
    public static Singleton getInstance() {
        return INSTANCE ;

    }
    public void print() {
        System.out.println("Hello World !") ;

    }
}
public class TestDemo
{
    public static void main(String args[]) {
        Singleton s = Singleton.getInstance() ;
        s.print() ;

    }
}