单例模式

public class main {
    static public void main(String[] a){
        only_one k=only_one.get();
        k.mess();
    }
}

public class only_one {
    static private only_one onlyOne=new only_one();
    private only_one(){}

    public static only_one get(){
        return onlyOne;
    }

    public void mess(){
        System.out.println("成功");
    }
}