如何输出引用变量中的内容

[qqq1352937294]

class Father extends Grandpa{
protected Father(){
System.out.println("default Father");
}
public Father(String GrandpaName,String FatherName){
super(GrandpaName);
System.out.println(FatherName);
}
}
class Son extends Father{
public Son(){
System.out.println("default Son");
}
public Son(String GrandpaName,String FatherName,String SonName){
super(GrandpaName,FatherName);
System.out.println(SonName);
}
public static void main(String[] args) {
Son s1 = new Son("My Grandpa","My Father","My Son");//输入 My Grandpa My Father My Son
Son s2 = new Son();//default Grandpa default Father default Son
}
}