Inheritance Variable assignment

[Tim-Ting Chang]

What happens when we assign a new subclass instance to a superclass variable identifier?

Specifically, what happens if I call subclass-only fields and methods from a superclass variable identifier?

e.g.

class SuperClass {
  public String myVar;
  SuperClass(String var) {
    myVar = var;
  }
  void add(String var) {
    myVar += var;
  }
}

class SubClass1 {
  public String myVar;
  SubClass(String var) {
    myVar = var;
  }
  void add(String var) {
    myVar += var;
  }
}

class SubClass2 {
  public String my Var;
  SubClass(String var) {
    myVar = var;
  }
  void add(String var) {
    myVar += var;
  }
}

class Test {
  static void main(String[] args) {
    SuperClass var0 = new SuperClass("Super");
    SuperClass var1 = new SubClass1("Sub1");
    SuperClass var2 = new SubClass2("Sub2");

    System.out.println(var1.myVar);
    System.out.println(var2.myVar);

    var1.add("more");
    var2.add("more");

    System.out.println(var0.myVar);  
    System.out.println(var1.myVar);
    System.out.println(var2.myVar);
}

What's the output of Test?

I want to know the rationale behind the output, that's why I asked here rather than compiling it.

[fred rosenberger]

why don't you try and figure out the output yourself, and then run it and see if you're. right. If so, AWESOME!!!.

If you're wrong, try and figure out WHY you're wrong.

If you can't figure out why you're wrong, come back and ask us why the output is different from what you expect (and please tell us what you expected, what you got, and WHY you thought what you did).

THAT'S going to be the best way for you to learn.

[Max Rahder]

(I don't want to circumvent anyone's learning experience, but...) Tim-Ting, your subclass declarations need to use the "extends" keyword. The way you've coded it, those classes are not subclassing SuperClass. Once you've done that, you can start exploring the question you raised.