The two doSomething() methods take different kinds of arguments -- they have different signatures -- so they're not polymorphic, they're overloads. The compiler chooses one at compile time based on the argument list and reference type.
If you change MySuperclass.doSomething() to accept a String argument, you'll see the polymorphic behavior you're expecting!
Got that. (That's why I added in the doSomethingElse() method.) And you're right, this isn't truly a polymorphism question.
But why would the compiler choose MySuperclass.doSomething()? I would expect that because the underlying object is actually an instance of MySubclass, the called method would be MySubclass.doSomething(). On top of that, the call in main() has a String argument, which would match MySubclass.doSomething(String) method more specifically than MySuperclass.doSomething(Object).
I'm sure I'm thinking about this incorrectly...but I still don't see it.
Joined: Dec 29, 2004
Because when overloading the method is chose at compile time based on the type of the reference, not the type of the object.
If you changed it to MySubclass name = new MySubclass();
you would get the subclass methods.
Joined: Jul 16, 2001
Got it; thanks! That explains the previous example, and it also explains why
MySubclass: doing something with an object MySubclass: doing something else
. The doSomething(Object) method is chosen at compile time because the reference is to a MySuperclass, but at run time the decision is made to use the subclass's doSomething(Object). Nasty...but now understandable.