What is the reasoning behind not allowing supertypes on Java method overrides?

Question

The following code is considered invalid by the compiler:

class Foo {
    void foo(String foo) { ... }
}

class Bar extends Foo {
    @Override
    void foo(Obje         


        

Answer 1

If you can override with superclasses, why not with subclasses as well?

Consider the following:

class Foo {
  void foo(String foo) { ... }
}

class Bar extends Foo {
  @Override
  void foo(Object foo) { ... }
}
class Another extends Bar {
  @Override
  void foo(Number foo) { ... }
}

Now you have succesfully overriden an method whose original parameter was a String to accept a Number. Inadvisable to say the least...

Instead, the intended results may be replicated by using overloading and the following, more explicit, code:

class Foo {
    void foo(String foo) { ... }
}

class Bar extends Foo {
    @Override
    private void foo(String foo) { ... }
    void foo(Object foo) { ... }
}
class Another extends Bar {
    @Override
    private void foo(Object foo) { ... }
    void foo(Number foo) { ... }
}