Re: Object orientation question
On 10/28/2014 8:29 AM, Eric Sosman wrote:
On 10/28/2014 5:45 AM, Andreas Leitgeb wrote:
Robert Klemme <shortcutter@googlemail.com> wrote:
On 27.10.2014 21:51, Eric Sosman wrote:
Clearly, the generated code is the same: AdditionInterface
extends
BaseInterface, therefore any class implementing AdditionInterface also
necessarily implements BaseInterface. If the class fails to provide a
method specified by BaseInterface, the code won't compile. So the
question is purely about readability and style.
This is not fully correct: if you check with reflection you will see
that there is a difference in what Class.getInterfaces() returns.
You don't even need reflection to notice a difference:
interface A { ... } | interface A { ... }
interface B { ... } | interface B extends A { ... }
class C implements A,B { ... } | class C implements B { ... }
... | ...
B foo = new C(); | B foo = new C();
A bar = foo; // barf! | A bar = foo; // ok
Instead of the second assignment you could have a call to a
method that takes an A and gets passed B-typed reference foo.
My Java compiler (Oracle's 1.8.0_20 on 64-bit Windows 7)
doesn't "barf" as you report. Has something changed? Are you
using a different javac? Here's the code; I've fleshed out
the ellipses and changed one name:
[...]
Ah, but I mis-read your post! On the left you have A and B as
completely independent interfaces, whereas on the right one is a
sub-interface of the other. The O.P. wrote (emphasis mine)
We have an interface called BaseIface and then we have a
BaseImpl. Then we have AddtionInterface and AdditionImpl.
*AdditionInterface is a BaseInterface.*
.... so your left-hand case is different from the situation he
asked about, and which I was addressing. Sorry for the confusion.
--
esosman@comcast-dot-net.invalid