1/9     Alright, so why does Java have both "abstract" and "interface"?
        Isn't that redundant?
        \_ Java is doomed.  Don't get too into it.
        \_ no. interfaces can't contain implementation.  train harder.
           \_ you too must train harder.  abstract methods also don't
              contain implementation.  train even harder.
              \_ if you think the q refers to the method qualifier, you suck.
              \_ you also must train harder. you can have 1 method abstract and
                 implement other methods still making the entire class abstract
                 which means you can't instantiate it. Interfaces require
                 all methods abstract and thus no implementation at all.
        \_ abstract modifies classes.  it's useful if you want to
           extend a superclass that does have some methods predefined,
           in addition to some undefined/abstract methods.
           whereas, interfaces cannot have any methods predefined.
           Or, you only partially implement an interface, leaving some
           methods undefined.
        \_ And now, finally, the right answer: in Java, you can not have
           multiple superclasses (abstract or not), but you can have
           several superinterfaces.  Interfaces are Java's way of doing
           multiple inheritance while avoiding the virtual base class
           mess of C++.  There are problems with Java's approach, but
           it works most of the time.
           \_ this is factually correct but is not the right answer because
              it does not address the question.  the other reponses do.  dork.
              \_ Well...  How do the previous responses address the difference
                 between abstract class foo { abstract int bar(); } and
                 interface foo { int bar(); } ?  Multiple inheritance
                 is the *only* thing that you can do with interfaces and
                 can't do with abstract classes -- therefore the only reason
                 "interface" is not redundant.  So either you have no clue or
                 you are a dork -- pick at least one.
              \_ Who cares?  It's a still-born language.
                \_right, with hundred of millions of dollars of engineering
                efforts using it. by comparison, you're stillborn.
                 \_ "Everyone else is using Win95 so it must be good!"
                        \_it's an argument proving it's not stillborn,
                        not that it's a good language. (which it is,
                        for some purposes)
        \_ why can't motd posters use intelligent, logical rhetoric instead of
           meaningless personal attacks? dumb fucks.
           \_ shut up, ilya.