The problem with Java Generics is.... (Redux)

...while pair programming... bill > Hey, we could use generics here. bob > Great, why don't you drive. bill > Sure. What we need is a T here. Replace that return with T. Add another T here, and there you go. We can now use this for all types of things. Compile...check. Great. Let's fire up jetty. bob > Hey, what does that mean? bill > Strange...it compiled ok. Oh! No problem. What we need is to add a ? here, then extends that to type T and that should work. bob > Nope!! bill > Right, if move that ? to here, then use super of not extends, add T here that will work. bob > Sorry, still not happy. bill > Really? But that's it? You have a T, and ?, the word extends or super. Damn! bob > Why not use instanceof? bill > You can't because of erasure! bob > Erasure? The electronic group from the 80s....I kind of liked them. ♪I tried to discover...A little something to make me sweeter...♪ bill > Stop that!! bob > Sorry. bill > No, Type Erasure. When a generic type is instantiated, the compiler translates those types by a technique called type erasure — a process where the compiler removes all information related to type parameters and type arguments within a class or method. bob > Why would you do that? bill > Two words. Backwards compatibility. bob > That's doesn't help us. bill > Welcome to Generics in Java. bob > I knew we should have written this in Ruby!