Delegate vs Callback in Java

Question

I have some misunderstanding about terms of delegates and callbacks in Java.

class MyDriver {

    public static void main(String[] argv){
        MyObject myOb         


        

Answer 1

I'd argue that "callback" is a name for a generic pattern where you provide the module you're calling with a a way for said module to call your code. A C# delegate, or an ObjC delegate object, (these two being entirely different beasts) or a Java class-implementing-the-callback-interface are different, platform-specific ways of implementing the callback pattern. (They can also themselves be considered patterns.) Other languages have more or less subtly different ways of doing so.

The above concept of "delegate" is also similar to the Strategy pattern, where the delegate can be thought of as one. Similarly, a Visitor is also a type of callback. (A visitor is also a strategy for processing each visited item.)

All this is using definitions that are intuitive to me, and might not be to anyone else, because neither "callback" or "delegate" are formal terms and it makes little sense to discuss them without referring to a previous definition thereof that's valid in your context. Consequently it makes little sense to ask what the definition is since, to the best of my knowledge, there isn't an authoritative one. To wit, the fact that other answers to this question are likely to say something entirely different.

My recommendation would be to focus on the merits of your design – whether it achieves what you need, doesn't introduce tight coupling, etc. – rather than on minutiae of semantics. When two design patterns appear similar, they probably can be used to achieve similar goals equally well.