Thread: Why use interfaces? I'm not grasping this concept.

Ok, I'm relatively new to Java. I'm getting a pretty good grasp of most of the foundations, but interfaces just baffle me. If you have to define all the methods later on anyway, what's the point of using the interface?

I'm sure eventually I would get this after a lot more study, but I'd really like to generally understand the concept.

It's explained in various teaching materials that if you implement an interface, all the methods must be defined in the class or you will have a compile error. So the one possibility I'm thinking of is this... Is the purpose just to make sure that another coder doesn't forget to utilize a certain method? I'll use a gaming example because eventually that's what I'd like to get into.

A character in a game HAS TO have a style of walking, a voice, a certain set of weapons, etc etc... so the interface guarantees that another coder working on that character won't forget to code in certain aspects of the character? Maybe I'm way off. Any insight would be appreciated. Thanks!

A character in a game HAS TO have a style of walking, a voice, a certain set of weapons, etc etc... so the interface guarantees that another coder working on that character won't forget to code in certain aspects of the character?

I think this is it.

And it's not just forgetfulness on the part of 2nd-programmer that you want to guard against. You might want to write code that does a die(Character character). It will invoke the walking's stop() method, empty the weapons set, and make the voice utter something dramatic. You can write this code even before 2nd-programmer has implemented the Character interface. That's because the Character definition defines what you expect a character to be able to do and the compiler will enforce this for any programmer who says "import com.coolgame.Character;"

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This reliance on the compiler to enforce your types into the future and unknown (aka "strong typing") is Java's way of doing it. Other languages - think JavaScript - aren't so compiler reliant. So long as a JS Object instance has a weapons, a voice and walks you could pass it to die().

Originally Posted by zeropointfield

A character in a game HAS TO have a style of walking, a voice, a certain set of weapons, etc etc... so the interface guarantees that another coder working on that character won't forget to code in certain aspects of the character?

The guarantee is not that the character will have a voice, so to speak. The implementing class could just have an empty bodied method, basically ignoring what you considered an important role for a character. Perhaps a "blob" would have a style of walking and weapons, but no voice after all. The blob would still have to include the voice method, even if it is blank. The guarantee is that if some code asks the blob to speak, the blob can effectively ignore the request without causing the game to crash.