Does interfaces effect performance because of reducing dependencies in Java Compiler or Eclipse?

Question

Assume two different scenarios:

• a) Each (service) class X has an interface X and exactly one implemntation XImpl. Every other (service) class (for example YImpl) always interacts with other (service) classes through there interface (X), but never directly refer to the implementation class (XImpl) -- This is at least a very common pattern.
• b) Just like a) but without all the interfaces. There is only XImpl and YImpl it refers directly to YImpl.

(I guess I know a lot of the purposes of a) and b), so please do not discuss that here.)

My Question is: Does variant b) has a negative performance effect when working with Eclipse, Maven and M2E 1.0?

I can imagine this, because I you have way a) and you editing something in XImpl it does not effect YImpl because they are completely decoupled by interface X. But when removing the interfaces in b) so they are not longer decoupled.

Answer 1

You don't want to sacrifice the design of your application to gain 2 micro-seconds each time Eclipse or Maven compiles your classes. BTW, if you edit XImpl, it has to check that it still respects the contract of the X interface which is used by YImpl, so it probably doesn't make any difference.