Equivalent of #define in Java?
I'm writing a library that needs to have some code if a particular library is included. Since this code is scattered all around the project, it would be nice if users didn't have to comment/uncomment everything themselves.
In C, this would be easy enough with a #define in a header, and then code blocks surrounded with #ifdefs. Of course, Java doesn't have the C preprocessor...
To clarify - several external libraries will be distributed with mine. I do not want to have to include them all to minimize my executable size. If a developer does include a library, I need to be able to use it, and if not, then it can just be ignored.
What is the best way to do this in Java?
Answer
There's no way to do what you want from within Java. You could preprocess the Java source files, but that's outside the scope of Java.
Can you not abstract the differences and then vary the implementation?
Based on your clarification, it sounds like you might be able to create a factory method that will return either an object from one of the external libraries or a "stub" class whose functions will do what you would have done in the "not-available" conditional code.