Just a curious question. Clean and build take a few moments, at least. But how much code does the editor actually have to go through to do the build. It doesn't seem like it should be that much to be as slow as it is.
I received a duplicate answer flag, but the answer that was linked has to do with deleting an element from an array in C# and has nothing to do with my question.
It depends on a project but simply put android does not use standard java classes it needs dex files.
Thus android process for build goes like:
javac -> java2dex -> apk -> sign
That's a lot of work, in fact with jack it should be better however its not that much :)