I know that I have grabbed the apk's from Google Play before and then decompiled them to compare with the original sources. What I did was compile my own versio

I know that I have grabbed the apk's from Google Play before and then decompiled them to compare with the original sources. What I did was compile my own version, then decompile it again and compare those source with the decompiled original sources. There were some differences where the compiler/decompiler made a different decision, and that had to be checked out manually but in the end it was a pretty nice experience.