Now your just exposing your incompetency. It will be easy for an experienced programmer to adapt with new code, since a lot of building blocks for a program is almost the same. PHP and Java, both have variables, if-else, loop, you name it.
Understanding code is one thing, but apprehending the context is another.
It wouldn't be difficult if enough documentation provided. As I have asked the dev to create a wiki for the community to join force in development previously, only to find it fall to a non responsiveness. Look at bitcoin developer documentation for instance [1], from there, a lot of third party app like bitcoin Android Wallet may existed.
sources
1-
https://bitcoin.org/en/developer-documentation