where to save java files for use in terminal ide in android

I am creating 3 different java files that is linked to each other and i am using java editor in my android tablet 4.4.2 kitkat.

I also have Terminal IDE as my compiler. I have seen that there are samples saved in 'system/src' like helloworld.java I would like to know where to save future java files outside terminal ide. I am not acquainted with its commands and i am having difficulties with it like :wp and everything else.

I cant seem to find the 'system/src' folder in my storage.