[Help] Finding Java Code parts

Ok here is my Question, i allready tryed to find it via google etc. i would like to ask how can i extract complete codes for example.

i got a source and it has a event engine how can i find all the codes in the other files that are needed/linked whit the engine. since i can create a diff because i didnt add anything. do i have to use "normal" search function in each file that is listed as import for the code or is there a function in the eclipse.

hope you got what i mean