You are not directly using java.io, so why would you need to include it? If you run your code using -verbose:class you will see all of the classes as they get loaded. According to your question, if you needed to include everything used by anything else you reference, everything in the code base would have to include everything else.
Instead we allow ourselves to refer to the things we need directly, and allow them to include the parts they require.
I'd like to finish with three questions: 1) is this a serious question? 2) how is it advanced? 3) why do you include ' ' in you posts?