In all the hiring I've been involved in1, it'd be much more helpful to show something that you've built, in whatever language, than to show a certification. A github account featuring actual working code is better in two ways. First, it's much closer to what someone actually wants to hire you to do. No one pays interns to pass tests for a summer, but (at least where I work) we do pay them to ship code. Second, if you're being interviewed by programmers (and if you aren't, that's a strong signal that you probably don't want that internship), real live code is a much better jumping off point for an interview. There aren't really any followup questions to "Oh, so you have an Oracle Java cert? Yep." (Except maybe "How was it? Long and boring.", which is not an awesome conversation.) But a good interviewer will have any number of things to ask about code you've written. Being able to hold a deep conversation about code that you've written yourself is tragically rare among interviewees, even though it's a really significant fraction of the job they're interviewing for.
1: Admittedly, this sample is neither particularly broad nor deep, but there it is
As long as I am alive and well I will continue to feel strongly about prose style, to love the surface of the earth, and to take pleasure in scraps of useless information.
~ George Orwell