How do I make a java program that reads from both a file and a URL?

I know the syntax to write a program that reads from a file and the syntax to read from a URL, but I need to be able to have a program that does both. I am thinking it will need to be an If statement, but I'm not sure what to do. They said I can count on the URL starting with http..... Anyone help me set up the if statement? Thanks!