This week's book giveaway is in the Agile and Other Processes forum. We're giving away four copies of Darcy DeClute's Scrum Master Certification Guide: The Definitive Resource for Passing the CSM and PSM Exams and have Darcy DeClute on-line! See this thread for details.
In Chapter 6, page 282, in the first paragraph of "Applying Class Access Modifiers" it says:
Also remember that a .java file can have at most one top-level class.
I think what the authors meant to say is that at most one "PUBLIC" top-level class is allowed in a .java file. In principle you can have as many top-level classes as you want in a single file, like in the example that follows in which they defined: