Two public classes in one source file

Question

Can anyone please explain what is the exact reason why the java source file name should be same as the only allowed public class name in the source file. Answer only if you know the correct answer. No gusses please. I read the other postings on this topic. None of the answers were correct.

Answer 1

One reason is that some RISC processor architectures
(like those Sun uses mostly) have hierarchical memory
architectures. This hierarchy is divided into global
modules and local (global-accessible) submodules. The
advantage of this is that the processor needs lesser
memory access "points" (handles), as the modules
delegate CPU calls to the submodules.
The java compiler can utilize this and increase
performance by loading the entire source files into
the memory and assign them a CPU handle (the module
ID). It'll be later used for linking, e.g. The public
class in a file will be loaded as a module and gets
the handle, all other non-public classes in that file
will be submodules.
If there is no public class, a generic module will be
used, so that's no problem. But if there are multiple
public classes, you'd end up with several modules and
just one handle to assign, thus having ambiguity. The
CPU won't be able to address the correct module.
This all only applies to RISC CPUs, but for obviuos
cross-platform compatibility reasons it was added to
the standard - it doesn't hurt the other
architectures, but helps those with hierarchical
memory management.Thanks, but the rooster explanation makes more sense to me.
Now could someone please express it a la Majinda?