[felipemnoa]

If you do that you will no longer be able to tell the overall structure of your project at a single glance without using an IDE like Eclipse. Adding and removing packages becomes harder without the IDE. What are the upsides? You've increased the complexity for no good reason.

[morsch]

Easier rapid prototyping and exploratory programming. Edit all the classes of your small/exploratory project in a single file. If the project expands, it should be an automated refactoring to move classes to their own files.

I do this all the time using static inner classes.