How should nested Java classes be named?

[HosseinYousefi]

Currently a class Bar nested in Foo is named Foo_Bar. Using underscores could be problematic as the class Foo_Bar itself could technically exist even though using underscores in Java class names are rare.

The way Java bytecode names this is using a dollar sign like Foo$Bar and people already familiar with this are not going to be surprised by it.

I would like to change the syntax before 1.0 to use $ instead.