Android or Java class naming with $ symbol

I'm reviewing a certain project and I see that there are many classes with the same name, but with a dollar ($) symbol at the end + increasing number. For example

Class.ja开发者_StackOverflow社区va
Class$1.java
Class$2.java
Class$n.java
OtherClass.java
OtherClass$1.java
OtherClass$n.java

What does it mean?

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AFAIK if it's has number it's an anonymous inner class, if it has a name after $ sign it means just inner class.
Edit: More about how compiler handles you can see here

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The dollar sign is used by the compiler for inner classes. I thought it would be strange to manually make classes/files with those names though: As far as I know it's a compiler thing.