Inner class identifiers
Since every class produces a .class file that holds all the information about how to create objects of this type (this information produces a “meta-class” called the Class object), you might guess that inner classes must also produce .class files to contain the information for their Class objects. The names of these files/classes have a strict formula: the name of the enclosing class, followed by a ‘$’, followed by the name of the inner class. For example, the .class files created by LocalInnerClass.java include:
If inner classes are anonymous, the compiler simply starts generating numbers as inner class identifiers. If inner classes are nested within inner classes, their names are simply appended after a ‘$’ and the outer class identifier(s).
Although this scheme of generating internal names is simple and straightforward, it’s also robust and handles most situations. Since it is the standard naming scheme for Java, the generated files are automatically platform-independent. (Note that the Java compiler is changing your inner classes in all sorts of other ways in order to make them work.)