Synthetic Class in Java

Question

What is a synthetic class in Java? Why should it be used? How can I use it?

Answer 1

According to this discussion, though the language specification describes an "isSynthetic" proprty for classes, this is pretty much ignored by implementations and not used for either dynamic proxies or anonymous classes. Synthetic fields and constructors are used to implement nested classes (there is not concept of nested classes in byte code, only in source code).

I think that the concept of synthetic classes has simply proven to be not useful, i.e. nobody cares whether a class is synthetic. With fields and methods, it's probably used in exactly one place: to determine what to show in an IDE class structure view - you want normal methods and fields to show up there, but not the synthetic ones used to simulate nested classes. OTOH, you DO want anonymous classes to show up there.