What is annotation processing in Java?

annotations, java, javac

Solution

"Annotation Processing" is a hook into the compile process of the java compiler, to analyse the source code for user defined annotations and handle then (by producing compiler errors, compiler warning, emitting source code, byte code ...).

API reference: javax.annotation.processing (Java Platform SE 6).

Problem

Quoting, Sun's Official Java Tutorial Class names, 'HelloWorldApp', are only accepted if annotation processing is explicitly requested What does it mean? And how to apply it?

Original source