What is annotation processing in Java?

Question

Quoting, Sun\'s Official Java Tutorial

Class names, \'HelloWorldApp\', are only accepted if annotation processing is explicitly requested

Answer 1

"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: http://java.sun.com/javase/6/docs/api/javax/annotation/processing/package-summary.html