Java language annotations, introduced in Java 1.5.
JSR 175: A Metadata Facility for the JavaTM Programming Language http://www.jcp.org/en/jsr/detail?id=175
Java 1.5 lets you add metadata to your source files, to drive the compilation process, and/or be used at runtime to modify the operation of your programs.
URLs:
Tools that enable you to do Java annotations (JSR 175) in a Java 1.4 environment: