The #undef directive removes the definition of identifier for a source file containing one or more class definitions. All subsequent tests of the identifier within that source file will evaluate to false. Like the #define directive, any #undef directives must appear at the beginning of a source file, before anything except comments or other conditional compilation directives.
Syntax
#undef <identifier>
Note that the Visual J++ Build Manager does not allow per-file build settings. This means that in order to turn on and off conditional identifiers within a single source file, the #define and #undef directives must be used.