ANTLR generates Java code that references a runtime library
to be completed...
The doxygen generated documentation for the Java runtime API is at http://www.antlr.org/api/Java/index.html.
See http://antlr.org/hudson/job/ANTLR_Runtime/lastSuccessfulBuild/org.antlr$antlr-runtime/ for a jar file with the JavaDoc for the latest build of the Java runtime API. Apparently, the plans are for future releases (starting with 3.1.2) to have their JavaDoc available online (see http://www.antlr.org/pipermail/antlr-interest/2009-February/032720.html).