As of version 3.10 Helpinator supports the following Java-oriented help systems:
The most powerful and well-thought help system for Java created by Oracle Corporation. Has two “branches”: OracleHelp for Java and OracleHelp for Web. New versions come out regularly.
Blog post about OracleHelp:
Original Java help system. Outdated and is not under active development.
Blog post about JavaHelp:
A lightweight help system with a limited set of features.