The simplest example I have is here:http://fifesoft.com/rsyntaxtextarea/examples/example5.php
It shows adding code completion for Java keywords.
I'm working on some straightforward guides that explain how to add custom syntax highlighting, code folding, and code completion for languages, but it's not ready yet. I'm too lazy to complete them! They'll hopefully be available soon.
One good example that may be worth exploring is the C code completion in the RSTALanguageSupport project. It's "simple" in that it loads all of its completions from XML, so the amount of actual Java code written for it is very small. It doesn't really do any parsing; rather, based on the RSTA token it's in (comment, string, or "code" - e.g., everything else), it surfaces a different list of possible completions and lets the machinery do all the work. The heart of it all is the CCompletionProvider
class, which mostly loads the completions from XML. The XML is expected to follow this DTD
found in the AutoComplete project, then everything should "just work." You should be able to follow the simple example above, but load your completions from XML instead of hard-coded BasicCompletions.
Again, I hope to have a simple tutorial for this stuff in the near future, but hopefully this is enough to help you get started. Let me know if you have further questions.