I used DefaultWysiwygConverter (from http://mvnrepository.com/artifact/com.atlassian.renderer/atlassian-renderer/8.0.5) to convert HTML to Wiki markup, but didn't manage to do the opposite. I tried following:
DefaultWysiwygConverter converter = new DefaultWysiwygConverter();
RenderContext context = new RenderContext();
String wikiMarkup = ...
String html = converter.convertWikiMarkupToXHtml(context, wikiMarkup);
But this failed, since apparently something called "WikiStyleRenderer" was not defined in DefaultWysiwygConverter.
Any tips on how to get Wiki markup to HTML work?