RSTALanguageSupport
A Java library that adds code completion, parsing and error-underlining for languages such as Java, JavaScript, C, CSS and HTML to the RSyntaxTextArea text-editing component.
RSTALanguageSupport adds per-language support to RSyntaxTextArea, a Swing text-editing component. For each supported language it provides some combination of auto-completion for function and variable names and a parser that underlines syntax errors in the source. It depends on RSyntaxTextArea and AutoComplete, and uses the Rhino engine to implement JavaScript's code completion and syntax checking.
Support varies by language: Java completion draws on a parser that reads JDK class structure and extracts members and local variables for suggestions, and adds a member-outline tree view and a go-to-member popup; C offers completion for the standard library; CSS completes selectors, properties and some values; HTML completes tags and attributes; Groovy support is described as currently broken. The library is released under a modified BSD license.