Henry,
CodeMix is for modern web development. You can use CodeMix as part of HTML, JS, CSS files of any project type — so for instance if you have web files in the middle of the Java projects you are working with, they will automatically benefit from CodeMix. With the CodeMix’s Java editor, you will see validation / IntelliSense working.
For Java and JSP, we recommend sticking with the editor and support (validation, build, debug, etc.) that’s part of Eclipse – Eclipse’s Java tooling (via JDT) is simply excellent.
Hope this helps. Please let us know if you have any further questions.
–Swapna
Genuitec Support