http://wlplugin.halirutan.de/index.php/downloads
Mathematica plugin for IntelliJ IDEA
For intelligent code assistance and productive development.
Download and Installation
The installation of the plugin can be completely done from within IDEA. Therefore, the only thing you need to do is to download and install the free Community Edition of IDEA. After you have done that, you open the Settings by pressing Ctrl+Alt+S (Cmd+, on OS X) and navigate then to plugins in the right column. On the right side you find now the button Browse repositories... and there you use the search box to find the Mathematica Support. With a right-click on the plugin you can install it. After the suggested restart of IDEA everything is set up. When you create a new project you have now the opportunity to create a new Mathematica module, but this isn't required. Editing Mathematica files will now work even in Java projects.
If you already have one of the IntelliJ products like RubyMine, WebStorm, PhpStorm, PyCharm, AppCode, or Android Studio you can simply install the Mathematica Plugin as described above.