I work with JDK 7 in Intellij 12.0.4. When I try to create a multi-catch block it get a "multi-catches are not supported at this language level" error. I found this question but the answer doesn't work for me. This was the answer:
Click on the File menu, open Project Structure, then under "Settings" there should be "Project". Within that tab, there'll be an SDK Settings option which specifies the language version you want to use. See the JetBrains help page for more details ("Project language level").
In Project Structure -> Project Settings -> Project, set the Project language level to 7.0 - Diamonds, ARM, multi-catch etc. This should fix your problem.