Update: add information about IntelliJ Idea 14
Java is no longer part of Mac OS default installation. When you want to start Idea on new Mac OS Yosemite you’ll get this nice message:
IntelliJ Idea 13
In case of Java 8, just open file “/Applications/IntelliJ IDEA 13.app/Contents/Info.plist” and change JVMVersion from 1.6* to 1.8*:
sudo vim "/Applications/IntelliJ IDEA 13.app/Contents/Info.plist"
IntelliJ Idea 14
Open file “/Applications/IntelliJ IDEA 14.app/Contents/Info.plist” and change JVMVersion from 1.6* to 1.8*:
sudo vim "/Applications/IntelliJ IDEA 14.app/Contents/Info.plist"
Click IntelliJ Idea icon and enjoy your IDE.
You can find more info at JetBrains Support forum.