Project Coin: IDE support
By Darcy-Oracle on Apr 21, 2011
All three of the NetBeans, IntelliJ, and Eclipse IDEs have some level of support in progress for Project Coin's language features.
The recently released NetBeans 7.0 has support for all the Coin features. As explained in its release notes, beyond just recognizing the features in the editor NetBeans 7.0 provides auto-completion to diamond and gives hints to apply the new features to existing code.
Finally, an Eclipse branch is hosting their efforts to support Project Coin.
As JSR 334 is not quite done yet, I'd expect the IDEs to be updated after JSR 334 is completed to account for any specification changes made in the interim.