ZK - Open Source Ajax Java Framework

Hi
I'm new aith ZK. I installed the ZK plugin and built a sample project. I get the error java.lang.String.isEmpty() method doesn't exists. It seems that if I change the compiler version to 1.6 it works. For me it doesn't work. Besides, the project validator signas an error: the project is faceted to Java 1.5 and cannot be greater that that. So compiler change to 1.6 does not like Eclipse.

Any ideas?

You may remove breeze.jar first.
breeze.jar seems like use some api only available in java 6.