In the next release of Bio7 the full Java 7 Syntax will be availabe for the compilation of custom models. In addition the Java error messages will be more informative and errors can be easier detected in the Java source.
At the moment a combination of the Janino compiler and the standard Java compiler makes this possible. I hope to integrate the Eclipse compiler for the compilation support but there seems to be a bug in the classpath options of the compiler when used programmatically (standard compilation works dynamically).
However, this is definitevely a great compilation improvement for the next Bio7 release.