For any particular version of Ubuntu, the standard repositories are rarely updated with newer versions software. Software is only updated for critical support issues and for security reasons.
Exceptions are made for critical pieces of software such as Firefox that Canonical say they support. In these cases, a decision is made whether the software is about to lose support upstream. If it is, then a newer version in the repository is updated.
As far as I can see "groovy" isnt a Canonical supported piece of software and hence will not be updated to a newer version.
To obtain newer versions of software, you will need to either download the source-code yourself and compile and install it - or find a trusted PPA where the packager has done the compilation for you.
V1.8 of Groovy was released at the end of last month. Even the next version of Ubuntu (11.10) does not have this version in its repositories.