It could be a useful addition to your repertoire of languages (most employers will recognise the benefit of having experience of some different languages even if they're employing for just one). However personally, I would play to your strengths and if anything concentrate on improving your knowledge of Android, this will likely help consolidate your existing Java knowledge. Even now there are still much more jobs looking for core language experience than mobile.

Java skills are very much in demand, and you are in a good position if you have decent experience of the language - if you do go down that route I would make sure you have some knowledge of Java EE, infrastructure frameworks like Spring and Hibernate and front-end web frameworks like GWT, JSF etc.

You don't say where you are from but I'm guessing the UK - There are usually a few Java jobs to be found in London and Cambridge as well as the M4 corridor areas.