Because I'm in C# all the time, my Java is passable with effort, but not pristine - like a Norwegian's use of Swedish or a Portuguese person required to use Spanish.

But there's good reasons to hang onto that Java; it seems like Google interviews may require rapid prototyping in the language.

Most algorithms are language agnostic (save the ones that leverage language features (think functional)) but it's also interesting to see that quick deployment of those with optimizations seems to be a part of the process.