For everything else, you can use JNI bindings. The coding style is similar to using FFI bindings to talk to C libraries. On desktop systems, there are often conflicts between the GC mechanisms used by CL and Java, so this would be something to watch out for on Android as well.
In particular, you shouldn't be surprised if JNI's DetachCurrentThread bites you from behind. (When I was working with Rich Hickey's JFLI a few years back, this call typically SEGVed in foriegn code or caused random corruption in Java internals. I ended up recycling threads myself rather than letting them go altogether.)
- nick