One way to convert it would be to get a Java to C translator, which will generate C for you, and you can then use a C compiler to generate assembly code. Compilers will in general produce object code, but if you dig through the manual you'll find the option that will produce an assembly language listing.

A quick Google finds which describes the DLX Compiler & Assembler and its -l option to generate assembly. Another ("java to c") finds a number of Java to C translators which could be up to the job.