Remember though that all MS Windows is just a GUI built on top of the DOS OS (XP billed as not being the case...??).
All that "java" is is just a bunch of files stored in the DOS FAT32 file system ... and all the 'javac' compiler and 'java' interpreter are just .exe programmes ... The JVM is just a means of compiling and interpreting java source code into executable native machine code ...
Without a hard drive though, there is no way that you can have enough space on the floppy to store the programmes and library files needed to execute compilation and interpretation of java source code - but in theory I guess if the machine was networked, and all programmes and files were stored on a networked machine, and the PATHS/CLASSPATHs were set up, then I guess you'd be OK ??!!
Mad, but probably OK anyways.