Difference between multithread and multiprocess

[Jane Somerfield]

How the multiprocess is done in Java?

[Ernest Friedman-Hill]

"Multiprocessing" isn't really a term with a precise meaning in this context; but on most operating systems the definition of a process is running code with its own address space, and a thread shares its address space with other threads; generally a process can contain one or more threads.
Therefore "multiprocessing in Java" would imply starting multiple separate processes -- i.e., multiple separate JVMs. If one JVM wanted to start another, it would use the Runtime.exec() family of methods.