System.exitshould be used with care. The normal method of terminating a program is to terminate all user threads.
Cases in which
System.exit is appropriate:
System.exit, or, for example, by setting:
From Oracles's Portability Cookbook:
System.exit method forces termination of all threads in
the Java virtual machine. This is drastic....
be reserved for a catastrophic error exit, or for cases when a program
is intended for use as a utility in a command script that may depend on
the program's exit code."