Randall, if a (Windows) user double clicks on a .jar file, 'javaw.exe" is invoked, so that is how my users run my .jar file. I sometimes use the Command Prompt, where I can invoke either java.exe or javaw.exe.
Thanks for your response Rob. As the comment in my code indicates, the setting for defaultCloseOperation appears to have no bearing on the problem. I have tried all possible values, including the default (which I believe is HIDE_ON_CLOSE, but I could be wrong). The behavior is the same in all cases: i.e. program isn't terminated on shutdown/logoff.