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return & system.exit()

 
Ranch Hand
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Is using "return" or "System.exit()" same if used in main() method ?

Thanks.
 
author and iconoclast
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Returning from main() will only stop the program if no other non-daemon threads are running. So, for example, if the program has a GUI, then the event thread is running, so returning from main will not stop your program.

System.exit() will, however, stop your program no matter how many threads are running.
 
Ambika Jain
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Thanks for the reply.
If I am validating the arguments passed to the program, should I use system.exit() or return, if the arguments are invalid.

Thanks.
 
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System.exit() is a more abrupt way to stop your program. For example, if you call System.exit() from a try or catch block, any finally clause is ignored. System.exit() may be the most practical was to stop applications like Java Swing that have never-ending non-daemon threads.
 
Greenhorn
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If it was me, I'd display some friendly message to the user saying what argument(s) was bad and why, then return from the main method.
 
Mike Gershman
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When in doubt, use return. It cleans up better before shutting down.
 
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The nice thing about System.exit() is that you can pass an error code that, if the JVM is set up correctly for the O/S, it should pass to whomever called your program. This is why in C main() returns int.
 
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