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Java Forum / General / November 2006

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Quick Question

Thread view: 
C Student - 08 Nov 2006 04:35 GMT
Hi All,

I am going through the java tutorials on the sun web site. I noticed
that their examples for the main method has a void return type. In
other languages you tend to use an int return type and send either a 1
or a 0 to the operating sytem when exiting.

I was wondering if you are meant to do this in java and if not why
doesn't java return a value to operating system as is typical in other
 languages.

Below is a code example.

public class hello {
    public static void main(String[] args) {
        System.out.println("hello");
    }
}

Cheers
Andrew Thompson - 08 Nov 2006 04:46 GMT
Sub:  Quick Question

For 'quick answers', try more meaningful titles..

> I am going through the java tutorials on the sun web site. I noticed
> that their examples for the main method has a void return type. In
> other languages you tend to use an int return type and send either a 1
> or a 0 to the operating sytem when exiting.

Note that a Java application does not necessarily exit
at the end of the main.  A good example is if a Frame is
constructed and set visible - GUIs have their own thread(s).

> I was wondering if you are meant to do this in java and if not why
> doesn't java return a value to operating system as is typical in other
>   languages.

It can.
 System.exit(0) // for a 'normal' exit code,

 // (where n is a non-zero integer)
 System.exit(n) // for anything else

Andrew T.
Simon Brooke - 08 Nov 2006 08:58 GMT
> Hi All,
>
> I am going through the java tutorials on the sun web site. I noticed
> that their examples for the main method has a void return type. In
> other languages you tend to use an int return type and send either a 1
> or a 0 to the operating sytem when exiting.

You mean, you do in C.

> I was wondering if you are meant to do this in java and if not why
> doesn't java return a value to operating system as is typical in other
[quoted text clipped - 7 lines]
>      }
> }

System.exit( 1).

Signature

simon@jasmine.org.uk (Simon Brooke) http://www.jasmine.org.uk/~simon/
       "The result is a language that... not even its mother could
       love.  Like the camel, Common Lisp is a horse designed by
       committee. Camels do have their uses."
                                   ;; Scott Fahlman,  7 March 1995

Eric Sosman - 08 Nov 2006 15:58 GMT
C Student wrote On 11/07/06 23:42,:
> Hi All,
>
[quoted text clipped - 6 lines]
> doesn't java return a value to operating system as is typical in other
>   languages.

   Because in Java the program is not necessarily finished
when main() is finished.  A Java program can consist of many
different execution threads, and the fact that just one of
them has terminated doesn't mean they all have.

   A fairly common pattern is for main() to initialize the
application and then return, having completed its job.  The
bulk of the application keeps on running, using other threads.

Signature

Eric.Sosman@sun.com

www.pulpjava.com - 08 Nov 2006 23:15 GMT
A void method is void of a return. That's why it's void.

There are some great tutorials on Java and J2EE development here:
www.mcnz.com

Cheers!

-Cameron McKenzie

www.pulpjava.com
www.scja.com
www.examscam.com
www.technicalfacilitation.com

> C Student wrote On 11/07/06 23:42,:
> > Hi All,
[quoted text clipped - 16 lines]
> application and then return, having completed its job.  The
> bulk of the application keeps on running, using other threads.


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