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no return value

4 replies on 1 page. Most recent reply: May 10, 2002 1:27 PM by Matt Gerrans

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Michael

Posts: 2
Nickname: mystic
Registered: May, 2002

no return value

Posted: May 10, 2002 9:06 AM

public SerialPort schnittstelleOeffnen(CommPortIdentifier comid)
{
SerialPort sp;

try
{
sp = (SerialPort)comid.open("test", 100);
return (sp);
}
catch (PortInUseException e)
{
System.exit(1);
}
}

Compiler says that the method does not return a value! I think it's because there is no return in case of an Exception. Can somebody help me with that?

thx
mystic

Singh M.

Posts: 154
Nickname: ms
Registered: Mar, 2002

Re: no return value

Posted: May 10, 2002 9:26 AM

you guessed it right. just put a return null at the end.

Michael

Posts: 2
Nickname: mystic
Registered: May, 2002

Re: no return value

Posted: May 10, 2002 9:51 AM

it works, thx alot :)
i only wonder because i was quite sure i tried that out too, however thx again

Matt Gerrans

Posts: 1153
Nickname: matt
Registered: Feb, 2002

Re: no return value

Posted: May 10, 2002 1:20 PM

You might want to consider using the finally clause in this case; it is executed whether an exception is thrown or not. Here is how I would do it:

   public SerialPort schnittstelleOeffnen(CommPortIdentifier comid)
   {
      SerialPort sp = null;
 
      try
      {
         sp = (SerialPort)comid.open("test", 100);
      }
      catch( PortInUseException piue )
      {
         // System.exit(1);
         // Try to handle the problem here, or show some useful
         // information to the user about how to solve the problem.
         // For example:
         System.out.println( "Error: Cannot open the serial port because " + 
                             "it is currently in use by another process." );
      }
      finally
      {
         return sp;
      }
   }

Alles Gute!

Matt Gerrans

Posts: 1153
Nickname: matt
Registered: Feb, 2002

Re: no return value

Posted: May 10, 2002 1:27 PM

Additionally, rather than silently exit() from a catch clause, you may as well not catch the exception and let it bubble up to the caller. (Yes, I realize this is probably testing-in-progress code and that you are the only one who will see it, but you'll be treating yourself better if you can see more of the exception information).

   public SerialPort schnittstelleOeffnen(CommPortIdentifier comid) throws PortInUseException
   {
       return (SerialPort)comid.open("test", 100);
   }

Of course, that would kind of obviate the need for your method, since you could just call the comid.open() method in the code that is currently calling schnittstelleOeffnen().

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