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Re: can't return value

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On 9/12/2012 3:36 AM, bilsch wrote:
> I want to get variable lastName for use in the main method (the whole
> program isn't shown). I want to return it from inside the IF block within
> the FOR loop.  The compiler complains there is no RETURN statement when I
> have it there.  It stops complaining if I put RETURN two brackets lower
> (notice it is commented out there).  The variable lastName isn't visible to
> the RETURN statement that's located two brackets lower. The variable
> lastName is only visible inside the FOR / IF block.
>
> I thought passing variables was a way to get around the visibility problem -
> but I'm stuck anyway.  Does anyone have a suggestion?  TIA  Bill S.

     Although your method contains a `return' statement, the
compiler has noticed that the `return' might not always be
executed.  Since you only execute the `return' after detecting
a space character in `wholeName', what happens if `wholeName'
contains no spaces?  Answer: The `for' loop completes[*]
without ever reaching the `return', and then where are you?

     You need to decide what to do if there is no space in
`wholeName': throw an exception, return `null', whatever you
like -- but the compiler will not allow you to just ignore
the possibility.

     [*] Actually, the loop will not complete.  If there is
no space in `wholeName', you will eventually get an exception
when you call charAt() with an argument that's beyond the
end of the string.  In fact, then, the analysis I've given
above is not quite correct: execution will never get to where
the commented-out `return' is.  But (1) the compiler cannot
"see" the fact that charAt() will throw, and (2) if you fix
the error in the `for' loop the analysis becomes correct again.

     Aside: There are at least two easier ways to find the
pieces of `wholeName'.  The String class has indexOf() and
lastIndexOf() methods that can find the space character for
you, and also has a split() method that can both find the
spaces and chop the string into space-separated pieces.

     Aside II: Re-read the documentation of the substring()
method; there's a surprise awaiting you.

> public class Name01{
>
>      public static String lastName(String wholeName){
>       for (int i = 0; i <= wholeName.length(); i++){
>           if (wholeName.charAt(i)== ' '){
>              String lastName = wholeName.substring(i,wholeName.length()-1);
>              //System.out.println(lastName);
>              return lastName;
>           }
>       }
>       //return lastName;
>      }
>
>
>      public static void main(String[] args){
> String  wholeName = "Bill Jones", last;
>      last = lastName(wholeName);
>      System.out.println("lastname is: " + last);
> }
> }
>
>


-- 
Eric Sosman
esosman@ieee-dot-org.invalid
"The speed at which the system fails is usually not important."

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Thread

can't return value "bilsch" <king621@comcast.net> - 2012-09-12 00:36 -0700
  Re: can't return value Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-09-12 07:11 -0400
    Re: can't return value bilsch <bilsch01@gmail.com> - 2012-09-12 22:15 -0700
      Re: can't return value Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-09-13 08:53 -0400
  Re: can't return value Jukka Lahtinen <jtfjdehf@hotmail.com.invalid> - 2012-09-12 15:32 +0300
    Re: can't return value bilsch <bilsch01@gmail.com> - 2012-09-12 22:37 -0700
      Re: can't return value Lew <lewbloch@gmail.com> - 2012-09-12 23:17 -0700
        Re: can't return value markspace <-@.> - 2012-09-13 01:11 -0700
          Re: can't return value Lew <lewbloch@gmail.com> - 2012-09-13 10:53 -0700
      Re: can't return value Stuart <DerTopper@web.de> - 2012-09-13 09:45 +0200
        Re: can't return value "bilsch" <king621@comcast.net> - 2012-09-13 03:55 -0700
        Re: can't return value Jukka Lahtinen <jtfjdehf@hotmail.com.invalid> - 2012-09-13 15:06 +0300
          Re: can't return value Stuart <DerTopper@web.de> - 2012-09-13 20:53 +0200
  Re: can't return value Roedy Green <see_website@mindprod.com.invalid> - 2012-09-12 20:54 -0700

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