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Thread: returning null instead of int

  1. #1
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    Default returning null instead of int

    Hi,
    I have the following code. The point is to test returns.

    public class objects
    {
        public static void main(String[]args)
        {
            int x = 0;
        }
     
        public int testZero(int x)
        {
            if (x == 0)
                {
                    System.out.println(x);
                    return ;
                }
            else
                {
                    return x;
                }
        }
    }

    As is, I get a "missing return value" error from the compiler for the line "return ;", line 13. If I remove that statement, I get "missing return statement".
    How should/could I handle this? If my method has a return type, MUST I return a value of that type? Is there a way not to do that?

    Thank you,
    Mike


  2. #2
    Super Moderator helloworld922's Avatar
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    Default Re: returning null instead of int

    an int can never have a null value because it's a Java primitive. However, there are wrapper classes for primitives which can be null.

    ex.:

    // didn't test run this, hopefully it works
    public Integer testZero(int x)
    {
        if(x == 0)
        {
            return null;
        }
        else
        {
            return x;
        }
    }

    Every execution path must end in either a return value or throwing something (usually an exception). There are a few odd cases where a method doesn't terminate normally (for example, System.exit()), but these are rare.

    Why not use booleans? These are meant to hold true/false values, ideal for answering yes/no type questions.

    public boolean isZero(int x)
    {
        if(x == 0)
        {
            return true;
        }
        else
        {
            return false;
        }
    }

  3. The Following User Says Thank You to helloworld922 For This Useful Post:

    youngstorm (November 19th, 2012)

  4. #3
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    Default Re: returning null instead of int

    Hello Mike!

    Quote Originally Posted by youngstorm View Post
    How should/could I handle this? If my method has a return type, MUST I return a value of that type? Is there a way not to do that?
    Yes, you are correct. You must return a value of that type. There is no way you can avoid that - as far as I know.
    A common way to handle this situation is to have some "default" return values. For example, return 0 for default or -1 for an error. Then in your program you can check if these values are returned and handle them accordingly.

    Hope this helps.

  5. The Following User Says Thank You to andreas90 For This Useful Post:

    youngstorm (November 19th, 2012)

  6. #4
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    Default Re: returning null instead of int

    Thanks to both of you for your help. This is the info I was looking for. Also, glad to know about the wrapper classes, that will do what I was hoping to do. Again, no special reason; I'm just playing and learning.

    Thanks again guys.

    --- Update ---

    How do I mark this thread as solved?

  7. #5
    Super Moderator helloworld922's Avatar
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    Default Re: returning null instead of int

    At the top, under Thread Tools > Mark this thread as solved

  8. #6
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    Default Re: returning null instead of int

    Thanks again.

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