RE: compare to a blank

 Hello,


You may also want to consider the following since it is just as readable and
_faster_ than the equals() method.  With length(), you won't make a hard to
see mistake like using " " instead of "".  These bugs can be very hard to
see in some editors and on printouts.  Also, it will in help get rid of some
of those oops "I used '==' instead of the equals()" bug.

        if (field.length() == 0)
        {
        }
        else
        {
        }

-or-

        if (field.trim().length() == 0)
        {
        }
        else
        {
        }

/Tim


> -----Original Message-----
> From: Pluta@nexgensoftware.com [SMTP:Pluta@nexgensoftware.com]
> Sent: Thursday, June 22, 2000 12:11 PM
> To:   JAVA400-L@midrange.com
> Subject:      Re: compare to a blank
> 
> 
> This was one of the most common gotchas in Java programming for me.  You
> cannot use the "==" and "!=" operators to compare two String objects (or
> any two objects, for that matter).  That's because those operators compare
> the object IDENTITIES rather than their CONTENTS.  That is, it's checking
> to see whether the field (named "field") and the constant blank are THE
> SAME OBJECT.  Obviously, they are not: one is a field, one is a constant,
> and they are stored in different objects.
> 
> You can compare the contents of two String objects with the "equals"
> method, like so:
> 
> if (field.equals(" "))
> {
>      // Do equal logic
> }
> else
> {
>     // Do unequal logic
> }
> 
> Another warning, though: a one-character blank field is NOT equal to a
> two-character blank field!  Leading and trailing blanks are significant.
> So unless the field you were looking at is a one-character field,
> comparing
> to a single blank will not work.  On the other hand, you can use the
> trim()
> method to remove trailing blanks, and then compare to an empty String:
> 
> if (field.trim().equals(""))
> {
>      // Do equal logic
> }
> else
> {
>     // Do unequal logic
> }
> 
> Note that there are NO spaces between the double quotes.
> 
> Hope this helps.
> 
> 
> Joe Pluta
> www.java400.net
> Moderator
> 
> +---
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