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





                                                                                
                                           
                    "Gibbons, Michael"                                          
                                           
                    <bmis04@MARYWOOD1.MAR        To:     "'Java-L'" 
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                    Sent by:                     Subject:     compare to a 
blank                                           
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                    06/22/00 12:43 PM                                           
                                           
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hello,

after a field is retrieved via record level access i am having a hard time
comparing to a blank. In rpg on the 400 i would say     (field    ifne
" ")
but i guess that doesn't work. With debug i know the field is empty. I have
been trying this

if(field != " ")    {
          out.println(field);}
else {out.println("Empty"); }

Also tried field != null

any suggestions?
Thanks in Advance

Michael P. Gibbons
Manager of Programming & Technical Services
MARYWOOD UNIVERSITY
2300 Adams Ave.
Scranton, PA 18509

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