Re: string comparison with null
focode wrote:
i have a form in which their are textFields when the user set his data
in that form and press next button i get all the data in form of
string , then i have to check if any field was left empty , if it is
so the application sends the user back to the form to fill the
required field , my problem is i have the value of the textField in
form of string , how will i know that this string contains nothing , i
used compareTo fuction i which the first parameter was string from the
textField and the second parameter i ahve taken an another string
which is null eg
String str = null;
int value = textFIeldString.compareTo(str);
but this throws exception
tell some other way to implement this ..
thanks and regards
Arunesh
There are two very different concepts, a null String reference and an
empty String.
A null String reference is just like a null reference of any other type.
There is no String.
The literal "" represents an empty String, one that exists but has
length 0 and contains no characters. An empty TextField's getText()
returns an empty String, not null.
You probably need to check for empty string, in which case you can
either use textFIeldString.equals("") or textFIeldString.length()==0.
If you every do need to check for null, you can use
textFIeldString==null, just as you would for any other type of reference.
Some people routinely combine the two tests. I rarely, if ever, find a
situation in my code in which a String reference could either be null or
point to an empty String, and the two cases have identical implications
and require identical treatment. If I need to test for both, they often
require different treatment.
Patricia