[jdom-interest] Re: [jdom-commits] CVS update: jdom/src/java/org/jdom/input

Jason Hunter jhunter at acm.org
Sat Mar 2 15:54:18 PST 2002

> --- cvs at jools.org wrote:
> > Changed some string comparators from != to !.equals().  The former works
> > so long as the parser interns strings, and although Xerces and Crimson do,
> > not all parsers do.  So using !.equals() is safer.  Brad Huffman ran some
> > tests to see if this had much of a performance impact, and surprisingly
> > it didn't and in fact sometimes ran *faster*.  Below is his table, for
> > future reference.
> Of-course it doesn't have much of a performance impact. Look at
> the first three lines of String.equals() :
> if (this == anObject) {
>     return true;
> }
> So, asking
>    if (str1.equals(str2))
> is just like asking
>    if (str1==str2 || str1.equals(str2))

Yes, in the rare event of an exact reference match it's fast.  But that
doesn't happen often.  So your != gets to go right to false while the
.equals() has to start looking at characters.  Luckily most strings
appear to differ on their initial chars and char indexing isn't too


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