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Matcher.find() APIs unexpected Behaviour

 
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Hi,

I am not able to understand un-expected behaviour of find() API of Matcher class.
As per the java documents and my understanding, find() method return TRUE if system is able to find more occurence of sequence that matches given the pattern.

public class RejEx {

public static void main(String[] args) {
String source = "pp";
Pattern p = Pattern.compile("p*");
Matcher m = p.matcher(source);
while(m.find())
{
System.out.println("Pattern Found :"+m.group());
}
}
}

As per the code snippet,anybody will expect that while loop should get executed only once but it gets executed 2 times. So when I run this program I get output as below :
Pattern Found : pp
Pattern Found :

I does work fine if I use "p+" pattern but if use "p*" or "p?" as pattern than I am not getting output as per my expectation.

So now I have following questions :
1. Is my understanding not correct ?
2. Is there any BUG in find() API ?

cheers,
Sunil

[ May 14, 2008: Message edited by: Sunil Dixit ]

[ May 14, 2008: Message edited by: Sunil Dixit ]
[ May 14, 2008: Message edited by: Sunil Dixit ]
 
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The javadocs of Matcher.group actually mention why this is happening. (Well, they do for "a*", but the principle still holds :-)

After reading that you may wonder why the same isn't happening at the beginning of the string - for an answer to that, read up on the concept of "greedy matching" (which is what the "*" special character does).
 
Sunil Dixit
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Thanks a lot buddy !
 
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