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The answer is E and I understand up to the point of there being a '6' at the end. of the output. I was thinking in terms of indexes so I don't understand why the output doesn't end at 5.

hi,
I have a question about this code and found this post through search so i thought of asking here.
the m.find() method returns true if it gets a match, so how is it possible that code gets executed inside the while loop before 34?

That's because the regular expression did find a match. Since the regular expression is looking for zero or more occurrences of a digit, it finds a blank match at each index in the string...

Ankit Garg wrote:That's because the regular expression did find a match. Since the regular expression is looking for zero or more occurrences of a digit, it finds a blank match at each index in the string...

oh yea! i never thought of that! i thought the first match has to be a digit followed by zero or more digits. Thanks.
It has been a very busy week here at work, i couldn't concentrate at all while studying, i felt like i'm hitting

I had posted this in reponse to another post regarding the same thing, so I thought id just copy it here as well.

The regex pattern \d* matches ZERO or MORE digits. The key thing to note is the ZERO possiblity.

m.find() Matcher class method definition: Attempts to find the next subsequence of the input sequence that matches the pattern.
m.start() Matcher class method definition: Returns the start index of the previous match.
m.group() Matcher class method definition: Returns the input subsequence matched by the previous match.

Upon the first iteration (b = m.find()) is set true because the * matches on ZERO digits found.

Imagine the string as looking like this |0|a|1|b|2|3|3|4|4|e|5|f|6|
Where the bold characters are part of the string, and the numbers indicate an index

m.start() = 0 (The "space" behind the "a", I guess you could say. The darn * gets that I believe)
m.group() = ""

m.start() = 1
m.group() = ""

m.start() = 2
m.group() = "34" MATCH OCCURED!

The skip of the index occurs because the match covered the |3| index. Say it was "345" in the string then group would be "345" and m.start() would be 5 on the next iteration.

m.start() = 4
m.group() = ""

m.start() = 5
m.group() = ""

m.start() = 6
m.group() = ""

I believe this is how it works anyway...I ran a quick test with the same pattern trying to match "" and it came back with m.start() with index 0!

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Scotty Mitchell wrote:I had posted this in reponse to another post regarding the same thing, so I thought id just copy it here as well.

The regex pattern \d* matches ZERO or MORE digits. The key thing to note is the ZERO possiblity.

m.find() Matcher class method definition: Attempts to find the next subsequence of the input sequence that matches the pattern.
m.start() Matcher class method definition: Returns the start index of the previous match.
m.group() Matcher class method definition: Returns the input subsequence matched by the previous match.

Upon the first iteration (b = m.find()) is set true because the * matches on ZERO digits found.

Imagine the string as looking like this |0|a|1|b|2|3|3|4|4|e|5|f|6|
Where the bold characters are part of the string, and the numbers indicate an index

m.start() = 0 (The "space" behind the "a", I guess you could say. The darn * gets that I believe)
m.group() = ""

m.start() = 1
m.group() = ""

m.start() = 2
m.group() = "34" MATCH OCCURED!

The skip of the index occurs because the match covered the |3| index. Say it was "345" in the string then group would be "345" and m.start() would be 5 on the next iteration.

m.start() = 4
m.group() = ""

m.start() = 5
m.group() = ""

m.start() = 6
m.group() = ""

I believe this is how it works anyway...I ran a quick test with the same pattern trying to match "" and it came back with m.start() with index 0!