Java regular expression to match patterns in url

Question

I have a bunch of urls that share the following pattern:

http://www.ebay.com/itm/Crosman-Pumpmaster-760-Pump-177-Pellet-4-5-mm-BB-Air-Rifle-Black-760B-/251635693266?pt=LH_DefaultDomain_0&hash=item3a96a7f6d2

I want to extract item3a96a7f6d2. The http://www.ebay.com/itm/ and &hash= are fixed patterns while the string in between can change. I wrote:

                String prodPatternString = "(http://www.ebay.com/itm/)(.*?)(hash=)(.*?)";
                Pattern prodPattern = Pattern.compile(prodPatternString);
                Matcher prodMatcher = prodPattern.matcher(prodUrl);
                while(prodMatcher.find()){
                    String pid = matcher.group(4);
                }

But it gives me an error saying "No match found". Any help will be greatly appreciated. Thanks.

Avinash Raj · Accepted Answer · 2015-02-17 19:10:47Z

1

You need to change matcher.group(4); line to prodMatcher.group(4); and then remove the ? present inside the last capturing group because .*? will do a non-greedy match of zero or more characters, so it would match also an empty string even though characters present since it's in non-greedy form.

String prodUrl = "http://www.ebay.com/itm/Crosman-Pumpmaster-760-Pump-177-Pellet-4-5-mm-BB-Air-Rifle-Black-760B-/251635693266?pt=LH_DefaultDomain_0&hash=item3a96a7f6d2";
String prodPatternString = "(http://www.ebay.com/itm/)(.*?)(hash=)(.*)";
Pattern prodPattern = Pattern.compile(prodPatternString);
Matcher prodMatcher = prodPattern.matcher(prodUrl);
while(prodMatcher.find()){
        String pid = prodMatcher.group(4);
        System.out.println(pid);
}

Output:

item3a96a7f6d2

edited Feb 17, 2015 at 19:10

answered Feb 17, 2015 at 19:05

Avinash Raj

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3 Comments

J Freebird Over a year ago

Thanks a lot! But I still don't understand why the ? needs to be removed in the last capturing group while it is needed in the second capturing group? I think these two patterns are the same. Thanks

Avinash Raj Over a year ago

no both are different. It's based on the following pattern. .*? in this regex http://www.ebay.com/itm/.*?hash= matches all the characters which are next to http://www.ebay.com/itm/, upto hash= . But .*? in hash=.*? matches an empty character because there isn't a pattern following the .*? and .*? will do a shortest possible match. So here the shortest possible match is an empty string since * repeats the previous char zero or more times.

Avinash Raj Over a year ago

you could check what i said with (hash=)(.*?)$

IByrd · Accepted Answer · 2015-02-17 19:07:22Z

0

You should check out the lastindexof method. Then you can substring the url starting at the last index of '&hash=' and ending at the full length of the string. This will get the item=x

answered Feb 17, 2015 at 19:07

IByrd

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Comments

anubhava · Accepted Answer · 2015-02-17 19:08:48Z

0

You can use this regex:

(http://www.ebay.com/itm/)(.*?)(hash=)([^&]*)

RegEx Demo

.*? is matching too little in the 4th capturing group in your regex.

answered Feb 17, 2015 at 19:08

anubhava

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