Java regex returns full string instead of capture

Question

Java Code:

String imagesArrayResponse = xmlNode.getChildText("files");
Matcher m = Pattern.compile("path\":\"([^\"]*)").matcher(imagesArrayResponse);

while (m.find()) {
    String path = m.group(0);
}

String:

[{"path":"upload\/files\/56727570aaa08922_0.png","dir":"files","name":"56727570aaa08922_0","original_name":"56727570aaa08922_0.png"}{"path":"upload\/files\/56727570aaa08922_0.png","dir":"files","name":"56727570aaa08922_0","original_name":"56727570aaa08922_0.png"}{"path":"upload\/files\/56727570aaa08922_0.png","dir":"files","name":"56727570aaa08922_0","original_name":"56727570aaa08922_0.png"}{"path":"upload\/files\/56727570aaa08922_0.png","dir":"files","name":"56727570aaa08922_0","original_name":"56727570aaa08922_0.png"}]

m.group returns

path":"upload\/files\/56727570aaa08922_0.png"

instead of captured value of path. Where I am wrong?

path = m.group(1);

Avinash Raj
– Avinash Raj

2015-12-17 10:12:03 +00:00
Commented Dec 17, 2015 at 10:12 — Avinash Raj
– Avinash Raj, Commented Dec 17, 2015 at 10:12

TEXHIK · Accepted Answer · 2015-12-17 11:27:06Z

5

See the documentation of group( int index ) method

When called with 0, it returns the entire string. Group 1 is the first.

To avoid such a trap, you should use named group with syntax : "path\":\"(?<mynamegroup>[^\"]*)"

javadoc:

Capturing groups are indexed from left to right, starting at one. Group zero denotes the entire pattern, so the expression m.group(0) is equivalent to m.group().

edited Dec 17, 2015 at 11:27

TEXHIK

1,3981 gold badge11 silver badges35 bronze badges

answered Dec 17, 2015 at 10:13

Prim

2,9782 gold badges18 silver badges30 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Thanga · Accepted Answer · 2015-12-17 10:12:54Z

1

m.group(1) will give you the Match. If there are more than one matchset (), it will be m.group(2), m.group(3),...

answered Dec 17, 2015 at 10:12

Thanga

8,2003 gold badges23 silver badges39 bronze badges

Comments

cadrian · Accepted Answer · 2015-12-17 10:12:55Z

0

By convention, AFAIK in regex engines the 0th group is always the whole matched string. Nested groups start at 1.

answered Dec 17, 2015 at 10:12

cadrian

7,3982 gold badges36 silver badges42 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 11:44:36Z

0

Check out the grouping options in Matcher.

 Matcher m = 
   Pattern.compile(
    //<-     (0)     ->  that's group(0)
    //          <-(1)->  that's group(1)
     "path\":\"([^\"]*)").matcher(imagesArrayResponse);

Change your code to

while (m.find()) {
  String path = m.group(1);
}

And you should be okay. This is also worth checking out: What is a non-capturing group? What does a question mark followed by a colon (?:) mean?

edited May 23, 2017 at 11:44

CommunityBot

11 silver badge

answered Dec 17, 2015 at 10:37

Jan

13.9k3 gold badges35 silver badges58 bronze badges

Collectives™ on Stack Overflow

Java regex returns full string instead of capture

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related