Replace Character in Matching Regex

Question

I have a substring in a string with the following format:

ID Number: 4D:9B:C4

I am using the following regex to match it:

ID Number: [A-Z0-9]{2}(:[A-Z0-9]{2}){2}

What I want to do is capture instances of substrings matching this regex (or just the first instance), then capture the ID number itself inside, and finally replace colons in the ID Number with spaces, so the output will be:

4D 9B C4

I've been playing around with using capture groups in replace all, surrounding my desired capture in parentheses, like this ....

String idNum = idNum.replaceAll("ID Number: ([A-Z0-9]{2}(:[A-Z0-9]{2}){2})", "$1");

But I'm not sure where to go from here or even if I'm taking the right approach. Any suggestions would be greatly appreciated.

EDIT: Perhaps I didn't phrase this the best way in the description, so I'll illustrate by example. The initial string I'm capturing is a substring within a larger string like ...

We got some text up here
  ID Number: 4D:9B:C4
  And also some text down here

And I want the output previously stated.

try idNum.replaceAll("ID Number: |:"," ").trim() that will return 4D 9B C4 — Braj
– Braj, Commented Nov 7, 2014 at 16:23

Community · Accepted Answer · 2017-05-23 10:33:41Z

3

Through regex and regex ony. The anchor \G matches at the position where the previous match ended.

String s = "ID Number: 4D:9B:C4";
System.out.println(s.replaceAll("(?:ID Number: ([A-Z0-9]{2})|(?<!^)\\G):?([A-Z0-9]{2})","$1 $2"));

Output:

4D 9B C4

Another example with many number of colon separated parts.

String s = "ID Number: 4D:9B:C4:B5:C6:D7:F8:K9";
System.out.println(s.replaceAll("(?:ID Number: ([A-Z0-9]{2})|(?<!^)\\G):?([A-Z0-9]{2})","$1 $2"));

Output:

4D 9B C4 B5 C6 D7 F8 K9

References:

Update:

String s = "We got some text up here\n" +
           "ID Number: 4D:9B:C4:D4:F4\n" +
           "And also some text down here";
System.out.println(s.replaceAll("(?s)(?:ID Number: ([A-Z0-9]{2})|(?<!^)\\G):?([A-Z0-9]{2})|.*?(?=ID Number:)|.+","$1 $2").trim());

edited May 23, 2017 at 10:33

CommunityBot

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answered Nov 7, 2014 at 16:32

Avinash Raj

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5 Comments

user2150250 Over a year ago

Thanks so much for your great answer. Could you please review my edits above and modify or expand your answer to fit the exact nature of my problem?

user2150250 Over a year ago

It seems to only be affecting the one line in question and still outputting the other lines. My output is like ... We got some text up here 4D 9B C4 And also some text down here

user2150250 Over a year ago

I can't seem to put hard returns or fancy formatting in the comment, but imagine in the output I stated in the previous comment that the spaces between "here 4D" and "C4 And" are actually hard returns

user2150250 Over a year ago

Nevermind, I had an error in my copy to my code. I am still getting a leading whitespace in my output though. How do we lop that off?

Avinash Raj Over a year ago

Use trim function to remove the leading spaces.

Robert · Accepted Answer · 2014-11-07 16:31:34Z

1

I suggest using capture groups to actually get what you're interested in. There's no reason not to be repetitive.

String idNum = idNum.replaceAll(
   "ID Number: ([A-Z0-9]{2}):([A-Z0-9]{2}):([A-Z0-9]{2})",
   "$1 $2 $3"
);

answered Nov 7, 2014 at 16:31

Robert

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Comments

fge · Accepted Answer · 2014-11-07 16:24:02Z

0

You can use a lookahead. And since you will probably use this pattern more than once, create it as a static final variable:

private static final Pattern PATTERN = Pattern.compile(":(?=[A-Z0-9]{2})");

// ...

idNum = PATTERN.matcher(idNum).replaceAll(" ");

answered Nov 7, 2014 at 16:24

fge

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Comments

Andreas Gnyp · Accepted Answer · 2014-11-07 16:26:09Z

0

Providing the String schema doesn't change too much, I'd go with

String str = "ID Number: 4D:9B:C4"
numbers = str.split(':')[1].split(':')

Then you might have to .trim() your elements of the array 'numbers'.

After you can go with concatenating numbers[0-2] with spaces inbetween.

answered Nov 7, 2014 at 16:26

Andreas Gnyp

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