CODEWITHSUNDEEP
regex
Jack Cassidy
Jack Cassidy

Reputation: 159

Java Regex Identifying Non-Consecutive Pairs of Characters/Numbers

I'm looking to pick out pairs of word characters in a string, that may not necessarily be beside each other in the string. For example, "ahna32g" should match, due to the pair of 'a' characters. What I currently have is "\w*(\w)\1+\w*" which is successful if the matching characters are consecutive. I'm quite new to regular expressions, so if a detailed explanation could be given I'd really appreciate it.

Upvotes: 1

Views: 743

Answers (2)

linden2015
linden2015

Reputation: 887

My approach captures the (earliest) repeated characters in group 1 and 2. It's also less steps than the already posted answer.

\w*?(\w)(?=\w*?(\1))\w*

\w*? // 0 or more word chars, lazily matched
(\w) // a word char (as group 1)
(?=  // look ahead and assert a match of:
\w*? // 0 or more word chars, lazily matched
(\1) // group 1 (as group 2)
)    // end of assertion
\w*  // 0 or more word chars
  • Flags: g

Demo

Upvotes: 0

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 627327

You need to insert \w* between (\w) and \1 to let the regex engine match any 0+ word chars in between the repeating chars:

\w*(\w)\w*\1+\w*
       ^^^

See the regex demo.

So, the regex will match

  • \w* - 0+ word chars
  • (\w) - capture a word char into Group 1
  • \w* - will match 0+ word chars
  • \1+ - one or more occurrences of the value inside Group 1
  • \w* - 0+ word chars.

Upvotes: 2

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