Matching three or more identical characters - Java program

Asked Aug 30 '17 at 13:22

Active Aug 30 '17 at 13:24

Viewed 70 times

I'm trying to match cases where a sequence of characters contains three or more identical characters in any position, as shown in the following code:

class TRY {
    public static void main(String[] args) {
      String a = "aaaam";
      String b = "aacccccccc";
      String c = "aaffffkb";
      if (b.matches("([a-zA-Z0-9])\\1+"))
          System.out.println("Matches!"); // Display the string.
    }
}

There are many other questions online that suggest using a regular expression like ([a-zA-Z0-9])\\1+ ; "([a-z\\d])\\1{3,}" ; or "([a-z\\d])\\1\\1". The [a-zA-Z0-9] should match any character, and the \\1 should reference the matched character. However none of these match any of my strings, and I don't understand why.

edited Aug 30 '17 at 13:24

Youcef LAIDANI

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asked Aug 30 '17 at 13:22

Alessandro

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create pattern and use `find` – Pavneet_Singh Aug 30 '17 at 13:24
`".*([a-zA-Z0-9])\\1{2}.*"` – Avinash Raj Aug 30 '17 at 13:24
what is the expected output of each input? – Youcef LAIDANI Aug 30 '17 at 13:25
The output should just be a yes or no. I also tried with matcher.matches() and it doesn't work. String.matches() behaves in the same way as Matcher, so I just assumed that the error was in the regex. – Alessandro Aug 30 '17 at 13:30
@Wiktor Stribiżew i tried to propose a solution using replaceAll with one of the OP's regex you can check my solution here [ideone](https://ideone.com/J7o2lD) is it a correct one or it is better to use [pattern](https://stackoverflow.com/questions/8923398/regex-doesnt-work-in-string-matches) like the duplicate question? – Youcef LAIDANI Aug 30 '17 at 13:37
@YCF_L No need for work arounds, `Pattern#find()` is the easiest way. – Wiktor Stribiżew Aug 30 '17 at 13:39

Matching three or more identical characters - Java program

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