How to check for repeating sequence in an integer

Question

I have an alpha-numeric string and I want to check for pattern repetition in it just for the integers. And they should be continuous.

Example

Answer 1

You can take help of regex to solve this I think. Consider code like this:

String arr[] = {"12341234abc", "1234foo1234", "12121212", "111111111", "1a1212b123123c12341234d1234512345"};
String regex = "(\\d+?)\\1";
Pattern p = Pattern.compile(regex);
for (String elem : arr) {
    boolean noMatchFound = true;
    Matcher matcher = p.matcher(elem);
    while (matcher.find()) {
        noMatchFound = false;
        System.out.println(elem + " got repeated: " + matcher.group(1));
    }
    if (noMatchFound) {
        System.out.println(elem + " has no repeation");
    }
}

OUTPUT:

abc12341234abc got repeated: 1234
1234foo1234 has no repeation
12121212 got repeated: 12
12121212 got repeated: 12
111111111 got repeated: 1
111111111 got repeated: 1
111111111 got repeated: 1
111111111 got repeated: 1
1a1212b123123c12341234d1234512345 got repeated: 12
1a1212b123123c12341234d1234512345 got repeated: 123
1a1212b123123c12341234d1234512345 got repeated: 1234
1a1212b123123c12341234d1234512345 got repeated: 12345

Explanation:

Regex being used is (\\d+?)\\1 where

\\d        - means a numerical digit
\\d+       - means 1 or more occurrences of a digit
\\d+?      - means reluctant (non-greedy) match of 1 OR more digits
( and )    - to group the above regex into group # 1
\\1        - means back reference to group # 1
(\\d+?)\\1 - repeat the group # 1 immediately after group # 1