How do I use Java Regex to find all repeating character sequences in a string?

Question

Parsing a random string looking for repeating sequences using Java and Regex.

Consider strings:

aaabbaaacccbb

I\'d like to find a regular expression

Answer 1

You can use this positive lookahead based regex:

((\\w)\\2+)(?=.*\\1)

Code:

String elem = "aaabbaaacccbb";
String regex = "((\\w)\\2+)(?=.*\\1)";
Pattern p = Pattern.compile(regex);
Matcher matcher = p.matcher(elem);
for (int i=1; matcher.find(); i++)
System.out.println("Group # " + i + " got: " + matcher.group(1));

OUTPUT:

Group # 1 got: aaa
Group # 2 got: bb