Regular Expression

We'll say that a "triple" in a string is a char appearing three times in a row. Return the number of triples in the given string. The triples may overlap.

countTriple("abcXXXabc") → 1
countTriple("xxxabyyyycd") → 3
countTriple("a") → 0

Solution:

public int countTriple(String str) {
  int count = 0;
  int i = 0;
  int len = str.length();
  while (i<len-2) {
    if(str.substring(i,i+3).matches("(.)\\1\\1")) {
      count++;
    }
    i++;
  }
  return count;
}