Given a string and a non-empty substring sub, compute recursively the largest substring which starts and ends with sub and return its length.

Given a string and a non-empty substring sub, compute recursively the largest substring which starts and ends with sub and return its length.

strDist("catcowcat", "cat") → 9
strDist("catcowcat", "cow") → 3
strDist("cccatcowcatxx", "cat") → 9

public int strDist(String str, String sub) {

  int strLen = str.length();
  int subLen = sub.length();
  if(strLen<subLen)
  {
    return 0;
  }
  if(str.substring(0,subLen).equals(sub))
  {
    if(str.substring(strLen-subLen,strLen).equals(sub))
    {
      return strLen;
    }
    else
    {
      return  strDist(str.substring(0,strLen-1),sub);
    }
  }
  else
  {
    return  strDist(str.substring(1,strLen),sub);
  }
}