public int maxBlock(String str) {

  int max = 0;

  for(int i = 0; i < str.length(); i++)
  {
    char c = str.charAt(i);
    int j = i + 1;
    int possibleMax = 1;

    // iterate through a "block"
    while(j < str.length() && str.charAt(j) == c)
    {
      possibleMax++;
      j++;
    }

    // if the block's length is greater than any found, save it
    if(possibleMax > max)
      max = possibleMax;
  }

  return max;
}