code: private int numOfTabs(String line) {
          int i = 0;
          while (i < line.length() && '\t' == line.charAt(i)) {
              i++;
          }
          return i;
      }
docs: Counts the number of tabs in the line.
  
  @param line the string of the each line of file
  @return the number of tabs at the beginning of the line