}
    return sb.toString();
  }

  /**
   * Returns a string consisting of a specific number of concatenated copies of an input string. For
   * example, {@code repeat("hey", 3)} returns the string {@code "heyheyhey"}.
   *
   * @param string any non-null string
   * @param count the number of times to repeat it; a nonnegative integer
   * @return a string containing {@code string} repeated {@code count} times (the empty string if