Agent API

public TextStringBuilder append(final String str, final int startIndex, final int length) {
    if (str == null) {
      return appendNull();
    }
    if (startIndex < 0 || startIndex > str.length()) {
      throw new StringIndexOutOfBoundsException("startIndex must be valid");
    }
    if (length < 0 || (startIndex + length) > str.length()) {
      throw new StringIndexOutOfBoundsException("length must be valid");
    }
    if (length > 0) {
      final int len = length();
      ensureCapacity(len + length);
      str.getChars(startIndex, startIndex + length, buffer, len);
      size += length;
    }
    return this;
  }

  /**
   * Calls {@link String#format(String, Object...)} and appends the result.
   *
   * @param format the format string
   * @param objs   the objects to use in the format string
   * @return {@code this} to enable chaining
   * @see String#format(String, Object...)
   */
  public TextStringBuilder append(final String format, final Object... objs) {