code: public StrBuilder appendln(final char[] chars, final int startIndex, final int length) {
          return append(chars, startIndex, length).appendNewLine();
      }
docs: Appends a char array followed by a new line to the string builder.
  Appending null will call {@link #appendNull()}.
  
  @param chars  the char array to append
  @param startIndex  the start index, inclusive, must be valid
  @param length  the length to append, must be valid
  @return this, to enable chaining
  @since 2.3