code: public FormattedStringBuilder fillOrCut(int newLength, char c) {
          if (newLength < 0) {
              throw new IllegalArgumentException();
          }
          int lineStart = _delegate.lastIndexOf(NL);
          if (lineStart == -1) {
              lineStart = 0;
          } else {
              lineStart += NL.length();
          }
          int lineLen = _delegate.length() - lineStart;
  
          if (newLength < lineLen) {
              _delegate = new StringBuilder(_delegate.substring(0, lineStart + newLength));
              return this;
          }
          return fill(newLength, c);
      }
docs: Attempts to append <tt>c</tt> until the line gets the length <tt>
  newLength</tt>. If the line is already longer than <tt>newLength</tt>,
  then the internal strings is cut to <tt>newLength</tt>.
  @param newLength New length of the last line.
  @param c Character to append.
  @return The updated instance of FormattedStringBuilder.