int end = this.undoString.length(); StringContent.this.remove(this.start, end);
undoString = getString(start, len); if (marks != null) positions = getPositionsInRange(null, start, len); remove(this.start, len);
    public void redo()    {      super.redo();      try        {          int end = this.undoString.length();          StringContent.this.remove(this.start, end);        }      catch (BadLocationException bad)        {          throw new CannotRedoException();        }    }