JTextPane text = new JTextPane(){
                @Override
                public boolean getScrollableTracksViewportWidth() {
                    return (getSize().width < getParent().getSize().width);
                }

                @Override
                public void setSize(Dimension d) {
                    if (d.width < getParent().getSize().width) {
                        d.width = getParent().getSize().width;
                    }
                    super.setSize(d);
                }
            };