java 的scrollpane怎么把他的边界去掉

//声明对象
JTextArea jtaContent = new JTextArea();
JPanel jpMain = new JPanel();
//设置textarea
jtaContent.setBorder(BorderFactory.createLoweredBevelBorder());
jtaContent.setText(null);
//用jtaContent创建JScrollPane对象
JScrollPane scroll = new JScrollPane(jtaContent);
scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED); //水平滚动条根据需要才显示
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED); //垂直滚动条根据需要才显示
scroll.setPreferredSize(new Dimension(300, 200));
//添加到panel
jpMain.add(scroll);