想要做好组件 心一定要细, 例如ScrpllPane得右下角Component 都要对着渐变一下.
但一定要首先判断 用户是否设置了右下角Component 
if (scrollPane.getCorner(ScrollPaneConstants.LOWER_RIGHT_CORNER) == null) {
            Component component = new JLabel("") {
                @Override
                protected void paintComponent(Graphics g) {
                    Graphics2D g2 = (Graphics2D) g;
                    Paint oldPaint = g2.getPaint();
                    Rectangle bounds = getBounds();
                    Paint backgroupRectPaint = new GradientPaint(0, 0, new Color(216, 216, 216),
                            bounds.width, bounds.height, new Color(152, 152, 152));
                    g2.setPaint(backgroupRectPaint);
                    g2.fillRect(0, 0, bounds.width, bounds.height);
                    g2.setPaint(oldPaint);
                }
            };
            scrollPane.setCorner(ScrollPaneConstants.LOWER_RIGHT_CORNER, component);
        }
在代码里附带了中文注释.详细可以下载代码看,
下载地址:
ScrollBarDemo