圆角JButton按钮，雕虫小技，新人可参考

其实可以用以下代码来设置风格，我觉得也挺好看的try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            javax.swing.JOptionPane.showMessageDialog(null, "", "", javax.swing.JOptionPane.ERROR_MESSAGE);
        } catch (InstantiationException ex) {
            javax.swing.JOptionPane.showMessageDialog(null, "", "", javax.swing.JOptionPane.ERROR_MESSAGE);
        } catch (IllegalAccessException ex) {
            javax.swing.JOptionPane.showMessageDialog(null, "", "", javax.swing.JOptionPane.ERROR_MESSAGE);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            javax.swing.JOptionPane.showMessageDialog(null, "", "", javax.swing.JOptionPane.ERROR_MESSAGE);
        }