// 一段实现paintBorder（）方法代码
protected void paintBorder(Graphics g) {
   switch(getBorderType()) {
      case LINE_BORDER:   paintLineBorder(g);
                          break;
      case ETCHED_BORDER: paintEtchedBorder(g);
                          break;
      case TITLED_BORDER: paintTitledBorder(g);
                          break;
      ...
   }
}

// Swing中paintBorder()方法的源代码
protected void paintBorder(Graphics g) {
   Border border = getBorder();
   if (border != null) {
      border.paintBorder(this, g, 0, 0, getWidth(), getHeight());
   }
}

...
private Border border;
...
public void setBorder(Border border) {
   Border oldBorder = this.border;
   this.border = border;
   firePropertyChange("border", oldBorder, border);
   if (border != oldBorder) {
      if (border == null || oldBorder == null || !(border.getBorderInsets(this).
                                    equals(oldBorder.getBorderInsets(this)))) {
         revalidate();
      }       
      repaint();
   }
}
...
public Border getBorder() {
   return border;
}

// Test.java
import javax.swing.*;
import javax.swing.border.*;
import java.awt.*;
import java.awt.event.*;
public class Test extends JFrame {
   public static void main(String[] args) {
      JFrame frame = new Test();
      frame.setBounds(100, 100, 500, 200);
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.show();
   }
   public Test() {
      super("实现一个新的边框类型");
      Container contentPane = getContentPane();
      JPanel[] panels = { new JPanel(), 
                     new JPanel(), new JPanel() };
      Border[] borders = { new HandleBorder(),
                     new HandleBorder(Color.red, 8),
                     new HandleBorder(Color.blue, 10) };
      contentPane.setLayout(
               new FlowLayout(FlowLayout.CENTER,20,20));
      for(int i=0; i < panels.length; ++i) {
         panels[i].setPreferredSize(new Dimension(100,100));
         panels[i].setBorder(borders[i]);
         contentPane.add(panels[i]);
      }
   }
}

// 下面的代码截取自javax.swing.border.EtchedBorder
public void paintBorder(Component component, Graphics g, int x, int y, 
                         int width, int height) {
   int w = width;
   int h = height;
   g.translate(x, y);
   g.setColor(etchType == LOWERED? getShadowColor(component) : 
getHighlightColor(component));
   g.drawRect(0, 0, w-2, h-2);
   g.setColor(etchType == LOWERED? getHighlightColor(component) : 
getShadowColor(component));
   g.drawLine(1, h-3, 1, 1);
   g.drawLine(1, 1, w-3, 1);
   g.drawLine(0, h-1, w-1, h-1);
   g.drawLine(w-1, h-1, w-1, 0);
   g.translate(-x, -y);
}