急!请叫高手,一个关于jcombobox的问题

Question

请参看下面代码：package untitled20;import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import com.borland.jbcl.layout.*;
import javax.swing.plaf.basic.BasicComboBoxEditor;
public class Frame1 extends JFrame {
  XYLayout xYLayout1 = new XYLayout();
  JComboBox jComboBox1 = new JComboBox();
  EditorEX  comboboxEditor = new EditorEX();  //Construct the frame
  public Frame1() {
    enableEvents(AWTEvent.WINDOW_EVENT_MASK);
    try  {
      jbInit();
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }  //Component initialization
  private void jbInit() throws Exception  {
    this.getContentPane().setLayout(xYLayout1);
    this.setSize(new Dimension(400, 300));
    this.setTitle("Frame Title");
    this.getContentPane().add(jComboBox1, new XYConstraints(18, 70, 199, 23));
    //------------------------------------------------------------------
    jComboBox1.addItem("测试数据1");
    jComboBox1.addItem("测试数据2");
    jComboBox1.setEditable(true);//必须这这句，否则你看不到所要的效果.
    jComboBox1.setEditor(comboboxEditor);
    comboboxEditor.setBackgroundColor(Color.black);
    comboboxEditor.setForegroundColor(Color.red);    comboboxEditor.addFocusListener(new FocusListener() {
       public void focusGained(FocusEvent e) {
         System.err.println(" get focus");
       }       public void focusLost(FocusEvent e) {
         System.err.println(" lost focus");
       }
    });
  }  //Overridden so we can exit on System Close
  protected void processWindowEvent(WindowEvent e) {
    super.processWindowEvent(e);
    if(e.getID() == WindowEvent.WINDOW_CLOSING) {
      System.exit(0);
    }
  }  class EditorEX extends BasicComboBoxEditor {     public void setBackgroundColor(Color value) {
        editor.setBackground(value);
     }     public void setForegroundColor(Color value) {
        editor.setForeground(value);
     }     public void addFocusListener(FocusListener l) {
        editor.addFocusListener(l);     }  }
}