做JList时能编译但运行报空指向，请教各位大哥们

Question

/*
 * FontTest.java
 *
 * Created on 2006年8月17日, 下午9:37
 */package accp.test;import java.awt.Font;
import java.awt.GraphicsEnvironment;
import javax.swing.DefaultListModel;/**
 *
 * @author  yll
 */
public class FontTest extends javax.swing.JFrame {
    
    /** Creates new form FontTest */
    public FontTest() 
    {
        fontStyle();
        fontSizeShow();
        initComponents();
    }
    
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    // <editor-fold defaultstate="collapsed" desc=" 生成的代码 ">
    private void initComponents()
    {
        txtShow = new javax.swing.JTextField();
        jScrollPane1 = new javax.swing.JScrollPane();
        lstFontSize = new javax.swing.JList(/*fontSize*/);
        jScrollPane2 = new javax.swing.JScrollPane();
        lstFontStyle =  new javax.swing.JList(/*fontName*/);        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        txtShow.setText("\u9f99\u864e\u4e89\u6597\uff01");        DefaultListModel dm=new DefaultListModel();
        this.lstFontSize.setModel(dm);
        dm.add(0,fontSize);
        lstFontSize.addListSelectionListener(new javax.swing.event.ListSelectionListener()
        {
            public void valueChanged(javax.swing.event.ListSelectionEvent evt)
            {
                lstFontSizeValueChanged(evt);
            }
        });        jScrollPane1.setViewportView(lstFontSize);        DefaultListModel dl=new DefaultListModel();
        this.lstFontStyle.setModel(dl);
        dl.add(0,fontName);
        lstFontStyle.addListSelectionListener(new javax.swing.event.ListSelectionListener()
        {
            public void valueChanged(javax.swing.event.ListSelectionEvent evt)
            {
                lstFontStyleValueChanged(evt);
            }
        });        jScrollPane2.setViewportView(lstFontStyle);        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .add(28, 28, 28)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(layout.createSequentialGroup()
                        .add(jScrollPane1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 70, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                        .add(77, 77, 77)
                        .add(jScrollPane2, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 82, Short.MAX_VALUE))
                    .add(txtShow, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 229, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(38, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(txtShow, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 49, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(jScrollPane2, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 167, Short.MAX_VALUE)
                    .add(jScrollPane1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 167, Short.MAX_VALUE))
                .add(29, 29, 29))
        );
        pack();
    }// </editor-fold>    private void lstFontStyleValueChanged(javax.swing.event.ListSelectionEvent evt)
    {
        Font f=this.txtShow.getFont();
        Font newFont=new Font(this.lstFontStyle.getSelectedValue().toString(),f.getStyle(),f.getSize());
        this.txtShow.setFont(newFont);
        
    }    private void lstFontSizeValueChanged(javax.swing.event.ListSelectionEvent evt)
    {
        Font f=this.txtShow.getFont();
        Font newFont=new Font(f.getName(),f.getStyle(),Integer.parseInt(this.lstFontSize.getSelectedValue().toString()));
        this.txtShow.setFont(newFont);
    }
    private void fontStyle()
    {
        GraphicsEnvironment ge=GraphicsEnvironment.getLocalGraphicsEnvironment();
        this.fontName=ge.getAvailableFontFamilyNames();
        
    }
   private void fontSizeShow()
    {
        int j=2;
        for( int i=0;i<10;i++)
        {
            
            this.fontSize[i]=String.valueOf(j);
            j+=2;
            
        }
        
    }
    
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new FontTest().setVisible(true);
            }
        });
    }
    
    // 变量声明 - 不进行修改
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JList lstFontSize;
    private javax.swing.JList lstFontStyle;
    private javax.swing.JTextField txtShow;
    // 变量声明结束
    private String [] fontName;
    private String [] fontSize;
}