A program has a little bug,let us solve it

Question

compiler and run codes,you must see a bug,can you solve it?
import javax.swing.*;
import javax.swing.table.*;
import java.awt.*;
import java.util.Vector;
public class TestTable extends JFrame{
    static{
            String laf=UIManager.getSystemLookAndFeelClassName();
     try{
            UIManager.setLookAndFeel(laf);
        }catch(Exception exc){}
    Vector columnNames=new Vector();
    Vector data=new Vector();
    Vector part=new Vector();
   JTable table=null;
   public TestTable(){
      columnNames.add("fruit");
      columnNames.add("boolean");
      part.add("Applets");
      part.add(new Boolean(true));
      data.add(part);
      part.add("Oranges");
      part.add(new Boolean(false));
      data.add(part);
      table=new JTable(new MyModel());
      JScrollPane scroll=new JScrollPane(table);
      Container cp=getContentPane();
      cp.add(scroll);
      this.setSize(300, 200);
      this.setVisible(true);
      this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   class MyModel extends AbstractTableModel{
    int rowCount, columnCount;        
    public MyModel(){
        rowCount=data.size();
        columnCount=columnNames.size();
    public String getColumnName(int col) {
        return (String)columnNames.elementAt(col);
    public Class getColumnClass( int col) {
        return getValueAt(0, col).getClass();
    public int getColumnCount() {
        return columnCount;
    public int getRowCount() {
        return rowCount;
    public boolean isCellEditable(int row, int col) {
        return true;
    public void setValueAt(Object obj, int row, int col) {
         ((Vector)data.elementAt(row)).setElementAt(obj,col);
         fireTableCellUpdated(row, col);
    public Object getValueAt(int row, int col) {
        Vector vec=(Vector)data.elementAt(row);
        Object obj=vec.elementAt(col);
        return obj;
   public static void main(String[] args){
     new TestTable();
}

Answer 1

      part.add("Applets");
      part.add(new Boolean(true));
      data.add(part);
      part.add("Oranges");
      part.add(new Boolean(false));
      data.add(part);id say, rethink this piece. but since u kindly said "let us solve it", ill leave the rest to you.
i also dont know if a Vector is really needed here. its synchronized nature is needed if several threads access it parallel, but here an ArrayList would be faster id say.