Java Programming

How to create a JTable with using constructor JTable(Vector,Vector) ?
Were is mistake ?

import javax.swing.*;
import java.awt.*;
import java.util.*;

public class Demo2 extends JFrame {
    JTable table;
    JScrollPane jsp;
    Vector data,colHeads;
    
    Demo2(){
        Container content = getContentPane();
        data = new Vector();
        colHeads = new Vector();
        
        for(int i = 0; i < 15; i++)
            data.add(Integer.toString(i));
        
        for(int i = 0; i < 5; i++)     
          colHeads.add(Integer.toString(i));
      
        content.setLayout(new FlowLayout());
        table = new JTable(data,colHeads);
        jsp = new JScrollPane(table);
        
        content.add(jsp);
        
        setSize(800,600);
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        
    }
   
    public static void main(String[] args) {
        new Demo2();
    }
}

Why ?
Message:
Exception in thread "main" java.lang.ClassCastException: java.lang.String
at javax.swing.table.DefaultTableModel.justifyRows(DefaultTableModel.java:242)
at javax.swing.table.DefaultTableModel.setDataVector(DefaultTableModel.java:198)
at javax.swing.table.DefaultTableModel.<init>(DefaultTableModel.java:133)
at javax.swing.JTable.<init>(JTable.java:451)
at Demo2.<init>(Demo2.java:22)
at Demo2.main(Demo2.java:34)