title: get value from jtable
body: <p>I have a jtable and I want the user to fill its cells then i get what he wrote!
  the problem is when i try getValueAt(row index,col index ) the programe give me null , and i am sure that the cell i choose has a value .
   following show how i create the table</p>
  
  <pre><code>String s = JOptionPane.showInputDialog(null, "Enter number of rows");
      int row = Integer.parseInt(s);
      Vector v = new Vector();
      v.add("URL");
      DefaultTableModel Dm = new DefaultTableModel(v, row);
      jTable1.setModel(Dm);
  </code></pre>