Alguem pode me ajudar nao consigo inserir dados

import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.sql.*;

public class cadcli extends JFrame 
 
 { 
	private JButton bbuscar;
	private JButton blimpar;
	private JButton bgravar;
	
	private JTextField tbuscar;
	private JTextField t1;
	private JTextField t2;
	private JTextField t3;
	private JTextField t4;
	private JTextField t5;

	private JLabel lbuscar;
	private JLabel l6;	
	private JLabel l1;
	private JLabel l2;
	private JLabel l3;
	private JLabel l4;
	private JLabel l5;
	
	private Icon carro;
	private Connection conn;
	

       public cadcli()
 	   {
		super("CADASTRO DE CLIENTE"); 
		Container ct = getContentPane(); 
		ct.setLayout(null); 
		
	try
         {
	   
	   			Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
		 }
		 	catch (ClassNotFoundException e)
        		{
        	    JOptionPane.showMessageDialog(null,"Driver nao encontrado ");
        		}
		try
		 {
            String data = "jdbc:odbc:bd";
		 	Connection conn = DriverManager.getConnection(data,"","");
	   			
		 }catch (Exception sqlEx)
		 {
		 	JOptionPane.showMessageDialog(null,"Conexao falhou");	
		 }
		
						
				
		l2 = new JLabel ("NOME");
		l2.setBounds(10,85,100,20);
		ct.add(l2);	
		
		t1 = new JTextField("");
		t1.setBounds(80,85,250,20);
		ct.add(t1);	
		          
		
		blimpar = new JButton("LIMPAR");
		blimpar.setBounds(10,230,100,20);
		ct.add(blimpar);		

		bgravar = new JButton("GRAVAR");
		bgravar.setBounds(225,230,100,20);
		bgravar.addActionListener(
			new ActionListener () {
				public void actionPerformed( ActionEvent event)
				{
					try
						{
						PreparedStatement st = conn.prepareStatement("Select Nome from cliente where Nome = ?");
						st.setString(1,t1.getText());
						ResultSet rs = st.executeQuery();
						if (rs.next())
							{
							JOptionPane.showMessageDialog(null,"Este codigo ja existe");
							}
						else
							{
							PreparedStatement vs = conn.prepareStatement("insert into Cliente values (?)");
							vs.setString(1,t1.getText());
							vs.executeUpdate();
							JOptionPane.showMessageDialog(null,"Dado inserido com exito!");
							}
						rs.close();
				} catch(Exception sqlEX) {JOptionPane.showMessageDialog(null,"Dado nao inserido!");}
				
				limpar();
				}
				}
			
		
			);
		ct.add(bgravar);
		
		setSize(800,800);
		setVisible(true);
	 
	}	
	
	
			
		
	
	protected void limpar()
	{
		t1.setText (" ");
	
	}
		
	public static void main(String args [])
	
{
		cadcli F = new cadcli();
		F.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}	

}