Problem I can not insert in java

I created two classes a connection for the BD and another Insumo that will have an insert method. I execute the code but nothing happens. I think it's class Conexion I'm not sure you could look at the code to see what the problem is

Click of the button

private void btn_ingresarMouseClicked(java.awt.event.MouseEvent evt){                                          
    Insumo obj= new Insumo();
    obj.setUsuario(txtrut.getText());
    obj.setPass(jPasswordField1.getText());
    try {
        obj.insertar();
    }
    catch(SQLException e){
        System.out.println(e.getMessage());
    }
}  

Class Conexion

public class Conexion {
    public static Connection con = null;

    public Connection Conectarse(){
        try {
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            System.out.println("Registro exitoso");
            Connection con = DriverManager.getConnection(
        "jdbc:mysql://localhost:3306/ropa_trabajo?"
        + "user=root&password=");
        } catch (Exception e) {
            System.out.println(e.toString()+"dsgdsh");
        }
        return con;
    }

    public void cerrar() throws SQLException {
        if(con!=null){
            con.close();
        }
    }
}

Class Insumo .

The input class I think is where the problem is

public class Insumo extends Conexion {
    private String usuario;
    private String pass;

    public Insumo(){
        super();
        con=super.Conectarse();
    }

    public void insertar() throws SQLException{
        String sql="INSERT INTO usuario(4,?,?)";
        PreparedStatement sentencia=super.Conectarse().prepareStatement(sql);
        sentencia.setString(1,getUsuario());
        sentencia.setString(2,getPass());
        sentencia.executeUpdate();
        super.cerrar();
    }

    /**
     * @return the usuario
     */
    public String getUsuario() {
        return usuario;
    }

    /**
     * @param usuario the usuario to set
     */
    public void setUsuario(String usuario) {
        this.usuario = usuario;
    }

    /**
     * @return the pass
     */
    public String getPass() {
        return pass;
    }

    /**
     * @param pass the pass to set
     */
    public void setPass(String pass) {
        this.pass = pass;
    }
}