Clase Coneccion

    private final String DRIVER = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
    private final String URL =  "jdbc:sqlserver://localhost:1433;databaseName=.....";
    private final String USER = "";
    private final String PASS  = "";

    private Connection cn = null;
    private Statement st = null;

    public void conectar() throws SQLException{
        try {
            Class.forName(DRIVER);
            cn = DriverManager.getConnection(URL, USER, PASS);
        } catch (ClassNotFoundException | SQLException e) {
            System.out.println(e.getMessage());
        }
    }
 
    public void close() throws SQLException{
        this.cn.close();
    }
 
    public int insertar(String insertar) throws SQLException{
        st = (Statement) this.cn.createStatement();
        return st.executeUpdate(insertar);
    }
 
    public void actualizar(String actualizar) throws SQLException{
        st = (Statement) this.cn.createStatement();
        st.executeUpdate(actualizar);
    }
 
    public int borrar(String borrar) throws SQLException{
        st = (Statement) this.cn.createStatement();
        return st.executeUpdate(borrar);
    }
 
    public ResultSet consulta(String consulta) throws SQLException{
        st = (Statement) this.cn.createStatement();
        return this.st.executeQuery(consulta);
    }