public class DBUtil {    Connection conn = null;    Statement stmt = null;    PreparedStatement ps = null;    ResultSet rs = null;    String url = null;    String user = null;    String password = null;    String sql = null;    int number;    public  void openDb() {        try {            Class.forName("com.mysql.jdbc.Driver"); //        } catch (ClassNotFoundException e) {            System.out.println("");            e.printStackTrace();//        }        try {            url = "jdbc:mysql://localhost:3306/db";                user = "root";            password = "root";            conn = DriverManager.getConnection(url, user, password);        } catch (SQLException e) {            System.out.println("驱动加载异常");            e.printStackTrace();        }    }    public ResultSet query(String sql){        try {            stmt = conn.createStatement();            rs = stmt.executeQuery(sql);        } catch (SQLException e) {            System.out.println("sql查询语句异常");            e.printStackTrace();        }        return rs;    }                public Boolean insert(String sql){        boolean boo=false;        try {            stmt = conn.createStatement();            stmt.executeUpdate(sql);// 执            boo=true;        } catch (SQLException e) {            System.out.println("插入语句异常");            e.printStackTrace();        }        return boo;    }

public void closeDb() {                          try {                    if (rs != null) {                        rs.close();                        rs = null;                    }                    if (stmt != null) {                        stmt.close();                        stmt = null;                    }                    if (conn != null) {                        conn.close();                        conn = null;                    }                } catch (Exception e) {                    System.out.println("sql连接关闭异常");                    e.printStackTrace();                }    }}