新建BaseDao

import java.sql.Connection;    import java.sql.DriverManager;    import java.sql.ResultSet;    import java.sql.SQLException;    import java.sql.Statement;        public class BaseDao {        Connection con = null;        Statement st = null;        ResultSet rs = null;            /**        * 获得联接        *         * @return        */        public Connection getConnection() {            try {                // 加载驱动，这一句也可写为：Class.forName("com.mysql.jdbc.Driver");                 Class.forName("com.mysql.jdbc.Driver").newInstance();                    // 建立到MySQL的连接                 con = DriverManager.getConnection("jdbc:mysql://localhost:3306/money_note?characterEncoding=UTF-8", "root", "root");            } catch (Exception e) {                e.printStackTrace();            }            return con;        }            /**        * 关闭数据源        */        public void CloseConnection(Connection con, Statement s, ResultSet rs) {            try {                if (rs != null) {                    rs.close();                }                if (s != null) {                    s.close();                }                if (con != null) {                    con.close();                }            } catch (SQLException e) {                e.printStackTrace();            }        }    }  

import java.sql.Connection;    import java.sql.ResultSet;    import java.sql.SQLException;    import java.sql.Statement;            public class Test extends BaseDao {            Connection con = null;        Statement st = null;        ResultSet rs = null;            /**        * 查询数据        */        public void find() {            con = getConnection();  // 获得联接            try {                st = con.createStatement();                rs = st.executeQuery("select * from app_user");                while (rs.next()) {                    System.out.println("编号：" + rs.getInt("uuid") + ", 姓名：" + rs.getString("userName") + ", 性别：" + rs.getString("sex") + ", 生日：" + rs.getString("birthday") + ", 住址：" + rs.getString("address"));                }            } catch (SQLException e) {                e.printStackTrace();            } finally {                CloseConnection(con, st, rs);   // 关闭联接            }        }            /**        * 添加数据        */        public void add() {            con = getConnection();            try {                st = con.createStatement();                int result = st.executeUpdate("insert into app_user(userName,passWord,sex,birthday,address) values('赵丽颖','wanying','女','1992-02-03','北京市')");                if (result > 0) {                    System.out.println("插入成功");                } else {                    System.out.println("插入失败");                }            } catch (SQLException e) {                System.out.println("插入失败");                e.printStackTrace();            } finally {                CloseConnection(con, st, rs);            }        }            /**        * 更新数据        */        public void update() {            con = getConnection();            try {                st = con.createStatement();                int result = st.executeUpdate("update app_user set address = '河南' where uuid = '3'");                if (result > 0) {                    System.out.println("更新成功");                } else {                    System.out.println("更新失败");                }            } catch (SQLException e) {                e.printStackTrace();            } finally {                CloseConnection(con, st, rs);            }        }            /**        * 删除数据        */        public void delete() {            con = getConnection();            try {                st = con.createStatement();                int result = st.executeUpdate("delete from app_user where uuid = '3'");                if (result > 0) {                    System.out.println("删除成功");                } else {                    System.out.println("删除失败");                }            } catch (SQLException e) {                e.printStackTrace();            } finally {                CloseConnection(con, st, rs);            }        }            public static void main(String[] args) {            Test test = new Test();            //test.add();            // test.update();             test.delete();            test.find();            }        }