课堂实践6-7

实践1

实践2

public class MessageDAO {
    public static String url;
    private String user;
    private String passwd;

    public MessageDAO(String url, String user, String passwd) {
        this.url = url;
        this.user = user;
        this.passwd = passwd;
    }

    public void add(week12.Message message) {
        try(Connection conn = DriverManager.getConnection(url, user, passwd);
            Statement statement = conn.createStatement()) {
            String sql = String.format(
                    "INSERT INTO t_message(name, CountryCode, Distridt,Population) VALUES ('%s', '%s', '%s', '%s')",
                    message.getName(), message.getCountryCode(), message.getDistridt(),message.getPopulation());
            statement.executeUpdate(sql);
        } catch(SQLException ex) {
            throw new RuntimeException(ex);
        }
    }
    public  static week12.Message toMessage(ResultSet result) throws SQLException {
        week12.Message message = new week12.Message();
        message.setId(result.getLong(1));
        message.setName(result.getString(2));
        message.setCountryCode(result.getString(3));
        message.setDistridt(result.getString(4));
        message.setPopulation(result.getString(4));
        return message;
    }

    public static void main(String[] args)    throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");
        String jdbcUrl = "jdbc:mysql://localhost:3306/world";
        String user = "root";
        String passwd = "root";
        try (Connection conn =
                     DriverManager.getConnection(jdbcUrl, user, passwd)) {
            System.out.printf("已%s数据库连接%n", conn.isClosed() ? "关闭" : "打开");
            try (Statement statement = conn.createStatement()) {
                ResultSet result =
                        statement.executeQuery("SELECT * FROM `city` WHERE Population>5000000");
                System.out.println("ID" + "	" + "	" + "Name" + "	" + "	" + "CountryCode" + "	" + "	" + "Distridt" + "	" + "	" + "Population");
                int count = 0;
                while (result.next()) {
                    System.out.print(result.getInt(1) + "	"+"	");
                    System.out.print(result.getString(2) + "	"+"	");
                    System.out.print(result.getString(3) + "	"+"	");
                    System.out.print(result.getString(4) + "	"+"	");
                    System.out.print(result.getString(5) + "	"+"	");
                    System.out.println();
                }
            } catch (SQLException ex) {
                throw new RuntimeException(ex);
            }
        }
    }}

实践三

import java.sql.*;
import java.util.*;

public class MessageDAO {
    public static String url;
    private String user;
    private String passwd;

    public MessageDAO(String url, String user, String passwd) {
        this.url = url;
        this.user = user;
        this.passwd = passwd;
    }

    public void add(Message message) {
        try(Connection conn = DriverManager.getConnection(url, user, passwd);
            Statement statement = conn.createStatement()) {
            String sql = String.format(
                    "INSERT INTO t_message(name, CountryCode, Distridt,Population) VALUES ('%s', '%s', '%s', '%s')",
                    message.getName(), message.getCountryCode(), message.getDistridt(),message.getPopulation());
            statement.executeUpdate(sql);
        } catch(SQLException ex) {
            throw new RuntimeException(ex);
        }
    }
    public  static Message toMessage(ResultSet result) throws SQLException {
        Message message = new Message();
        message.setId(result.getLong(1));
        message.setName(result.getString(2));
        message.setCountryCode(result.getString(3));
        message.setDistridt(result.getString(4));
        message.setPopulation(result.getString(4));
        return message;
    }

    public static void main(String[] args)    throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");
        String jdbcUrl = "jdbc:mysql://localhost:3306/world";
        String user = "root";
        String passwd = "root";
        try (Connection conn =
                     DriverManager.getConnection(jdbcUrl, user, passwd)) {
            System.out.printf("已%s数据库连接%n", conn.isClosed() ? "关闭" : "打开");
            try (Statement statement = conn.createStatement()) {
                ResultSet result =
                        statement.executeQuery("SELECT SUM( Population ) FROM  `city` WHERE District =  'Tokyo'");
                System.out.println("ID" + "	" + "	" + "Name" + "	" + "	" + "CountryCode" + "	" + "	" + "Distridt" + "	" + "	" + "Population");
                int count = 0;
                while (result.next()) {
                    System.out.print(result.getString(1) + "	"+"	");
                    System.out.println();
                }
            } catch (SQLException ex) {
                throw new RuntimeException(ex);
            }
        }
    }}

实践四

import java.sql.*;
import java.util.*;

public class MessageDAO {
    public static String url;
    private String user;
    private String passwd;

    public MessageDAO(String url, String user, String passwd) {
        this.url = url;
        this.user = user;
        this.passwd = passwd;
    }

    public void add(Message message) {
        try(Connection conn = DriverManager.getConnection(url, user, passwd);
            Statement statement = conn.createStatement()) {
            String sql = String.format(
                    "INSERT INTO t_message(LifeExpectancy) VALUES ('%s')",message.getLifeExpectancy()
                    );
            statement.executeUpdate(sql);
        } catch(SQLException ex) {
            throw new RuntimeException(ex);
        }
    }
    public  static Message toMessage(ResultSet result) throws SQLException {
        Message message = new Message();
        message.setLifeExpectancy(result.getString(1));
        return message;
    }

    public static void main(String[] args)    throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");
        String jdbcUrl = "jdbc:mysql://localhost:3306/world";
        String user = "root";
        String passwd = "root";
        try (Connection conn =
                     DriverManager.getConnection(jdbcUrl, user, passwd)) {
            System.out.printf("已%s数据库连接%n", conn.isClosed() ? "关闭" : "打开");
            try (Statement statement = conn.createStatement()) {
                ResultSet result =
                        statement.executeQuery("SELECT * FROM `country` WHERE 1");
                int count = 0;
                Double sum=0.0;
                while (result.next()) {
                    System.out.print( result.getDouble(8)+ "	"+"	");
                    sum=sum+ result.getDouble(8);
                    System.out.println();
                    count++;
                }
                System.out.println(sum/count);
            } catch (SQLException ex) {
                throw new RuntimeException(ex);
            }
        }
    }}