java jdbc方式读写mysql

import java.io.UnsupportedEncodingException;
import java.sql.*;

public class Main {
    public static void main(String[] args) {
        Connection connection = null;
        Connection cnn = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
        }catch (ClassNotFoundException e){
            System.out.println("获取驱动类失败");
            e.printStackTrace();
        }
        try {
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","123456");
            cnn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","123456");

        }catch (SQLException e){
            System.out.println("连接数据库失败");
            e.printStackTrace();
        }
        String sql = "select * from news limit 20";
        try {
            preparedStatement = connection.prepareStatement(sql);
        }catch (SQLException e){
            e.printStackTrace();
        }
        try {
            resultSet = preparedStatement.executeQuery(sql);

        }catch (SQLException e){
            e.printStackTrace();

        }
        try {
            while(resultSet.next())
            {
                //int id = resultSet.getInt("ID_");
                String title = resultSet.getString("contenttitle");
                String content = resultSet.getString("content");

                String sql1="insert into news1(title,content) values(?,?)";
                PreparedStatement pstmt=cnn.prepareStatement(sql1);

                String title_iso88591 = new String(title.getBytes("UTF-8"),"ISO8859-1");
                String title_utf8 = new String(title_iso88591.getBytes("ISO8859-1"),"UTF-8");

                System.out.println(title_utf8);
                pstmt.setString(1, title_utf8);

                String content_iso88591 = new String(content.getBytes("UTF-8"),"ISO8859-1");
                String content_utf8 = new String(content_iso88591.getBytes("ISO8859-1"),"UTF-8");

                System.out.println(content_utf8);
                pstmt.setString(2, content_utf8);

                int res=pstmt.executeUpdate();
                if(res>0){
                    System.out.println("数据录入成功");
                }
                pstmt.close();
                //System.out.println("Content title:"+contenttitle+ "\n" + "content:"+content);
                //System.out.println("id:"+id+" name:"+name+" creator:"+creator);
            }


        }catch (SQLException e){
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        if(resultSet!=null)
        {
            try {
                preparedStatement.close();

            }catch (SQLException e){
                e.printStackTrace();
            }
        }
        if(connection!=null)
        {
            try {
                connection.close();
                cnn.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }
    }
}