总共分为两块：db连接基础方法+业务调用方使用
1、db连接基础方法
public class DemoForWrite {
    static String URL = "jdbc:mysql://127.0.0.1:3306/user";
    static String USER_NAME = "root";
    static String PASSWORD = "123456";

    public static int modify(String sql, List<Object> params) {
        try (Connection connection = DriverManager.getConnection(URL, USER_NAME, PASSWORD);

             PreparedStatement statement = connection.prepareStatement(sql)) {
            for (int i = 0; i < params.size(); i++) {
                statement.setObject(i + 1, params.get(i));
            }

            return statement.executeUpdate();
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
}

sql也可以分离出来 
/**
    String sql = "update tb_user set name=?,age=? where id=?";
    List<Object> params = Lists.newArrayList();
    params.add("hehehehe");
    params.add(67);
    params.add(5);
 */

            
2、业务调用方

public class DemoForWriteApp {
    public static void main(String[] args) {
        // testInsert();
        // testUpdate();
        testDelete();
    }

    private static void testDelete() {
        String sql = "delete from tb_user where id=?";
        List<Object> params = Lists.newArrayList();
        params.add(7);

        int rows = DemoForWrite.modify(sql, params);
        System.out.println("rows = " + rows);
    }

    private static void testUpdate() {
        String sql = "update tb_user set name=?,age=? where id=?";
        List<Object> params = Lists.newArrayList();
        params.add("hehehehe");
        params.add(67);
        params.add(5);

        int rows = DemoForWrite.modify(sql, params);
        System.out.println("rows = " + rows);
    }

    private static void testInsert() {
        String sql = "insert into tb_user(name,age) values(?,?)";
        List<Object> params = Lists.newArrayList();
        params.add("xixihaha");
        params.add(34);
        int rows = DemoForWrite.modify(sql, params);
        System.out.println("rows = " + rows);
    }
}

jdbc-db连接和业务调用方发分离