JDBC 查询数据练习

package come.hanqi;

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

public class test4 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.println("请选择您要输入的类型：");
        System.out.println(" " + "a:身份证号");
        System.out.println(" " + "b:准考证号");
        String s = sc.next();

        Connection conn = null;
        try
        {
            Class.forName("oracle.jdbc.OracleDriver");
            String url = "jdbc:oracle:thin:@localhost:1521:ORCL";
            conn = DriverManager.getConnection(url, "test1", "574004");
            System.out.println("连接数据库成功");

            Statement st = conn.createStatement();
            if (s.equals("a")) 
            {
                for (int i = 0; i < 9; i++)
                {
                    System.out.println("请输入身份证号：");
                    String ID = sc.next();
                    String IDCard = "select * from EXAMSTUDENT t where idcard=" + ID;
                    ResultSet rs = st.executeQuery(IDCard);

                    if (ID != "select idcard from EXAMSTUDENT t ")
                    {
                        System.out.println("输入有误请重新输入");
                        i--;
                        
                    }
                    while (rs.next()) 
                    {
                        String fl = rs.getString(1);
                        String ty = rs.getString(2);
                        String id = rs.getString(3);
                        String ex = rs.getString(4);
                        String stu = rs.getString(5);
                        String lo = rs.getString(6);
                        String ga = rs.getString(7);

                        System.out.println("flowid=" + fl + ",type=" + ty + "，idcard=" + id + "，examcard=" + ex + "，姓名："
                                + stu + "，籍贯:" + lo + "，分数:" + ga);
                    }

                }

            } 
            else if (s.equals("b"))
            {
                for (int i = 0; i < 9; i++)
                {
                    System.out.println("请输入准考证号：");
                    String EX = sc.next();
                    String EXcard = "select * from EXAMSTUDENT t where examcard=" + EX;
                    ResultSet rs = st.executeQuery(EXcard);

                    if (EX != "select EXAMCARD from EXAMSTUDENT t ")
                    {
                        System.out.println("您输入有误，请重新输入");
                    }
                    while (rs.next()) 
                    {
                        String fl = rs.getString(1);
                        String ty = rs.getString(2);
                        String id = rs.getString(3);
                        String ex = rs.getString(4);
                        String stu = rs.getString(5);
                        String lo = rs.getString(6);
                        String ga = rs.getString(7);

                        System.out.println("flowid=" + fl + ",type=" + ty + "，idcard=" + id + "，examcard=" + ex + "，姓名："
                                + stu + "，籍贯:" + lo + "，分数:" + ga);
                    }
                }
            }
            else 
            {
                System.out.println("您输入有误");
            }

        }
        catch (Exception e)
        {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
            System.out.println("连接数据库失败");
        }

    }

}