小程序总结

Posted 2020-07-11 guoDaXia的博客

package com.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;

import com.entity.Student;
import com.util.JDBC;

public class StudentDAO {
    static Connection conn=new JDBC().getConn();
    static PreparedStatement pstml=null;
    static ResultSet rs=null;
    
    public void menu(){
        System.out.println("********学生管理系统********");
        System.out.println("*1. 查询所有学生信息");
        System.out.println("*2. 录入学生信息");
        System.out.println("*3. 删除学生信息");
        System.out.println("*4. 查询单个学生信息");
        System.out.println("*5. 修改学生信息");
        System.out.println("*exit. 退出");
        System.out.println("*help. 帮助");
        System.out.println("****************************");
    }
    
    public int addStudent(Student s) throws SQLException{
        String sql="insert into student(name,sex,age,tel)" +
                "values(?,?,?,?)";
        pstml= conn.prepareStatement(sql);
        //pstml.setInt(1, s.getId());
        pstml.setString(1, s.getName());
        pstml.setString(2, s.getSex());
        pstml.setInt(3, s.getAge());
        pstml.setLong(4, s.getTel());
        return pstml.executeUpdate();    
    }
    
    public int deleteStudent(int id) throws SQLException{
        String sql="delete * from student where id=?";
        pstml= conn.prepareStatement(sql);
        pstml.setInt(1, id);
        return pstml.executeUpdate();
    }
    
    public int change(Student s) throws SQLException{
        String sql="update student set name=?,sex=?,age=?,tel=? where id=?";
        pstml= conn.prepareStatement(sql);
        pstml.setString(1, s.getName());
        pstml.setString(2, s.getSex());
        pstml.setInt(3, s.getAge());
        pstml.setLong(4, s.getTel());
        pstml.setInt(5, s.getId());
        return pstml.executeUpdate();
    }
    
    public Student studentFindById(int id) throws SQLException{
        String sql="select * from student where id=?";
        pstml= conn.prepareStatement(sql);
        pstml.setInt(1, id);
        rs=pstml.executeQuery();
        Student s = null;
        while(rs.next()){
            s=new Student();
            s.setId(rs.getInt("id"));
            s.setName(rs.getString("name"));
            s.setSex(rs.getString("sex"));
            s.setAge(rs.getInt("age"));
            s.setTel(rs.getLong("tel"));
        }
        return s;
    }
    
    public ArrayList<Student> studentFindAll() throws SQLException{
        ArrayList<Student> studentList=new ArrayList<Student>();
        String sql="select * from student";
        pstml= conn.prepareStatement(sql);
        rs=pstml.executeQuery();
        while(rs.next()){
            Student s=new Student();
            s.setId(rs.getInt("id"));
            s.setName(rs.getString("name"));
            s.setSex(rs.getString("sex"));
            s.setAge(rs.getInt("age"));
            s.setTel(rs.getLong("tel"));
            studentList.add(s);
        }
        return studentList;
    }
    
    public static void close() throws SQLException{
        if(conn!=null){
            conn.close();
        }else if(pstml!=null){
            pstml.close();
        }else if(rs!=null){
            rs.close();
        }
    }

}

View Code

package com.entity;

public class Student {
    private int id;
    private String name;
    private String sex;
    private int age;
    private long tel;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public Student() {
        super();
        // TODO Auto-generated constructor stub
    }
    public Student(int id, String name, String sex, int age, long tel) {
        super();
        this.id = id;
        this.name = name;
        this.sex = sex;
        this.age = age;
        this.tel = tel;
    }
    public Student( String name, String sex, int age, long tel) {
        super();
        this.name = name;
        this.sex = sex;
        this.age = age;
        this.tel = tel;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public long getTel() {
        return tel;
    }
    public void setTel(long tel) {
        this.tel = tel;
    }
    
    public String toString(){
        return "Student [id="+getId()+", name="+getName()+", age="+getAge()+", sex="+getSex()+", tel="+getTel()+"]";
    }

}

View Code

package com.test;

import java.util.List;
import java.util.Scanner;

import com.dao.StudentDAO;
import com.entity.Student;

public class StudentManager {
    
    
    
    public static void main(String[] args){
        StudentDAO studentDao = new StudentDAO();
        studentDao.menu();
        Scanner sc = new Scanner(System.in);
        while(true){
            try {
                System.out.print("请输入功能编号：");
                String option = sc.nextLine();
                switch(option){
                    case "1":
                        System.out.println("以下是学生的信息：");
                        List<Student> arr = studentDao.studentFindAll();
                        for(int i=0;i<arr.size();i++){
                            System.out.println(arr.get(i));
                        }
                        System.out.println("总计 "+arr.size()+" 个");
                        break;
                    case "2":
                        while(true){
                            //假设学生年龄在0~80之间
                            System.out.println("请输入学生信息【name#sex#age#tel】或者输入【break】返回上一级目录");
                            String stuStr = sc.nextLine();
                            if(stuStr.equals("break")){
                                break;
                            }                            
                            String[] stuArr = stuStr.split("#");
                            String name = stuArr[0];
                            String sex = stuArr[1];
                            int age = Integer.parseInt(stuArr[2]);
                            Long tel=Long.parseLong(stuArr[3]);
                            Student s=new Student(name,sex,age,tel);
                            if(
                                    name==null||name.equals("")||
                                    sex==null||sex.equals("")||
                                    (((sex.equals("男")||sex.equals("女"))==false)||
                                    age<=0||age>=80||
                                    ((tel>=10000000&&tel<100000000)||( tel>=10000000000l && tel<100000000000l))==false)
                                )
                            {
                                System.out.println("信息格式错误！注意：\\n" +
                                        "1、学生姓名，性别，年龄，电话号码不能为空\\n" +
                                        "2、性别只能为男和女\\n" +
                                        "3、年龄在0~80之间\\n" +
                                        "4、" +
                                        "5、tel为电话号码或者手机号码，必须是8位或者11位数字");
                                continue;
                            }else{
                                int i=studentDao.addStudent(s);
                                if(i>0){
                                    System.out.println("添加成功！");
                                }else{
                                    System.out.println("系统异常，信息添加失败！");
                                }
                            }
                            
                        }
                        
                        break;
                    case "3":
                        while(true){
                            System.out.println("请输入要删除学生的学号或者输入【break】返回上一级目录");
                            String idStr = sc.nextLine();
                            if(idStr.equals("break")){
                                break;//跳出当前循环，返回主菜单
                            }
                            int id = Integer.parseInt(idStr);
                            Student oldStu = studentDao.studentFindById(id);
                            if(oldStu == null){
                                System.out.println("您要删除的学生不存在！");
                                continue;
                            }
                            int i=studentDao.deleteStudent(id);
                            if(i>0){
                                System.out.println("添加成功！");
                            }else{
                                System.out.println("系统异常，信息添加失败！");
                            }
                        }
                        break;
                    case "4":
                        while(true){
                            System.out.println("请输入学号或者输入【break】返回上一级目录");
                            String idStr = sc.nextLine();
                            if(idStr.equals("break")){
                                break;
                            }
                            //1001#terry#12
                            int id = Integer.parseInt(idStr);
                            Student stu = studentDao.studentFindById(id);
                            System.out.println(stu==null?"sorry,not found!":stu);
                        }
                        break;
                    case "5"://修改
                        while(true){
                            System.out.println("请输入要修改学生的学号或者输入【break】返回上一级目录");
                            String idStr = sc.nextLine();
                            if(idStr.equals("break")){
                                break;//跳出当前循环，返回主菜单
                            }
                            int id = Integer.parseInt(idStr);
                            Student oldStu = studentDao.studentFindById(id);
                            if(oldStu == null){
                                System.out.println("您要修改的学生不存在！");
                                continue;
                            }
                            System.out.println("原有信息为："+oldStu);
                            System.out.println("请输入学生信息【name#sex#age#tel】");
                            String stuStr = sc.nextLine();
                            if(stuStr.equals("break")){
                                break;
                            }                            
                            String[] stuArr = stuStr.split("#");
                            int stuId=id;
                            String name = stuArr[0];
                            String sex = stuArr[1];
                            int age = Integer.parseInt(stuArr[2]);
                            Long tel=Long.parseLong(stuArr[3]);
                            Student s=new Student(stuId,name,sex,age,tel);
                            
                            if(
                                    name==null||name.equals("")||
                                    sex==null||sex.equals("")||
                                    (((sex.equals("男")||sex.equals("女"))==false)||
                                    age<=0||age>=80||
                                    ((tel>=10000000&&tel<100000000)||( tel>=10000000000l && tel<100000000000l))==false)
                                )
                            {
                                System.out.println("信息格式错误！注意：\\n" +
                                        "1、学生姓名，性别，年龄，电话号码不能为空\\n" +
                                        "2、性别只能为男和女\\n" +
                                        "3、年龄在0~80之间\\n" +
                                        "4、" +
                                        "5、tel为电话号码或者手机号码，必须是8位或者11位数字");
                                continue;
                            }else{
                                int i=studentDao.change(s);
                                if(i>0){
                                    System.out.println("修改成功！");
                                }else{
                                    System.out.println("系统异常，信息添加失败！");
                                }
                            }
                        }
                        break;
                    case "exit":
                        System.out.println("bye bye,欢迎再次使用！");
                        System.exit(0);
                    case "help":
                        studentDao.menu();
                        break;
                    default:
                        System.out.println("不合法输入！");

                }
            } catch (Exception e) {
                System.out.println("输入出错！");
                e.printStackTrace();
                continue;
            }
        }
    }
    

}

View Code

package com.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class JDBC {
    private final String DRIVER="com.mysql.jdbc.Driver";
    private final String URL="jdbc:mysql://localhost:3306/test";
    String username = "root" ;   
    String password = "root" ;  
    Connection conn=null;
    
    public Connection getConn(){
        try{ 
            Class.forName(DRIVER);
           conn =DriverManager.getConnection(URL,username,password) ;   
             }catch(SQLException se){   
            System.out.println("数据库连接失败！");   
            se.printStackTrace() ;   
             } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        return conn;   
    } 

}

View Code

1、switch可以使用穿透，就是多个选项同一个效果。

switch(c){
   case 1:
   case 2:
             System.out.println("nihao");
             break;
   default:
             System.out.println("byby");                   
}

2、接收到的数据类型是否对应类型可以不必使用Scanner的hasNextInt（），而使用try、catch异常处理判断类型接受的是否正确，因为错误的类型会抛出异常。

3、在实现多个同级模块的功能后返回初始的选择可以使用while循环镶嵌switch达到，返回的话只需要在需要的位置跳出switch循环就好了。

4、学会使用三目运算符简化代码。