从入门到入土，Java学习day8（集合，学生管理系统实现）_java集合数据库学生管理系统-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_61993735/article/details/145934452

集合

它很重要，因为可以自动扩容，操作起来非常方便

对比

数组长度固定，集合长度可变

数组可以存储基本数据类型和引用数据类型

集合可以存引用数据类型和包装类

当集合需要存基本数据就要存对应的包装类

byte Byte

short Short

char Character

int Integer

long Long

float Float

double Double

boolean Boolean

ArrayList

打印对象不是地址值，而是集合中存储数据内容

在展示的时候会拿[]把所有的数据进行包装

创建

ArrayList<String> list = new ArrayList<String>();

JDK7之后

ArrayList<String> list = new ArrayList<>();

成员方法

boolean add(E e)添加元素，返回值表示是否添加成功

boolean remove(E e)删除指定元素，返回值表示是否删除成功

E remove(int index)删除指定索引的元素，返回被删除元素

E get(int index)获取指定索引的元素

E set(int index,E e)修改指定索引下的元素，返回原来的元素

int size()集合的长度，也就是集合中元素的个数

练习

1.创建集合添加字符串，然后遍历

package jihe;
import java.util.ArrayList;

public class ArrayList1 {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<>();
        list.add("a");
        list.add("b");
        list.add("c");
        list.add("d");
        //遍历
        for (int i = 0; i < list.size(); i++) {
            System.out.println(list.get(i));
        }
    }
}

2.添加数字遍历，代码是一样的，因为JDK5之后基本数据类型和包装类可以相互转化

3.添加学生对象，有姓名和年龄

package jihe;
import java.util.ArrayList;

public class ArrayList2 {
    public static void main(String[] args) {
        ArrayList<Student> list = new ArrayList<>();
        Student s1 = new Student("zhangsan", 23);
        Student s2 = new Student("lisi", 24);
        Student s3 = new Student("wangwu", 25);
        Student s4 = new Student("zhaoliu", 26);
        list.add(s1);
        list.add(s2);
        list.add(s3);
        list.add(s4);
        for (int i = 0; i < list.size(); i++) {
            Student s = list.get(i);
            System.out.println(s.getName() + "," + s.getAge());
        }
    }
}

package jihe;

public class Student {
    private String name;
    private int age;

    public Student() {
    }

    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
}

学生管理系统

看需求，具体需求我就不赘述直接上代码，这个代码可以自己先梳理一下思路，然后分部分来实现，可以模仿跟着写，但最后要独立实现一下，改一改bug提升很大

首先是登录注册界面

package studentsystem;
import java.util.Scanner;
import java.util.ArrayList;

import static studentsystem.Test.getCode;

public class App {
    public static void main(String[] args) {
        ArrayList<User> array = new ArrayList<>();
        System.out.println("欢饮来到学生管理系统");
        System.out.println("请输入你的选择：1登录 2注册 3忘记密码 4退出");
        Scanner sc = new Scanner(System.in);
        int choice = sc.nextInt();
        switch (choice) {
            case 1 -> login(array);
            case 2 -> register(array);
            case 3 -> forgetPassword(array);
            case 4 -> {
                System.out.println("退出学生管理系统");
                System.exit(0);
            }
            default -> System.out.println("输入错误");
        }
    }

    private static void login(ArrayList<User> array) {
        Scanner sc = new Scanner(System.in);
        for (int i = 0; i < 3; i++) {
            System.out.println("请输入你的用户名");
            String username = sc.next();
            boolean flag = contains(array,username);
            if (!flag) {
                System.out.println("用户名不存在，请注册再登录");
                return;
            }
            System.out.println("请输入你的密码");
            String password = sc.next();
            while (true) {
                System.out.println("请输入验证码");
                String code = getCode();
                System.out.println(code);
                String code1 = sc.next();
                if (code.equals(code1)) {
                    System.out.println("验证码正确");
                    break;
                }else {
                    System.out.println("验证码错误");
                }
            }
            boolean flag1 = checkUsernameAndPassword(array,username,password);
            if (flag1) {
                System.out.println("登录成功");
                StudentSystem ss = new StudentSystem();
                ss.startStudentSystem();
                break;
            }else {
                System.out.println("用户名或密码错误");
                if (i == 2) {
                    System.out.println("你已经输入三次，系统退出");
                    return;
                }else {
                    System.out.println("你还有" + (2 - i) + "次机会");
                }
            }
        }
    }



    private static boolean checkUsernameAndPassword(ArrayList<User> array, String username, String password) {
        for (User u : array) {
            if (u.getUsername().equals(username) && u.getPassword().equals(password)) {
                return true;
            }
        }
        return false;
    }

    private static void forgetPassword(ArrayList<User> array) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入你的用户名");
        String username = sc.next();
        boolean flag = contains(array,username);
        if (!flag) {
            System.out.println("用户名不存在，请注册再登录");
            return;
        }
        System.out.println("请输入你的身份证号");
        String personalId = sc.next();

        System.out.println("请输入你的手机号");
        String phoneNumber = sc.next();
        int index = findIndex(array,username);
        User u = array.get(index);
        if (!u.getPersonalId().equals(personalId) && u.getPhoneNumber().equals(phoneNumber)) {
            System.out.println("身份证号或手机号错误");
            return;
        }
        String newPassword;
        while (true) {
            System.out.println("请输入你的新密码");
            newPassword = sc.next();
            System.out.println("请再次输入你的新密码");
            String newPassword1 = sc.next();
            if (!newPassword.equals(newPassword1)) {
                System.out.println("两次密码不一致，请重新输入");
            }else {
                System.out.println("密码输入一致");
                break;
            }
        }
        u.setPassword(newPassword);
        System.out.println("密码修改成功");
    }

    private static int findIndex(ArrayList<User> array, String username) {
        for (int i = 0; i < array.size(); i++) {
            User u = array.get(i);
            if (u.getUsername().equals(username)) {
                return i;
            }
        }
        return -1;
    }

    private static void register(ArrayList<User> array) {
        Scanner sc = new Scanner(System.in);
        String username;
        while (true) {
            username = sc.next();
            boolean flag = checkUsername(username);
            if (!flag) {
                System.out.println("格式不满足，重新输入");
                continue;
            }
            boolean flag1 = contains(array, username);
            if (flag1) {
                System.out.println("用户名已存在，请重新输入");
            }else {
                break;
            }
        }
        String password;
        while (true) {
            System.out.println("请输入你的密码");
            password = sc.next();
            System.out.println("请再次输入密码");
            String password1 = sc.next();
            if (!password.equals(password1)) {
                System.out.println("两次密码不一致，请重新输入");
            }else {
                break;
            }
        }
        String personalId;
        while (true) {
            System.out.println("请输入你的身份证号");
            personalId = sc.next();
            boolean flag2 = checkPersonalId(personalId);
            if (flag2) {
                System.out.println("身份证号格式正确");
                break;
            }else {
                System.out.println("身份证号格式不正确");
            }
        }
        String phoneNumber;
        while (true) {
            System.out.println("请输入你的手机号");
            phoneNumber = sc.next();
            boolean flag = checkPhoneNumber(phoneNumber);
            if (flag) {
                System.out.println("手机号格式正确");
                break;
            }else {
                System.out.println("手机号格式不正确");
            }
        }
        User u = new User(username,password,personalId,phoneNumber);
        array.add(u);
        System.out.println("注册成功");
        printList(array);
        //跳转到登录选项
        login(array);

    }

    private static void printList(ArrayList<User> array) {
        for (User u : array) {
            System.out.println(u.getUsername() + "," + u.getPassword() + "," + u.getPersonalId() + "," + u.getPhoneNumber());
        }
    }

    private static boolean checkPhoneNumber(String phoneNumber) {
        if (phoneNumber.length()!= 11) {
            System.out.println("手机号长度必须为11位");
            return false;
        }
        if (phoneNumber.startsWith("0")){
            System.out.println("手机号不能以0开头");
            return false;
        }
        for (int i = 0; i < phoneNumber.length(); i++) {
            char c = phoneNumber.charAt(i);
            if (!(c >= '0' && c <= '9')) {
                System.out.println("手机号必须由数字组成");
                return false;
            }
        }
        return true;
    }

    private static boolean checkPersonalId(String personalId) {
        if (personalId.length() != 18) {
            System.out.println("身份证号长度必须为18位");
            return false;
        }
        if (personalId.startsWith("0")){
            System.out.println("身份证号不能以0开头");
            return false;
        }
        for (int i = 0; i < personalId.length() - 1; i++) {
            char c = personalId.charAt(i);
            if (!(c >= '0' && c <= '9')) {
                System.out.println("身份证号必须由数字组成");
                return false;
            }
        }
        char endChar = personalId.charAt(personalId.length() - 1);
        if (!(endChar >= '0' && endChar <= '9' || endChar == 'x' || endChar == 'X')) {
            System.out.println("身份证号最后一位必须是数字或x或X");
            return false;
        }
        return true;
    }

    private static boolean contains(ArrayList<User> array, String username) {
        for (User u : array) {
            if (u.getUsername().equals(username)) {
                return true;
            }
        }
        return false;
    }
    private static boolean checkUsername(String username){
        int length = username.length();
        if (length < 3 || length > 15) {
            System.out.println("用户名长度必须在3-15之间");
            return false;
        }
        for (int i = 0; i < username.length(); i++) {
            char c = username.charAt(i);
            if (!(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9')) {
                System.out.println("用户名只能由字母和数字组成");
                return false;
            }
        }
        int count = 0;
        for (int i = 0; i < username.length(); i++) {
            char c = username.charAt(i);
            if ((c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' )) {
                count++;
                break;
            }
        }
        return count > 0;
    }


}

登录成功之后进入学生系统管理界面

package studentsystem;
import java.util.Scanner;
import java.util.ArrayList;

public class StudentSystem {
    public static void startStudentSystem() {
        ArrayList<Student> array = new ArrayList<>();
        loop:while (true) {
            System.out.println("---------学生管理系统-----------");
            System.out.println("1.添加学生");
            System.out.println("2.删除学生");
            System.out.println("3.修改学生");
            System.out.println("4.查询学生");
            System.out.println("5.退出学生管理系统");
            System.out.println("请输入你的选择：");
            Scanner sc = new Scanner(System.in);
            String choice = sc.next();
            switch (choice) {
                case "1" -> addStudent(array);
                case "2" -> deleteStudent(array);
                case "3" -> updateStudent(array);
                case "4" -> queryStudent(array);
                case "5" -> {
                    System.out.println("退出学生管理系统");
                    break loop;
                    //System.exit(0);
                }
                default -> System.out.println("输入错误");
            }
        }
    }
    //添加学生
    public static void addStudent(ArrayList<Student> array) {
        Scanner sc = new Scanner(System.in);
        Student s = new Student();
        while (true) {
            System.out.println("请输入学生id");
            String id = sc.next();
            boolean flag = contains(array, id);
            if (flag) {
                System.out.println("id已存在，请重新输入");
            }else {
                s.setId(id);
                break;
            }
        }
        System.out.println("请输入学生姓名");
        String name = sc.next();
        s.setName(name);
        System.out.println("请输入学生年龄");
        int age = sc.nextInt();
        s.setAge(age);
        System.out.println("请输入学生居住地");
        String address = sc.next();
        s.setAddress(address);
        array.add(s);
        System.out.println("添加学生成功");

    }
    //删除学生
    public static void deleteStudent(ArrayList<Student> array) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入要删除的学生id");
        String id = sc.next();
        int index = getIndex(array, id);
        if (index == -1) {
            System.out.println("id不存在，请重新输入");
        }else {
            array.remove(index);
            System.out.println("删除学生成功");
        }
    }
    //修改学生
    public static void updateStudent(ArrayList<Student> array) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入要修改的学生id");
        String id = sc.next();
        int index = getIndex(array, id);
        if (index == -1) {
            System.out.println("id不存在，请重新输入");
            return;
        }
        Student s = array.get(index);
        System.out.println("请输入学生姓名");
        String name = sc.next();
        s.setName(name);
        System.out.println("请输入学生年龄");
        int age = sc.nextInt();
        s.setAge(age);
        System.out.println("请输入学生居住地");
        String address = sc.next();
        s.setAddress(address);
        array.set(index, s);
        System.out.println("修改学生成功");
    }
    //查询学生
    public static void queryStudent(ArrayList<Student> array) {
        if (array.isEmpty()) {
            System.out.println("无信息，请先添加信息再查询");
            return;
        }
        System.out.println("学号\t\t姓名\t年龄\t居住地");
        for (Student s : array) {
            System.out.println(s.getId() + "\t" + s.getName() + "\t" + s.getAge() + "\t" + s.getAddress());
        }
    }
    public static boolean contains(ArrayList<Student> array, String id) {
       /* for (int i = 0; i < array.size(); i++) {
            Student s = array.get(i);
            if (s.getId().equals(id)) {
                return true;
            }
        }
        return false;*/
        return getIndex(array, id) >= 0;
    }
    public static int getIndex(ArrayList<Student> array, String id) {
        for (int i = 0; i < array.size(); i++) {
            Student s = array.get(i);
            if (s.getId().equals(id)) {
                return i;
            }
        }
        return -1;
    }
}

然后是三个支持的模块，验证码获取方法

package studentsystem;

import java.util.ArrayList;
import java.util.Random;

public class Test {
    public static void main(String[] args) {
        System.out.println(getCode());
    }
    static String getCode() {
        ArrayList<Character> list = new ArrayList<>();
        for (int i = 0; i < 26; i++) {
            list.add((char) ('A' + i));
            list.add((char) ('a' + i));
        }
        StringBuilder sb = new StringBuilder();
        Random r = new Random();
        for (int i = 0; i < 4; i++) {
            int index = r.nextInt(list.size());
            char c = list.get(index);
            sb.append(c);
        }
        int number = r.nextInt(10);
        sb.append(number);
        char[] arr = sb.toString().toCharArray();
        int randomIndex = r.nextInt(sb.length());
        char temp = arr[randomIndex];
        arr[randomIndex] = arr[arr.length - 1];
        arr[arr.length - 1] = temp;
        String result = new String(arr);
        return result;
    }
}

用户和学生标准类

package studentsystem;

public class Student {
    private String name;
    private String id;
    private int age;
    private String address;

    public Student() {
    }

    public Student(String name, String id, int age, String address) {
        this.name = name;
        this.id = id;
        this.age = age;
        this.address = address;
    }

    /**
     * 获取
     * @return name
     */
    public String getName() {
        return name;
    }

    /**
     * 设置
     * @param name
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * 获取
     * @return id
     */
    public String getId() {
        return id;
    }

    /**
     * 设置
     * @param id
     */
    public void setId(String id) {
        this.id = id;
    }

    /**
     * 获取
     * @return age
     */
    public int getAge() {
        return age;
    }

    /**
     * 设置
     * @param age
     */
    public void setAge(int age) {
        this.age = age;
    }

    /**
     * 获取
     * @return address
     */
    public String getAddress() {
        return address;
    }

    /**
     * 设置
     * @param address
     */
    public void setAddress(String address) {
        this.address = address;
    }


}

package studentsystem;

public class User {
    private String username;
    private String password;
    private String personalId;
    private String phoneNumber;

    public User() {
    }

    public User(String username, String password, String personalId, String phoneNumber) {
        this.username = username;
        this.password = password;
        this.personalId = personalId;
        this.phoneNumber = phoneNumber;
    }

    /**
     * 获取
     * @return username
     */
    public String getUsername() {
        return username;
    }

    /**
     * 设置
     * @param username
     */
    public void setUsername(String username) {
        this.username = username;
    }

    /**
     * 获取
     * @return password
     */
    public String getPassword() {
        return password;
    }

    /**
     * 设置
     * @param password
     */
    public void setPassword(String password) {
        this.password = password;
    }

    /**
     * 获取
     * @return personalId
     */
    public String getPersonalId() {
        return personalId;
    }

    /**
     * 设置
     * @param personalId
     */
    public void setPersonalId(String personalId) {
        this.personalId = personalId;
    }

    /**
     * 获取
     * @return phoneNumber
     */
    public String getPhoneNumber() {
        return phoneNumber;
    }

    /**
     * 设置
     * @param phoneNumber
     */
    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }

}