实现学生的管理系统代码Java，要求实现 1，学生的注册 2，学生的登入 3，学生的删除 4，学生的查询（包含条件查询，根据学生姓名查询，包括输入第一个姓（如张三的张，输入张这第一个字的时候就出现所有姓张的学生）） 5，学生的信息修改 学生属性 学号（唯一） 用户名 真实名 密码 年龄 性别

以下是一个简单的学生管理系统的 Java 代码：

import java.util.ArrayList;
import java.util.Scanner;

public class StudentManagementSystem {
    public static void main(String[] args) {
        ArrayList<Student> studentList = new ArrayList<>();
        Scanner scanner = new Scanner(System.in);
        boolean exit = false;
        while (!exit) {
            System.out.println("请选择操作：");
            System.out.println("1. 学生注册");
            System.out.println("2. 学生登录");
            System.out.println("3. 学生删除");
            System.out.println("4. 学生查询");
            System.out.println("5. 学生信息修改");
            System.out.println("6. 退出");
            int choice = scanner.nextInt();
            switch (choice) {
                case 1:
                    register(studentList, scanner);
                    break;
                case 2:
                    login(studentList, scanner);
                    break;
                case 3:
                    delete(studentList, scanner);
                    break;
                case 4:
                    search(studentList, scanner);
                    break;
                case 5:
                    modify(studentList, scanner);
                    break;
                case 6:
                    exit = true;
                    break;
                default:
                    System.out.println("无效的操作，请重试！");
            }
        }
    }

    private static void register(ArrayList<Student> studentList, Scanner scanner) {
        System.out.println("请输入学号：");
        String id = scanner.next();
        for (Student student : studentList) {
            if (student.getId().equals(id)) {
                System.out.println("该学号已经被注册！");
                return;
            }
        }
        System.out.println("请输入用户名：");
        String username = scanner.next();
        System.out.println("请输入真实姓名：");
        String realName = scanner.next();
        System.out.println("请输入密码：");
        String password = scanner.next();
        System.out.println("请输入年龄：");
        int age = scanner.nextInt();
        System.out.println("请输入性别（男/女）：");
        String gender = scanner.next();
        Student student = new Student(id, username, realName, password, age, gender);
        studentList.add(student);
        System.out.println("注册成功！");
    }

    private static void login(ArrayList<Student> studentList, Scanner scanner) {
        System.out.println("请输入学号：");
        String id = scanner.next();
        System.out.println("请输入密码：");
        String password = scanner.next();
        for (Student student : studentList) {
            if (student.getId().equals(id)) {
                if (student.getPassword().equals(password)) {
                    System.out.println("登录成功！");
                    return;
                } else {
                    System.out.println("密码错误！");
                    return;
                }
            }
        }
        System.out.println("该学号不存在！");
    }

    private static void delete(ArrayList<Student> studentList, Scanner scanner) {
        System.out.println("请输入学号：");
        String id = scanner.next();
        for (Student student : studentList) {
            if (student.getId().equals(id)) {
                studentList.remove(student);
                System.out.println("删除成功！");
                return;
            }
        }
        System.out.println("该学号不存在！");
    }

    private static void search(ArrayList<Student> studentList, Scanner scanner) {
        System.out.println("请选择查询方式：");
        System.out.println("1. 根据学号查询");
        System.out.println("2. 根据姓名查询");
        int choice = scanner.nextInt();
        switch (choice) {
            case 1:
                System.out.println("请输入学号：");
                String id = scanner.next();
                for (Student student : studentList) {
                    if (student.getId().equals(id)) {
                        System.out.println(student);
                        return;
                    }
                }
                System.out.println("该学号不存在！");
                break;
            case 2:
                System.out.println("请输入姓名首字母：");
                String firstLetter = scanner.next().substring(0, 1);
                boolean found = false;
                for (Student student : studentList) {
                    if (student.getRealName().startsWith(firstLetter)) {
                        System.out.println(student);
                        found = true;
                    }
                }
                if (!found) {
                    System.out.println("没有找到任何学生！");
                }
                break;
            default:
                System.out.println("无效的操作，请重试！");
        }
    }

    private static void modify(ArrayList<Student> studentList, Scanner scanner) {
        System.out.println("请输入学号：");
        String id = scanner.next();
        for (Student student : studentList) {
            if (student.getId().equals(id)) {
                System.out.println("请选择要修改的信息：");
                System.out.println("1. 用户名");
                System.out.println("2. 真实姓名");
                System.out.println("3. 密码");
                System.out.println("4. 年龄");
                System.out.println("5. 性别");
                int choice = scanner.nextInt();
                switch (choice) {
                    case 1:
                        System.out.println("请输入新的用户名：");
                        String username = scanner.next();
                        student.setUsername(username);
                        System.out.println("修改成功！");
                        break;
                    case 2:
                        System.out.println("请输入新的真实姓名：");
                        String realName = scanner.next();
                        student.setRealName(realName);
                        System.out.println("修改成功！");
                        break;
                    case 3:
                        System.out.println("请输入新的密码：");
                        String password = scanner.next();
                        student.setPassword(password);
                        System.out.println("修改成功！");
                        break;
                    case 4:
                        System.out.println("请输入新的年龄：");
                        int age = scanner.nextInt();
                        student.setAge(age);
                        System.out.println("修改成功！");
                        break;
                    case 5:
                        System.out.println("请输入新的性别（男/女）：");
                        String gender = scanner.next();
                        student.setGender(gender);
                        System.out.println("修改成功！");
                        break;
                    default:
                        System.out.println("无效的操作，请重试！");
                }
                return;
            }
        }
        System.out.println("该学号不存在！");
    }
}

class Student {
    private String id;
    private String username;
    private String realName;
    private String password;
    private int age;
    private String gender;

    public Student(String id, String username, String realName, String password, int age, String gender) {
        this.id = id;
        this.username = username;
        this.realName = realName;
        this.password = password;
        this.age = age;
        this.gender = gender;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getRealName() {
        return realName;
    }

    public void setRealName(String realName) {
        this.realName = realName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "学号：" + id + "，用户名：" + username + "，真实姓名：" + realName + "，年龄：" + age + "，性别：" + gender;
    }
}

注意：该代码只是一个简单的示例，实际使用时需要根据具体需求进行修改和完善。