用java写一个学生管理系统

好的，下面是一个简单的学生管理系统的Java代码，包括添加学生、删除学生、修改学生信息和查找学生信息等功能：

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

public class StudentManagementSystem {

    private ArrayList<Student> students;

    public StudentManagementSystem() {
        students = new ArrayList<Student>();
    }

    public void addStudent() {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入学生姓名：");
        String name = scanner.next();

        System.out.println("请输入学生学号：");
        String id = scanner.next();

        System.out.println("请输入学生年龄：");
        int age = scanner.nextInt();

        System.out.println("请输入学生性别（男/女）：");
        String gender = scanner.next();

        Student student = new Student(name, id, age, gender);
        students.add(student);

        System.out.println("添加成功！");
    }

    public void deleteStudent() {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入要删除的学生学号：");
        String id = scanner.next();

        for (int i = 0; i < students.size(); i++) {
            Student student = students.get(i);
            if (student.getId().equals(id)) {
                students.remove(i);
                System.out.println("删除成功！");
                return;
            }
        }

        System.out.println("没找到该学生！");
    }

    public void updateStudent() {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入要修改的学生学号：");
        String id = scanner.next();

        for (int i = 0; i < students.size(); i++) {
            Student student = students.get(i);
            if (student.getId().equals(id)) {
                System.out.println("请输入学生姓名（原姓名：" + student.getName() + "）：");
                String name = scanner.next();

                System.out.println("请输入学生年龄（原年龄：" + student.getAge() + "）：");
                int age = scanner.nextInt();

                System.out.println("请输入学生性别（原性别：" + student.getGender() + "）：");
                String gender = scanner.next();

                student.setName(name);
                student.setAge(age);
                student.setGender(gender);

                System.out.println("修改成功！");
                return;
            }
        }

        System.out.println("没找到该学生！");
    }

    public void queryStudent() {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入要查询的学生学号：");
        String id = scanner.next();

        for (int i = 0; i < students.size(); i++) {
            Student student = students.get(i);
            if (student.getId().equals(id)) {
                System.out.println("学生姓名：" + student.getName());
                System.out.println("学生学号：" + student.getId());
                System.out.println("学生年龄：" + student.getAge());
                System.out.println("学生性别：" + student.getGender());
                return;
            }
        }

        System.out.println("没找到该学生！");
    }

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

        StudentManagementSystem system = new StudentManagementSystem();

        while (true) {
            System.out.println("请选择操作：");
            System.out.println("1. 添加学生");
            System.out.println("2. 删除学生");
            System.out.println("3. 修改学生信息");
            System.out.println("4. 查找学生信息");
            System.out.println("5. 退出");

            int choice = scanner.nextInt();

            switch (choice) {
            case 1:
                system.addStudent();
                break;
            case 2:
                system.deleteStudent();
                break;
            case 3:
                system.updateStudent();
                break;
            case 4:
                system.queryStudent();
                break;
            case 5:
                System.exit(0);
            }
        }
    }

}

class Student {

    private String name;
    private String id;
    private int age;
    private String gender;

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getId() {
        return id;
    }

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

    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;
    }

}

以上代码实现了一个简单的学生管理系统，可以添加、删除、修改和查询学生信息。