请用Java写一个学生管理系统，包含学生的学号、名字、性别。班级

和成绩。学生可以添加、删除、修改和查看自己的信息以及所有学生的信息。

以下是一个简单的学生管理系统的示例代码：

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

public class StudentManagementSystem {

private static ArrayList<Student> studentList = new ArrayList<>();

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

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");
System.out.println("4. 查看学生");
System.out.println("5. 退出程序");

int choice = scanner.nextInt();
scanner.nextLine();

switch (choice) {
case 1:
addStudent(scanner);
break;
case 2:
deleteStudent(scanner);
break;
case 3:
updateStudent(scanner);
break;
case 4:
viewStudent(scanner);
break;
case 5:
System.out.println("程序已退出。");
return;
default:
System.out.println("输入无效，请重新输入。");
break;
}
}
}

private static void addStudent(Scanner scanner) {
System.out.print("请输入学生学号：");
String id = scanner.nextLine();

System.out.print("请输入学生名字：");
String name = scanner.nextLine();

System.out.print("请输入学生性别：");
String gender = scanner.nextLine();

System.out.print("请输入学生班级：");
String clazz = scanner.nextLine();

System.out.print("请输入学生成绩：");
int score = scanner.nextInt();
scanner.nextLine();

Student student = new Student(id, name, gender, clazz, score);
studentList.add(student);

System.out.println("学生已添加。");
}

private static void deleteStudent(Scanner scanner) {
System.out.print("请输入要删除的学生学号：");
String id = scanner.nextLine();

Student student = findStudentById(id);
if (student != null) {
studentList.remove(student);
System.out.println("学生已删除。");
} else {
System.out.println("找不到该学生。");
}
}

private static void updateStudent(Scanner scanner) {
System.out.print("请输入要修改的学生学号：");
String id = scanner.nextLine();

Student student = findStudentById(id);
if (student != null) {
System.out.print("请输入学生名字（按回车跳过不修改）：");
String name = scanner.nextLine();
if (!name.equals("")) {
student.setName(name);
}

System.out.print("请输入学生性别（按回车跳过不修改）：");
String gender = scanner.nextLine();
if (!gender.equals("")) {
student.setGender(gender);
}

System.out.print("请输入学生班级（按回车跳过不修改）：");
String clazz = scanner.nextLine();
if (!clazz.equals("")) {
student.setClazz(clazz);
}

System.out.print("请输入学生成绩（按回车跳过不修改）：");
String scoreStr = scanner.nextLine();
if (!scoreStr.equals("")) {
int score = Integer.parseInt(scoreStr);
student.setScore(score);
}

System.out.println("学生已修改。");
} else {
System.out.println("找不到该学生。");
}
}

private static void viewStudent(Scanner scanner) {
System.out.println("请选择要查看的学生：");
System.out.println("1. 查看所有学生");
System.out.println("2. 按学号查看学生");
System.out.println("3. 返回主菜单");

int choice = scanner.nextInt();
scanner.nextLine();

switch (choice) {
case 1:
viewAllStudents();
break;
case 2:
System.out.print("请输入要查看的学生学号：");
String id = scanner.nextLine();

Student student = findStudentById(id);
if (student != null) {
System.out.println(student);
} else {
System.out.println("找不到该学生。");
}
break;
case 3:
return;
default:
System.out.println("输入无效，请重新输入。");
break;
}
}

private static void viewAllStudents() {
for (Student student : studentList) {
System.out.println(student);
}
}

private static Student findStudentById(String id) {
for (Student student : studentList) {
if (student.getId().equals(id)) {
return student;
}
}
return null;
}
}

class Student {

private String id;
private String name;
private String gender;
private String clazz;
private int score;

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

public String getId() {
return id;
}

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

public String getName() {
return name;
}

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

public String getGender() {
return gender;
}

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

public String getClazz() {
return clazz;
}

public void setClazz(String clazz) {
this.clazz = clazz;
}

public int getScore() {
return score;
}

public void setScore(int score) {
this.score = score;
}

@Override
public String toString() {
return "学号：" + id + "，姓名：" + name + "，性别：" + gender + "，班级：" + clazz + "，成绩：" + score;
}
}