用java中的io流文件设计一个简单的学生成绩系统，该学生管理系统再次登录时，之前保存的学生信息可以查出来。具有以下功能：添加一个学生；查找一个学生；根据编号更新学生的基本信息（基本信息为姓名与学号）；根据编号删除学生；根据编号输入学生的各门成绩（语文、数学、外语，成绩为int类型）；退出系统。

好的，下面是一个简单的学生成绩管理系统的设计，具体实现如下：

1. 创建一个名为`Student`的类，用于封装学生信息，包括姓名、学号和成绩。

public class Student {
    private String name;
    private int id;
    private int chineseScore;
    private int mathScore;
    private int englishScore;

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

    public String getName() {
        return name;
    }

    public int getId() {
        return id;
    }

    public int getChineseScore() {
        return chineseScore;
    }

    public void setChineseScore(int chineseScore) {
        this.chineseScore = chineseScore;
    }

    public int getMathScore() {
        return mathScore;
    }

    public void setMathScore(int mathScore) {
        this.mathScore = mathScore;
    }

    public int getEnglishScore() {
        return englishScore;
    }

    public void setEnglishScore(int englishScore) {
        this.englishScore = englishScore;
    }
}

2. 创建一个名为`StudentManager`的类，用于管理学生信息。可以通过该类实现添加、查找、更新和删除学生信息的功能。在该类中，我们使用文件流将学生信息保存到文件中，以便再次启动程序时可以读取之前保存的学生信息。

import java.io.*;
import java.util.ArrayList;

public class StudentManager {
    private ArrayList<Student> students;
    private File file;

    public StudentManager(String fileName) {
        students = new ArrayList<>();
        file = new File(fileName);
        if (file.exists()) {
            loadFromFile();
        } else {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public void add(Student student) {
        students.add(student);
        saveToFile();
    }

    public Student find(int id) {
        for (Student student : students) {
            if (student.getId() == id) {
                return student;
            }
        }
        return null;
    }

    public void update(int id, String name, int newId) {
        Student student = find(id);
        if (student != null) {
            student.setName(name);
            student.setId(newId);
            saveToFile();
        }
    }

    public void delete(int id) {
        Student student = find(id);
        if (student != null) {
            students.remove(student);
            saveToFile();
        }
    }

    public void setScore(int id, int chineseScore, int mathScore, int englishScore) {
        Student student = find(id);
        if (student != null) {
            student.setChineseScore(chineseScore);
            student.setMathScore(mathScore);
            student.setEnglishScore(englishScore);
            saveToFile();
        }
    }

    private void saveToFile() {
        try {
            FileOutputStream fos = new FileOutputStream(file);
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(students);
            oos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void loadFromFile() {
        try {
            FileInputStream fis = new FileInputStream(file);
            ObjectInputStream ois = new ObjectInputStream(fis);
            students = (ArrayList<Student>) ois.readObject();
            ois.close();
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

3. 创建一个名为`Main`的类，用于演示学生成绩管理系统的功能。在主函数中，我们创建一个`StudentManager`对象，并通过控制台输入来实现添加、查找、更新和删除学生信息的功能。

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        StudentManager manager = new StudentManager("students.dat");

        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("请选择功能：");
            System.out.println("1. 添加学生");
            System.out.println("2. 查找学生");
            System.out.println("3. 更新学生信息");
            System.out.println("4. 删除学生");
            System.out.println("5. 输入学生成绩");
            System.out.println("6. 退出系统");

            int choice = scanner.nextInt();
            switch (choice) {
                case 1:
                    System.out.print("请输入学生姓名：");
                    String name = scanner.next();
                    System.out.print("请输入学号：");
                    int id = scanner.nextInt();
                    manager.add(new Student(name, id));
                    System.out.println("添加成功！");
                    break;
                case 2:
                    System.out.print("请输入学号：");
                    id = scanner.nextInt();
                    Student student = manager.find(id);
                    if (student != null) {
                        System.out.println("姓名：" + student.getName());
                        System.out.println("学号：" + student.getId());
                        System.out.println("语文成绩：" + student.getChineseScore());
                        System.out.println("数学成绩：" + student.getMathScore());
                        System.out.println("英语成绩：" + student.getEnglishScore());
                    } else {
                        System.out.println("学号为" + id + "的学生不存在！");
                    }
                    break;
                case 3:
                    System.out.print("请输入学号：");
                    id = scanner.nextInt();
                    System.out.print("请输入新的姓名：");
                    name = scanner.next();
                    System.out.print("请输入新的学号：");
                    int newId = scanner.nextInt();
                    manager.update(id, name, newId);
                    System.out.println("更新成功！");
                    break;
                case 4:
                    System.out.print("请输入学号：");
                    id = scanner.nextInt();
                    manager.delete(id);
                    System.out.println("删除成功！");
                    break;
                case 5:
                    System.out.print("请输入学号：");
                    id = scanner.nextInt();
                    System.out.print("请输入语文成绩：");
                    int chineseScore = scanner.nextInt();
                    System.out.print("请输入数学成绩：");
                    int mathScore = scanner.nextInt();
                    System.out.print("请输入英语成绩：");
                    int englishScore = scanner.nextInt();
                    manager.setScore(id, chineseScore, mathScore, englishScore);
                    System.out.println("输入成功！");
                    break;
                case 6:
                    System.exit(0);
                    break;
                default:
                    System.out.println("无效的选择！");
            }
        }
    }
}

以上就是一个简单的学生成绩管理系统的实现，可以通过文件流来保存和读取学生信息，从而实现再次启动程序时可以查出之前保存的学生信息的功能。