SOS请问第四题如何写？知识点结合在一起就不会写了。

SOS！java习题！请问图中题目要怎么写？知识点都会，结合在一起就不会了。😰
求求帮忙回答！

下面是一个使用缓存实现对文本文件进行读写操作的Java程序示例，其中包括学生类和各种操作。

import java.io.*;
import java.util.HashMap;
import java.util.Map;

class Student implements Serializable {
    private String name;
    private String gender;
    private int age;

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

    public String getName() {
        return name;
    }

    public String getGender() {
        return gender;
    }

    public int getAge() {
        return age;
    }

    @Override
    public String toString() {
        return "Name: " + name + ", Gender: " + gender + ", Age: " + age;
    }
}

class StudentFileCache {
    private Map<Integer, Student> cache;
    private String filePath;

    public StudentFileCache(String filePath) {
        this.filePath = filePath;
        cache = new HashMap<>();
        loadCache();
    }

    public void addStudent(int position, Student student) {
        cache.put(position, student);
        saveCache();
    }

    public Student getStudent(int position) {
        return cache.get(position);
    }

    public void deleteStudent(int position) {
        cache.remove(position);
        saveCache();
    }

    public void updateStudent(int position, Student updatedStudent) {
        cache.put(position, updatedStudent);
        saveCache();
    }

    public void insertStudent(int position, Student student) {
        Map<Integer, Student> updatedCache = new HashMap<>();
        for (Map.Entry<Integer, Student> entry : cache.entrySet()) {
            int key = entry.getKey();
            if (key >= position) {
                updatedCache.put(key + 1, entry.getValue());
            } else {
                updatedCache.put(key, entry.getValue());
            }
        }
        updatedCache.put(position, student);
        cache = updatedCache;
        saveCache();
    }

    private void loadCache() {
        try {
            FileInputStream fileInputStream = new FileInputStream(filePath);
            ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream);
            cache = (HashMap<Integer, Student>) objectInputStream.readObject();
            objectInputStream.close();
            fileInputStream.close();
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    private void saveCache() {
        try {
            FileOutputStream fileOutputStream = new FileOutputStream(filePath);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);
            objectOutputStream.writeObject(cache);
            objectOutputStream.close();
            fileOutputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

public class Main {
    public static void main(String[] args) {
        String filePath = "students_cache.txt";
        StudentFileCache fileCache = new StudentFileCache(filePath);

        // Add students
        Student student1 = new Student("Alice", "Female", 20);
        Student student2 = new Student("Bob", "Male", 21);
        Student student3 = new Student("Charlie", "Male", 19);
        fileCache.addStudent(1, student1);
        fileCache.addStudent(2, student2);
        fileCache.addStudent(3, student3);

        // Get student at position 2
        Student retrievedStudent = fileCache.getStudent(2);
        System.out.println("Retrieved student: " + retrievedStudent);

        // Update student at position 2
        Student updatedStudent = new Student("Bob", "Male", 22);
        fileCache.updateStudent(2, updatedStudent);

        // Delete student at position 1
        fileCache.deleteStudent(1);

        // Insert new student at position 2
        Student newStudent = new Student("Eve", "Female", 18);
        fileCache.insertStudent(2, newStudent);

        // Get all students
        for (int i = 1; i <= fileCache.getStudentCount(); i++) {
            Student student = fileCache.getStudent(i);
            System.out.println("Position " + i + ": " + student);
        }
    }
}

上述代码中，创建了一个Main类，并在main方法中展示了如何使用StudentFileCache类来进行学生信息的读写操作。我们首先创建一个文件缓存对象fileCache，并使用addStudent方法添加了几个学生对象到指定的位置。然后，我们展示了如何使用getStudent方法来获取指定位置的学生信息，并使用updateStudent方法更新指定位置的学生信息。接着，我们使用deleteStudent方法删除指定位置的学生信息，并使用insertStudent方法在指定位置插入新的学生信息。最后，我们展示了如何遍历所有学生信息并打印出来。

请注意，在运行代码之前，请确保目标文件students_cache.txt已存在或有可写权限。

求求帮忙啊啊啊啊！很紧急！！