المشروع الشامل: نظام إدارة الطلاب

package school.model; public interface Reportable {    String report();}

package school.model; public abstract class Person {    private int id;    private String name;     public Person(int id, String name) {        this.id = id;        this.name = name;    }     public int getId() {        return id;    }     public String getName() {        return name;    }     public abstract void printInfo();}

package school.model; public class Student extends Person implements Reportable {    public static final double PASS_MARK = 60;    private static int count = 0;    private double mark;     public Student(int id, String name, double mark) {        super(id, name);        setMark(mark);        count++;    }     public double getMark() {        return mark;    }     public void setMark(double mark) {        if (mark < 0 || mark > 100)            throw new IllegalArgumentException("الدرجة يجب أن تكون بين 0 و 100");        this.mark = mark;    }     public String getResult() {        if (mark >= PASS_MARK)            return "Pass";        else            return "Fail";    }     public static int getCount() {        return count;    }     @Override    public void printInfo() {        System.out.println("Student: " + getId() + " | " + getName()                + " | " + mark + " | " + getResult());    }     @Override    public String report() {        return getId() + "," + getName() + "," + mark + "," + getResult();    }}

package school.model; public class Teacher extends Person {    private String subject;     public Teacher(int id, String name, String subject) {        super(id, name);        this.subject = subject;    }     @Override    public void printInfo() {        System.out.println("Teacher: " + getId() + " | " + getName() + " | " + subject);    }}

package school.app; import java.io.File;import java.io.FileNotFoundException;import java.io.FileWriter;import java.io.IOException;import java.util.ArrayList;import java.util.Scanner;import school.model.Student; public class School {    private ArrayList<Student> students = new ArrayList<>();     public void addStudent(Student s) {        students.add(s);    }     public double average() {        double sum = 0;        for (Student s : students) {            sum = sum + s.getMark();        }        return sum / students.size();    }     public Student topStudent() {        Student top = students.get(0);        for (Student s : students) {            if (s.getMark() > top.getMark())                top = s;        }        return top;    }     public void saveToFile(String fileName) throws IOException {        FileWriter writer = new FileWriter(fileName);        for (Student s : students) {            writer.write(s.report() + "\n");        }        writer.close();    }     public void printFile(String fileName) throws FileNotFoundException {        Scanner reader = new Scanner(new File(fileName));        while (reader.hasNextLine()) {            System.out.println(reader.nextLine());        }        reader.close();    }}

package school.app; import java.io.IOException;import java.util.ArrayList;import school.model.Person;import school.model.Student;import school.model.Teacher; public class Main {    public static void main(String[] args) {        School school = new School();         // 1) إضافة الطلاب        school.addStudent(new Student(4321, "Mohammed", 80));        school.addStudent(new Student(4344, "Turki", 50));        school.addStudent(new Student(4355, "Fahad", 92));         // 2) معالجة درجة غير صحيحة        try {            school.addStudent(new Student(4366, "Ali", 120));        } catch (IllegalArgumentException e) {            System.out.println("خطأ: " + e.getMessage());        }         // 3) تعدد الأشكال: قائمة من نوع الأب Person        ArrayList<Person> people = new ArrayList<>();        people.add(new Teacher(1, "Saud", "Java"));        people.add(school.topStudent());        for (Person p : people) {            p.printInfo();        }         // 4) الإحصاءات        System.out.println("Students: " + Student.getCount());        System.out.println("Average: " + school.average());         // 5) الحفظ في ملف ثم القراءة منه        try {            school.saveToFile("students.txt");            System.out.println("--- students.txt ---");            school.printFile("students.txt");        } catch (IOException e) {            System.out.println("خطأ في الملف: " + e.getMessage());        }    }}