Student Management System

import java.util.*;

public class StudentManagementSystem {

    static class Student {
        String name;
        int age;
        List<Integer> grades;
        int attendance;

        public Student(String name, int age) {
            this.name = name;
            this.age = age;
            this.grades = new ArrayList<>();
            this.attendance = 0;
        }

        public void addGrade(int grade) {
            grades.add(grade);
        }

        public void updateAttendance(int daysAttended) {
            this.attendance = daysAttended;
        }

        public double calculateAverageGrade() {
            if (grades.isEmpty()) return 0.0;
            int total = 0;
            for (int grade : grades) {
                total += grade;
            }
            return total / (double) grades.size();
        }

        public String getPerformance() {
            double average = calculateAverageGrade();
            if (average >= 90) return "Excellent";
            if (average >= 75) return "Good";
            if (average >= 50) return "Average";
            return "Needs Improvement";
        }

        @Override
        public String toString() {
            return "Student{name='" + name + "', age=" + age + ", grades=" + grades + ", attendance=" + attendance + "}";
        }
    }

    private Map<Integer, Student> studentMap; // Keyed by student ID

    public StudentManagementSystem() {
        studentMap = new HashMap<>();
    }

    public void addStudent(int studentId, String name, int age) {
        if (studentMap.containsKey(studentId)) {
            System.out.println("Student ID already exists.");
        } else {
            studentMap.put(studentId, new Student(name, age));
        }
    }

    public void addGradeToStudent(int studentId, int grade) {
        Student student = studentMap.get(studentId);
        if (student != null) {
            student.addGrade(grade);
        } else {
            System.out.println("Student not found.");
        }
    }

    public void updateStudentAttendance(int studentId, int daysAttended) {
        Student student = studentMap.get(studentId);
        if (student != null) {
            student.updateAttendance(daysAttended);
        } else {
            System.out.println("Student not found.");
        }
    }

    public void printStudentDetails(int studentId) {
        Student student = studentMap.get(studentId);
        if (student != null) {
            System.out.println(student);
            System.out.println("Average Grade: " + student.calculateAverageGrade());
            System.out.println("Performance: " + student.getPerformance());
        } else {
            System.out.println("Student not found.");
        }
    }

    public void printClassReport() {
        for (Map.Entry<Integer, Student> entry : studentMap.entrySet()) {
            Student student = entry.getValue();
            System.out.println("ID: " + entry.getKey() + " | Name: " + student.name + " | Average Grade: " + student.calculateAverageGrade() + " | Attendance: " + student.attendance + " | Performance: " + student.getPerformance());
        }
    }

    public static void main(String[] args) {
        StudentManagementSystem sms = new StudentManagementSystem();

        // Adding students
        sms.addStudent(1, "John Doe", 20);
        sms.addStudent(2, "Jane Smith", 21);

        // Adding grades
        sms.addGradeToStudent(1, 85);
        sms.addGradeToStudent(1, 90);
        sms.addGradeToStudent(2, 78);
        sms.addGradeToStudent(2, 82);

        // Updating attendance
        sms.updateStudentAttendance(1, 20);
        sms.updateStudentAttendance(2, 18);

        // Printing student details
        sms.printStudentDetails(1);
        sms.printStudentDetails(2);

        // Printing class report
        sms.printClassReport();
    }
}