Project.java

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

class Student {
    int id;
    String name;
    int totalClasses;
    int attendedClasses;
    int marks;

    Student(int id, String name, int totalClasses, int attendedClasses, int marks) {
        this.id = id;
        this.name = name;
        this.totalClasses = totalClasses;
        this.attendedClasses = attendedClasses;
        this.marks = marks;
    }

    double getAttendancePercentage() {
        if (totalClasses == 0) return 0;
        return (attendedClasses * 100.0) / totalClasses;
    }
}

public class Project {

    static void displayStudent(Student s) {
        double percentage = s.getAttendancePercentage();

        System.out.println("\nID: " + s.id);
        System.out.println("Name: " + s.name);
        System.out.println("Marks: " + s.marks);
        System.out.printf("Attendance: %.2f%%\n", percentage);

        if (percentage < 75)
            System.out.println("Status: Warning (Low Attendance)");
        else
            System.out.println("Status: OK");
    }

   
    static void addStudent(ArrayList<Student> students, BufferedReader br) throws IOException {
        System.out.print("Enter ID: ");
        int id = Integer.parseInt(br.readLine());

        for (int i = 0; i < students.size(); i++) {
            if (students.get(i).id == id) {
                System.out.println("ID already exists!");
                return;
            }
        }

        System.out.print("Enter Name: ");
        String name = br.readLine();

        System.out.print("Total Classes: ");
        int total = Integer.parseInt(br.readLine());

        System.out.print("Attended Classes: ");
        int attended = Integer.parseInt(br.readLine());

        System.out.print("Marks: ");
        int marks = Integer.parseInt(br.readLine());

        students.add(new Student(id, name, total, attended, marks));
        System.out.println("Student added.");
    }

   
    static void deleteStudent(ArrayList<Student> students, int id) {
        for (int i = 0; i < students.size(); i++) {
            if (students.get(i).id == id) {
                students.remove(i);
                System.out.println("Student deleted.");
                return;
            }
        }
        System.out.println("Student not found.");
    }

   
    static void updateStudent(ArrayList<Student> students, BufferedReader br, int id) throws IOException {
        for (int i = 0; i < students.size(); i++) {
            if (students.get(i).id == id) {

                Student s = students.get(i);

                System.out.print("Enter new name: ");
                s.name = br.readLine();

                System.out.print("Enter new total classes: ");
                s.totalClasses = Integer.parseInt(br.readLine());

                System.out.print("Enter new attended classes: ");
                s.attendedClasses = Integer.parseInt(br.readLine());

                System.out.print("Enter new marks: ");
                s.marks = Integer.parseInt(br.readLine());

                System.out.println("Student updated.");
                return;
            }
        }
        System.out.println("Student not found.");
    }

   
    static void viewAll(ArrayList<Student> students) {
        if (students.isEmpty()) {
            System.out.println("No data.");
            return;
        }

        for (int i = 0; i < students.size(); i++) {
            displayStudent(students.get(i));
        }
    }

  
    static void showStars(ArrayList<Student> students) {
        for (int i = 0; i < students.size(); i++) {
            Student s = students.get(i);

            System.out.print(s.name + " : ");
            int bars = s.marks / 10;

            for (int j = 0; j < bars; j++) {
                System.out.print("#");
            }

            System.out.println(" (" + s.marks + ")");
        }
    }

    static void saveToFile(ArrayList<Student> students) throws IOException {
        BufferedWriter bw = new BufferedWriter(new FileWriter("students.csv"));

        for (int i = 0; i < students.size(); i++) {
            Student s = students.get(i);
            bw.write(s.id + "," + s.name + "," + s.totalClasses + "," + s.attendedClasses + "," + s.marks);
            bw.newLine();
        }

        bw.close();
    }

   
    static void loadFromFile(ArrayList<Student> students) throws IOException {
        File file = new File("students.csv");
        if (!file.exists()) return;

        BufferedReader br = new BufferedReader(new FileReader(file));
        String line;

        while ((line = br.readLine()) != null) {
            String[] d = line.split(",");

            students.add(new Student(
                    Integer.parseInt(d[0]),
                    d[1],
                    Integer.parseInt(d[2]),
                    Integer.parseInt(d[3]),
                    Integer.parseInt(d[4])
            ));
        }
        br.close();
    }

  
    static void viewCSV() throws IOException {
        File file = new File("students.csv");

        if (!file.exists()) {
            System.out.println("File not found.");
            return;
        }

        BufferedReader br = new BufferedReader(new FileReader(file));
        String line;

        System.out.println("\n--- CSV FILE DATA ---");

        while ((line = br.readLine()) != null) {
            System.out.println(line);
        }

        br.close();
    }

    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        ArrayList<Student> students = new ArrayList<>();

        loadFromFile(students);

        while (true) {
            System.out.println("\n===== MENU =====");
            System.out.println("1. Add Student");
            System.out.println("2. View All");
            System.out.println("3. Search Student");
            System.out.println("4. Show Stars");
            System.out.println("5. Delete Student");
            System.out.println("6. Update Student");
            System.out.println("7. View CSV File");
            System.out.println("8. Exit");

            System.out.print("Enter choice: ");
            int ch = Integer.parseInt(br.readLine());

            switch (ch) {

                case 1:
                    addStudent(students, br);
                    break;

                case 2:
                    viewAll(students);
                    break;

                case 3:
                    System.out.print("Enter ID: ");
                    int id = Integer.parseInt(br.readLine());
                    for (int i = 0; i < students.size(); i++) {
                        if (students.get(i).id == id) {
                            displayStudent(students.get(i));
                            break;
                        }
                    }
                    break;

                case 4:
                    showStars(students);
                    break;

                case 5:
                    System.out.print("Enter ID to delete: ");
                    deleteStudent(students, Integer.parseInt(br.readLine()));
                    break;

                case 6:
                    System.out.print("Enter ID to update: ");
                    updateStudent(students, br, Integer.parseInt(br.readLine()));
                    break;

                case 7:
                    viewCSV();
                    break;

                case 8:
                    saveToFile(students);
                    System.out.println("Saved & Exiting...");
                    System.exit(0);

                default:
                    System.out.println("Invalid choice.");
            }
        }
    }
}