student_management.java

// Student Management System using file handling

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


class Student {
    int id;
    String name;
    int age;
    String grade;

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

    public String toFileString() {
        return id + "," + name + "," + age + "," + grade;
    }

    public void display() {
        System.out.println("ID: " + id + ", Name: " + name + ", Age: " + age + ", Grade: " + grade);
    }
}


public class Main {

    static final String FILE_NAME = "students.txt";
    static ArrayList<Student> studentList = new ArrayList<>();
    static Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        loadFile();

        int choice;
        do {
            System.out.println("\n--- Student Management System ---");
            System.out.println("1. Add Student");
            System.out.println("2. View Students");
            System.out.println("3. Update Student");
            System.out.println("4. Delete Student");
            System.out.println("5. Search Student");
            System.out.println("6. Exit");
            System.out.print("Enter choice: ");
            choice = sc.nextInt();
            sc.nextLine(); 

            switch (choice) {
                case 1 : addStudent(); break;
                case 2 : viewStudents(); break;
                case 3 : updateStudent(); break;
                case 4 : deleteStudent(); break;
                case 5 : searchStudent(); break;
                case 6 : {
                    saveToFile();
                    System.out.println("Exiting... Data saved.");
                } break;
                default : System.out.println("Invalid choice!");
            }
        } while (choice != 6);
    }

  
static void loadFile() {
    try (BufferedReader br = new BufferedReader(new FileReader(FILE_NAME))) {
        String line;

        while ((line = br.readLine()) != null) {

            String[] data = line.split(",");

            if (data.length != 4) {
                System.out.println("Invalid record skipped: " + line);
                continue;
            }

            try {
                Student s = new Student(
                    Integer.parseInt(data[0]),
                    data[1],
                    Integer.parseInt(data[2]),
                    data[3]
                );

                studentList.add(s);

            } catch (NumberFormatException e) {
                System.out.println("Invalid number format. Record skipped: " + line);
            }
        }

    } catch (FileNotFoundException e) {
        System.out.println("No existing file found. Starting fresh.");

    } catch (IOException e) {
        System.out.println("Error reading file.");
    }
}


    // Save
    static void saveToFile() {
        try (BufferedWriter bw = new BufferedWriter(new FileWriter(FILE_NAME))) {
            for (Student s : studentList) {
                bw.write(s.toFileString());
                bw.newLine();
            }
        } catch (IOException e) {
            System.out.println("Error saving file.");
        }
    }

    // Add
    static void addStudent() {
        System.out.print("Enter ID: ");
        int id = sc.nextInt();
        sc.nextLine();

       
        for (Student s : studentList) {
            if (s.id == id) {
                System.out.println("Student with this ID already exists!");
                return;
            }
        }

        System.out.print("Enter Name: ");
        String name = sc.nextLine();

        System.out.print("Enter Age: ");
        int age = sc.nextInt();
        sc.nextLine();

        System.out.print("Enter Grade: ");
        String grade = sc.nextLine();

        studentList.add(new Student(id, name, age, grade));
        System.out.println("Student added successfully!");
    }

    // View
    static void viewStudents() {
        if (studentList.isEmpty()) {
            System.out.println("No records found.");
            return;
        }
        for (Student s : studentList) {
            s.display();
        }
    }

    // Update
    static void updateStudent() {
        System.out.print("Enter ID to update: ");
        int id = sc.nextInt();
        sc.nextLine();

        for (Student s : studentList) {
            if (s.id == id) {
                System.out.print("Enter new Name: ");
                s.name = sc.nextLine();
                System.out.print("Enter new Age: ");
                s.age = sc.nextInt();
                sc.nextLine();
                System.out.print("Enter new Grade: ");
                s.grade = sc.nextLine();
                System.out.println("Student updated successfully!");
                return;
            }
        }
        System.out.println("Student not found!");
    }

    // Delete
    static void deleteStudent() {
        System.out.print("Enter ID to delete: ");
        int id = sc.nextInt();
        sc.nextLine();

        for (Student s : studentList) {
            if (s.id == id) {
                studentList.remove(s);
                System.out.println("Student deleted successfully!");
                return;
            }
        }
        System.out.println("Student not found!");
    }

    // Search
    static void searchStudent() {
        System.out.println("Search by: 1. Name  2. Grade");
        int option = sc.nextInt();
        sc.nextLine();

        boolean found = false;

        if (option == 1) {
            System.out.print("Enter Name: ");
            String name = sc.nextLine();
            for (Student s : studentList) {
                if (s.name.equalsIgnoreCase(name)) {
                    s.display();
                    found = true;
                }
            }
        } else if (option == 2) {
            System.out.print("Enter Grade: ");
            String grade = sc.nextLine();
            for (Student s : studentList) {
                if (s.grade.equalsIgnoreCase(grade)) {
                    s.display();
                    found = true;
                }
            }
        }

        if (!found) {
            System.out.println("No matching records found.");
        }
    }
}