std.java

import java.util.*;
class Student {
    String name;
    int rollNumber;
    float marks;

    public Student(String name, int rollNumber, float marks) {
        this.name = name;
        this.rollNumber = rollNumber;
        this.marks = marks;
    }

    public void display() {
        System.out.println("Name: " + name + ", Roll Number: " + rollNumber + ", Marks: " + marks);
    }
}

class StudentManagement {
    private static Student[] students = new Student[100];
    private static int count = 0;  // To track the number of students added

    // Method to add a new student
    public static void addStudent(String name, int rollNumber, float marks) {
        students[count++] = new Student(name, rollNumber, marks);
    }

    // Method to view all students
    public static void viewStudents() {
        if (count == 0) {
            System.out.println("No students to display!");
        } else {
            for (int i = 0; i < count; i++) {
                students[i].display();
            }
        }
    }

    // Method to search student by roll number
    public static void searchStudent(int rollNumber) {
        for (int i = 0; i < count; i++) {
            if (students[i].rollNumber == rollNumber) {
                students[i].display();
                return;
            }
        }
        System.out.println("Student with Roll Number " + rollNumber + " not found.");
    }

    // Method to delete student
    public static void deleteStudent(int rollNumber) {
        for (int i = 0; i < count; i++) {
            if (students[i].rollNumber == rollNumber) {
                for (int j = i; j < count - 1; j++) {
                    students[j] = students[j + 1];
                }
                students[--count] = null;  // Reduce count and clear last slot
                System.out.println("Student with Roll Number " + rollNumber + " deleted.");
                return;
            }
        }
        System.out.println("Student with Roll Number " + rollNumber + " not found.");
    }
}

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int choice;

        do {
            System.out.println("\n=== Student Management System ===");
            System.out.println("1. Add Student");
            System.out.println("2. View All Students");
            System.out.println("3. Search Student by Roll Number");
            System.out.println("4. Delete Student by Roll Number");
            System.out.println("5. Exit");
            System.out.print("Enter your choice: ");
            choice = sc.nextInt();

            switch (choice) {
                case 1:
                    System.out.print("Enter Name: ");
                    String name = sc.next();
                    System.out.print("Enter Roll Number: ");
                    int rollNumber = sc.nextInt();
                    System.out.print("Enter Marks: ");
                    float marks = sc.nextFloat();
                    StudentManagement.addStudent(name, rollNumber, marks);
                    break;
                case 2:
                    StudentManagement.viewStudents();
                    break;
                case 3:
                    System.out.print("Enter Roll Number to Search: ");
                    int searchRollNumber = sc.nextInt();
                    StudentManagement.searchStudent(searchRollNumber);
                    break;
                case 4:
                    System.out.print("Enter Roll Number to Delete: ");
                    int deleteRollNumber = sc.nextInt();
                    StudentManagement.deleteStudent(deleteRollNumber);
                    break;
                case 5:
                    System.out.println("Exiting...");
                    break;
                default:
                    System.out.println("Invalid choice! Please try again.");
            }
        } while (choice != 5);

        sc.close();
    }
}