BitwiseMasks-App

import java.util.Scanner;

public class Program {
    public static boolean containsBit(int mask, int el) {
        return ((mask & (1 << el)) != 0) ? true : false;
    }

    public static int insertBit(int mask, int el) {
        return (mask | (1 << el));
    }

    public static int eraseBit(int mask, int el) {
        return (mask & ~(1 << el));
    }

    public static int changeBit(int mask, int el) {
        return (mask ^ (1 << el));
    }

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int prisustviq = 0;

        while (true) {
            System.out.println("1. Print");
            System.out.println("2. Napishi prisustvie");
            System.out.println("3. Premahni prisustvie");
            System.out.println("4. Promeni prisustvie");
            System.out.println("5. to Exit");
            System.out.print("Enter option: ");
            String input = scan.nextLine();

            if (input.charAt(0) == '5') {
                break;
            } else if (input.charAt(0) == '1') {
                for (int i = 0; i < 32; i++) {
                    System.out.print("Student #" + (i+1) + " : ");
                    if (containsBit(prisustviq, i)) {
                        System.out.println("TUK");
                    } else {
                        System.out.println("OTSUSTVA");
                    }
                }
            } else if (input.charAt(0) == '2') {
                System.out.print("Enter student number: ");
                int num = Integer.parseInt(scan.nextLine());
                prisustviq = insertBit(prisustviq, num);
            } else if (input.charAt(0) == '3') {
                System.out.print("Enter student number: ");
                int num = Integer.parseInt(scan.nextLine());
                prisustviq = eraseBit(prisustviq, num);
            } else if (input.charAt(0) == '4') {
                System.out.print("Enter student number: ");
                int num = Integer.parseInt(scan.nextLine());
                prisustviq = changeBit(prisustviq, num);
            } else {
                System.out.println("Invalid option!");
            }
        }
    }
}