NumberSystemConverter.java

import java.util.Scanner;

public class NumberSystemConverter {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        while (true) {

            System.out.println("\n=================================");
            System.out.println("     NUMBER SYSTEM CONVERTER");
            System.out.println("=================================");
            System.out.println("1. Decimal → Binary");
            System.out.println("2. Decimal → Octal");
            System.out.println("3. Decimal → Hexadecimal");
            System.out.println("4. Convert All");
            System.out.println("5. Exit");

            System.out.print("\nEnter your choice: ");
            int choice = sc.nextInt();

            if (choice == 5) {
                System.out.println("\nThank you for using the converter! 👋");
                break;
            }

            if (choice >= 1 && choice <= 4) {

                System.out.print("Enter a decimal number: ");
                int number = sc.nextInt();

                switch (choice) {

                    case 1:
                        System.out.println(
                                "Binary: " +
                                Integer.toBinaryString(number)
                        );
                        break;

                    case 2:
                        System.out.println(
                                "Octal: " +
                                Integer.toOctalString(number)
                        );
                        break;

                    case 3:
                        System.out.println(
                                "Hexadecimal: " +
                                Integer.toHexString(number).toUpperCase()
                        );
                        break;

                    case 4:
                        System.out.println("\nDecimal: " + number);

                        System.out.println(
                                "Binary: " +
                                Integer.toBinaryString(number)
                        );

                        System.out.println(
                                "Octal: " +
                                Integer.toOctalString(number)
                        );

                        System.out.println(
                                "Hexadecimal: " +
                                Integer.toHexString(number).toUpperCase()
                        );
                        break;
                }

            } else {
                System.out.println("❌ Invalid choice!");
            }
        }

        sc.close();
    }
}