Question

Write a program to convert the input numbers to another number system.

1. Decimal to Binary

2. Binary to Decimal

3. Hexadecimal to Decimal

4. Decimal to Hexadecimal

5. Binary to Hexadecimal

6. Hexadecimal to Binary

The user will type in the input number as following:

Binary number : up to 8 bits

Hexadecimal number: up to 2 bytes

Decimal number: Less than 256

As a result, print out the output after the conversion with their input numbers.

The program must repeat the procedure until the user wants to stop the program

Answer 1

Following is the program written in JAVA to perform the conversions.

• This program utilizes the in-built functions of java.lang.Integer class for most of the conversions (due to time constraint), but also illustrates the division method for decimal to binary conversion.
• A similar approach could be used for conversion to hexadecimal, where an array of 16 symbols of hex radix (namely 0-9 and a-f) can be taken and utilized in the division method.

Code:

==========================================================================================

import java.util.Scanner;

public class NumberConversionDemo {
  
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        NumberConverter nc = new NumberConverter();

        Integer option = null;
        String num = null;
        do {
            System.out.println("Welcome to the number converter. Please select a number to execute the option in front of it:\n");
            System.out.println("1. Decimal to Binary\n");
            System.out.println("2. Binary to Decimal\n");
            System.out.println("3. Hexadecimal to Decimal\n");
            System.out.println("4. Decimal to Hexadecimal\n");
            System.out.println("5. Binary to Hexadecimal\n");
            System.out.println("6. Hexadecimal to Binary\n");
            System.out.println("Press 0 to exit\n");

            option = Integer.parseInt(sc.nextLine());

            switch(option) {
                case 0:     sc.close();
                            return;

                default:    System.out.println("Please enter the number to be converted.\n");
                            num = sc.nextLine();
                            System.out.println(nc.convert(num, option));
                            sc.nextLine();

            }

            System.out.println("\n\n\n=============================================================================================");

        }
        while(true);
    }
}

class NumberConverter {

    private Integer number;

    public String convert(String num, Integer option) {
        switch(option) {
            case 1: return convertDecToBin(num);

            case 2: return convertBinToDec(num);

            case 3: return convertHexToDec(num);

            case 4: return convertDecToHex(num);

            case 5: return convertBinToHex(num);

            case 6: return convertHexToBin(num);
        }
        return "Invalid option. Please try again.\n";
    }

    public String convertDecToBin(String num) {
        this.number = Integer.parseInt(num);
        if(this.number > 256) {
            return "Invalid input or number out of range. Please try again.\n";
        }
        String revNum = "";
        Integer rem;
        while (this.number>0) {
            rem = this.number % 2;
            revNum = revNum + "" + rem;
            this.number = this.number/2;
        }
        StringBuilder sb = new StringBuilder(revNum);
        return "Input: " + num + "\nOutput: " + sb.reverse().toString();
    }

    public String convertBinToDec(String num) {
        if(num.matches("(.*)[2-9](.*)") || num.length() > 8) {
            return "Invalid input or number out of range. Please try again.\n";
        }
        return "Input: " + num + "\nOutput: " + Integer.parseInt(num, 2);
    }

    public String convertHexToDec(String num) {
        num = num.toLowerCase();
        if(num.matches("(.*)[g-zG-Z](.*)") || num.length() > 4) {
            return "Invalid input or number out of range. Please try again.\n";
        }
        return "Input: " + num + "\nOutput: " + Integer.parseInt(num, 16);
    }

    public String convertDecToHex(String num) {
        this.number = Integer.parseInt(num);
        if(this.number > 256) {
            return "Invalid input or number out of range. Please try again.\n";
        }
        return "Input: " + num + "\nOutput: " + Integer.toHexString(this.number);
    }

    public String convertBinToHex(String num) {
        if(num.matches("(.*)[2-9](.*)") || num.length() > 8) {
            return "Invalid input or number out of range. Please try again.\n";
        }
        return "Input: " + num + "\nOutput: " + Integer.toHexString(Integer.parseInt(num, 2));
    }

    public String convertHexToBin(String num) {
        num = num.toLowerCase();
        if(num.matches("(.*)[g-zG-Z](.*)") || num.length() > 4) {
            return "Invalid input or number out of range. Please try again.\n";
        }
        return "Input: " + num + "\nOutput: " + Integer.toBinaryString(Integer.parseInt(num, 16));
    }
}