Question

JAVA PLEASE

4. Write a recursive program that converts a Hex base value to its decimal equivalent. This program must validate the ueser’s input. You program must have the main method, inputValidate method and hexToDecimal method. Must implement the last method recursively.

Here is a sample output.

Enter a valid hex number: 10 Your number in decimal is: 16 Do you have another number: yes Enter a valid hex number: 123 Your number in decimal is: 291 Do you have another number: yes Enter a valid hex number: 111 Your number in decimal is: 273 Do you have another number: yes Enter a valid hex number: num Enter a valid hex number: EF Your number in decimal is: 239 Do you have another number: no

Answer 1

import java.util.Scanner;

public class HexNumber {

    public static long hexToDecimal(String hexString) {
        if(hexString.isEmpty()) {
            return 0;
        }
        
        int dec = 0;
        char c = hexString.charAt(hexString.length() - 1);
        if(c <= '9') {
            dec = dec*16 + (c - '0');
        } else {
            dec = dec*16 + (10 + (c - 'A'));
        }
        
        return dec + 16 * hexToDecimal(hexString.substring(0, hexString.length() - 1));
    }

    public static boolean checkValidHexaChar(char c) {
        return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F');
    }
    
    public static boolean inputValidate(String hex) {
        for (int i = 0; i < hex.length(); i++) {
            // take every char from the input one by one
            char c = hex.charAt(i);
            // check the validity of each char
            if(!checkValidHexaChar(c)) {
                return false;
            }
        }
        return true;
    }
    
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        String choice;
        do {
            String hex;
            do {
                System.out.println("Enter a valid hex number: ");
                hex = in.nextLine().toUpperCase();
            } while(!inputValidate(hex));
            
            System.out.println("Your number in decimal is: " + hexToDecimal(hex));
            
            System.out.println("Do you have another number(yes/no): ");
            choice = in.nextLine().toLowerCase();
        } while (choice.equals("yes"));
        in.close();
    }

}

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