Convert hexadecimal to decimal – java api, iterative & recursive

Leave a Comment / By Yogesh / September 13, 2016

Given a hexadecimal number, convert hexadecimal number to decimal number using java.
We will discuss various methods to convert hexadecimal number to decimal.
- Convert hexadecimal to decimal using Integer class
  - Integer.parseInt
- Iterative program to convert hexadecimal number to decimal.
- Recursive program to convert hexadecimal number to decimal.

Methods – Convert hexadecimal number to integer in java

1.) Convert hexadecimal to decimal using Integer.parseInt

private static int toHexUsingParseInt(String number) {
    return Integer.parseInt(number, 16);
}

2.) Convert hexadecimal to decimal number – iterative

private static int iterative(String hexNumber) {
    int power = 0;
    int decimal = 0;
    hexNumber = hexNumber.toUpperCase();
    int length = hexNumber.length();
    String hexCode = "0123456789ABCDEF";
    for (int index = 0; index < length; index++) {
        char digit = hexNumber.charAt(length - index - 1);
        decimal = decimal + hexCode.indexOf(digit) * (int) Math.pow(16, power++);
    }
    return decimal;
}

3.) Convert hexadecimal to decimal number – recursive

private static int recursive(String hexNumber) {
    int decimal = 0;
    String hexCode = "0123456789ABCDEF";
    hexNumber = hexNumber.toUpperCase();
    int length = hexNumber.length();
    if (length > 0) {
        char ch = hexNumber.charAt(0);
        int digit = hexCode.indexOf(ch);
        String substring = hexNumber.substring(1);
        decimal = digit * (int) Math.pow(16, length - 1) + recursive(substring);
    }
    return decimal;
}

Complete program to convert hexadecimal to decimal number

package org.learn;
 
import java.util.Scanner;
 
public class HexaDecimalToDecimal {
 
    public static void main(String[] args) {
        try (Scanner scanner = new Scanner(System.in)) {
 
            System.out.printf("1. Enter hexadecimal string : ");
            String hex = scanner.next();
 
            int decimal = toHexUsingParseInt(hex);
            System.out.printf("2. Hex to decimal - parseInt(%s,16) = %d ", hex, decimal);
 
            decimal = iterative(hex);
            System.out.printf("\n3. Hex to decimal - iterative(%s) = %d ", hex, decimal);
 
            decimal = recursive(hex);
            System.out.printf("\n4. Hex to decimal - recursive(%s) = %d ", hex, decimal);
        }
    }
 
    private static int toHexUsingParseInt(String number) {
        return Integer.parseInt(number, 16);
    }
 
private static int iterative(String hexNumber) {
    int power = 0;
    int decimal = 0;
    hexNumber = hexNumber.toUpperCase();
    int length = hexNumber.length();
    String hexCode = "0123456789ABCDEF";
    for (int index = 0; index < length; index++) {
        char digit = hexNumber.charAt(length - index - 1);
        decimal = decimal + hexCode.indexOf(digit) * (int) Math.pow(16, power++);
    }
    return decimal;
}
 
    private static int recursive(String hexNumber) {
        int decimal = 0;
        String hexCode = "0123456789ABCDEF";
        hexNumber = hexNumber.toUpperCase();
        int length = hexNumber.length();
        if (length > 0) {
            char ch = hexNumber.charAt(0);
            int digit = hexCode.indexOf(ch);
            String substring = hexNumber.substring(1);
            decimal = digit * (int) Math.pow(16, length - 1) + recursive(substring);
        }
        return decimal;
    }
}

Program output – convert hexadecimal to decimal number

Enter hexadecimal string : 1234
Hex to decimal - parseInt(1234,16) = 4660 
Hex to decimal - iterative(1234) = 4660 
Hex to decimal - recursive(1234) = 4660 
 
Enter hexadecimal string : 1a2B3
Hex to decimal - parseInt(1a2B3,16) = 107187 
Hex to decimal - iterative(1a2B3) = 107187 
Hex to decimal - recursive(1a2B3) = 107187 
 
Enter hexadecimal string : abcd
Hex to decimal - parseInt(abcd,16) = 43981 
Hex to decimal - iterative(abcd) = 43981 
Hex to decimal - recursive(abcd) = 43981 