Convert decimal number to hexdecimal – (java api, iterative & recursive)

Leave a Comment / By Yogesh / May 19, 2020

Given a decimal number (base 10), convert decimal number to hexadecimal (base 16) using java.
We will discuss various methods to convert decimal integer to hexadecimal.
1. Convert decimal to hexadecimal using Integer class
  - Integer.toHexString(int number)
  - Integer.toString(int number, int radix)
2. Iterative program to convert decimal integer to hexadecimal number.
3. Recursive method to convert decimal integer to hexadecimal number.

Java JDK methods to convert decimal to hexadecimal:

Method Name	Description
String toHexString(int i)	Returns a string representation of the integer argument as an unsigned integer in base 16.
String toString(int i, int radix)	Returns a string representation of the first argument in the radix specified by the second argument.

Methods to convert decimal integer to hexadecimal :

1.) Convert decimal to hexadecimal using Integer.toHexString

private static final String toHexString(int number) {
    return Integer.toHexString(number).toUpperCase();
}

2.) Convert decimal to hexadecimal using Integer.toString

private static final String toString(int number) {
    return Integer.toString(number,16).toUpperCase();
}

3.) Convert decimal to hexadecimal using iterative method

private static String iterative(int number) {
 
    StringBuilder builder = new StringBuilder();
    while (number > 0) {
        int remainder = number % 16;
        char hexCode = hexCodes[remainder];
        builder.append(hexCode);
        number = number / 16;
    }
    return builder.reverse().toString();
}

4.) Convert decimal to hexadecimal using recursive method

private static String recursive(int number) {
    StringBuilder builder = new StringBuilder();
 
    if (number > 0) {
        String hexNumber = recursive(number / 16);
        int digit = number % 16;
        char hexDigit = hexCodes[digit];
        builder.append(hexNumber + hexDigit);
    }
    return builder.toString();
}

Complete program to convert decimal number to hexadecimal

package org.learn;
 
import java.util.Scanner;
 
public class DecimalToHex {
    private static char[] hexCodes = {'0', '1', '2', '3', '4',
            '5', '6', '7', '8', '9',
            'A', 'B', 'C', 'D', 'E', 'F'};
 
    private static String iterative(int number) {
 
        StringBuilder builder = new StringBuilder();
        while (number > 0) {
            int remainder = number % 16;
            char hexCode = hexCodes[remainder];
            builder.append(hexCode);
            number = number / 16;
        }
        return builder.reverse().toString();
    }
 
    private static String recursive(int number) {
        StringBuilder builder = new StringBuilder();
 
        if (number > 0) {
            String hexNumber = recursive(number / 16);
            int digit = number % 16;
            char hexDigit = hexCodes[digit];
            builder.append(hexNumber + hexDigit);
        }
        return builder.toString();
    }
 
    private static final String toString(int number) {
        return Integer.toString(number,16).toUpperCase();
    }
 
    private static final String toHexString(int number) {
        return Integer.toHexString(number).toUpperCase();
    }
    public static void main(String[] args) {
        try (Scanner scanner = new Scanner(System.in)) {
            System.out.printf("1. Enter decimal number : ");
            int number = scanner.nextInt();
            String hex = toHexString(number);
 
            System.out.printf("2. Hex of (%d) using toHexString method = %s\n", number, hex);
 
            hex = toString(number);
            System.out.printf("3. Hex of (%d) using toString method = %s\n", number, hex);
 
            hex = iterative(number);
            System.out.printf("4. Hex of (%d) using iterative method = %s\n", number, hex);
 
            hex = recursive(number);
            System.out.printf("5. Hex of (%d) using recursive method = %s\n", number, hex);
        }
    }
}

Program output – convert decimal number to hexadecimal

Enter decimal number : 100
Hex of (100) using toHexString method = 64
Hex of (100) using toString method = 64
Hex of (100) using iterative method = 64
Hex of (100) using recursive method = 64
 
Enter decimal number : 255
Hex of (255) using toHexString method = FF
Hex of (255) using toString method = FF
Hex of (255) using iterative method = FF
Hex of (255) using recursive method = FF