Java: Convert a hexadecimal to a binary number

Java Basic: Exercise-29 with Solution

Write a Java program to convert a hexadecimal number into a binary number.

Hexadecimal number: This is a positional numeral system with a radix, or base, of 16. Hexadecimal uses sixteen distinct symbols, most often the symbols 0-9 to represent values zero to nine, and A, B, C, D, E, F (or alternatively a, b, c, d, e, f) to represent values ten to fifteen.

Binary number: A binary number is a number expressed in the base-2 numeral system or binary numeral system. This system uses only two symbols: typically 1 (one) and 0 (zero).

Test Data:
Input any hexadecimal number: 37

Pictorial Presentation: Hexadecimal to Binary number

Java: Convert a hexadecimal to a binary number

Sample Solution:

Java Code:

import java.util.Scanner;

public class Exercise29 {
    // Function to convert a hexadecimal string to a decimal integer
    public static int hex_to_binary(String s) {
        // Define a string containing hexadecimal digits
        String digits = "0123456789ABCDEF";
        s = s.toUpperCase(); // Convert the input string to uppercase
        int val = 0; // Initialize the decimal value to 0

        // Iterate through each character in the input string
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i); // Get the current character
            int d = digits.indexOf(c); // Find the index of the character in the digits string
            val = 16 * val + d; // Update the decimal value using hexadecimal conversion

        return val; // Return the decimal value

    public static void main(String args[]) {
        String hexdec_num;
        int dec_num, i = 1, j;
        int bin_num[] = new int[100];
        Scanner scan = new Scanner(System.in);

        // Prompt the user to enter a hexadecimal number
        System.out.print("Enter Hexadecimal Number : ");
        hexdec_num = scan.nextLine();

        // Call the hex_to_binary function to convert the hexadecimal number to decimal
        dec_num = hex_to_binary(hexdec_num);

        // Convert the decimal number to binary
        while (dec_num != 0) {
            bin_num[i++] = dec_num % 2;
            dec_num = dec_num / 2;

        // Display the equivalent binary number
        System.out.print("Equivalent Binary Number is: ");
        for (j = i - 1; j > 0; j--) {



In the exercise above -

  • First, it defines a method "hex_to_decimal()" that takes a hexadecimal string 's' as input and converts it to its decimal equivalent.
  • The method initializes a string 'digits' containing the hexadecimal digits (0-9 and A-F) and ensures that the input string 's' is in uppercase to handle both uppercase and lowercase hexadecimal characters.
  • It initializes an integer variable 'val' to store the decimal value.
  • Next it iterates through each character 'c' in the input string 's' and finds the corresponding decimal value 'd' by looking up the index of 'c' in the 'digits' string.
  • It updates the 'val' by multiplying it by 16 and adding the decimal value 'd'.
  • The method returns the final decimal value 'val'.
  • In the "main()" function, it takes a hexadecimal number as input from the user using the "Scanner" class and stores it in the 'hexdec_num' string.
  • It calls the "hex_to_decimal()" method, passing 'hexdec_num' as an argument, to convert the hexadecimal string to its decimal equivalent and stores it in the 'dec_num' variable.
  • Finally, it prints the decimal representation of the original hexadecimal number stored in the 'dec_num' variable.

Sample Output:

Enter Hexadecimal Number : 37                                                                                 
Equivalent Binary Number is: 110111


Flowchart: Java exercises: Convert a hexadecimal to a binary number

Java Code Editor:

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