Java: Convert a decimal number to hexadecimal number

Last update on May 12 2025 13:17:54 (UTC/GMT +8 hours)

Decimal to Hexadecimal Converter

Write a Java program to convert a decimal number to a hexadecimal number.

Decimal number: The decimal numeral system is the standard system for denoting integer and non-integer numbers. It is also called base-ten positional numeral system.

Hexadecimal number: Hexadecimal is a positional numeral system with a radix, or base, of 16. It 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.

Test Data:
Input a decimal number: 15

Pictorial Presentation: Decimal to Hexadecimal number

Sample Solution:

Java Code:

import java.util.Scanner;

public class Exercise20 {
    public static void main(String args[]) {
        // Declare variables to store decimal number and remainder
        int dec_num, rem;
        
        // Initialize an empty string for the hexadecimal number
        String hexdec_num = "";
        
        // Define the hexadecimal number digits
        char hex[] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
        
        // Create a Scanner object to read input from the user
        Scanner in = new Scanner(System.in);

        // Prompt the user to input a decimal number
        System.out.print("Input a decimal number: ");
        dec_num = in.nextInt();

        // Convert the decimal number to hexadecimal
        while (dec_num > 0) {
            rem = dec_num % 16;
            hexdec_num = hex[rem] + hexdec_num;
            dec_num = dec_num / 16;
        }
        
        // Display the hexadecimal representation of the decimal number
        System.out.print("Hexadecimal number is: " + hexdec_num + "\n");
    }
}

Explanation:

In the exercise above -

• It takes a decimal number ('dec_num') as input from the user using the "Scanner" class.
• It initializes an empty string 'hexdec_num' to store the hexadecimal representation and defines an array 'hex' containing hexadecimal digits (0-9 and A-F).
• It enters a loop to perform the decimal-to-hexadecimal conversion:
• In each iteration, it calculates the remainder of 'dec_num' when divided by 16 (which gives the hexadecimal digit) and appends it to the 'hexdec_num' string.
• It then updates 'dec_num' by dividing it by 16.
• The loop continues until 'dec_num' becomes zero, effectively converting the entire decimal number to hexadecimal.
• After the loop, it prints the hexadecimal representation of the decimal number stored in the 'hexdec_num' string.

Sample Output:

Input a decimal number: 15                                                                                    
Hexadecimal number is : F 

Flowchart:

For more Practice: Solve these Related Problems:

• Convert a large decimal number (greater than 1000) to hexadecimal.
• Modify the program to allow the user to input multiple decimal numbers for conversion.
• Write a program to convert a decimal number to a hexadecimal number without using built-in functions.
• Convert a floating-point decimal number to a hexadecimal representation.

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