Java: Convert a octal number to a hexadecimal number

Last update on May 12 2025 13:19:54 (UTC/GMT +8 hours)

Octal to Hexadecimal Converter

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

Octal number: The octal numeral system is the base-8 number system, and uses the digits 0 to 7.

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.

Test Data:
Input any octal number: 100

Pictorial Presentation: Octal to Hexadecimal number

Sample Solution:

Java Code:

public class Exercise27 {
    public static void main(String args[]) {
        // Declare variables to store octal number and its decimal and hexadecimal equivalents
        String octal_num, hex_num;
        int decnum;
        
        // Create a Scanner object to read input from the user
        Scanner in = new Scanner(System.in);
        
        // Prompt the user to input an octal number
        System.out.print("Input an octal number : ");
        octal_num = in.nextLine();
        
        // Convert the octal number to its decimal equivalent using parseInt
        decnum = Integer.parseInt(octal_num, 8);
        
        // Convert the decimal number to its hexadecimal equivalent
        hex_num = Integer.toHexString(decnum);
        
        // Display the equivalent hexadecimal number
        System.out.print("Equivalent hexadecimal number: " + hex_num + "\n");
    }
}

Explanation:

In the exercise above -

• First, it takes an octal number as input from the user using the "Scanner" class and stores it as a string in the variable 'octal_num'.
• It uses the "Integer.parseInt()" method to convert the 'octal_num' string to an integer 'decnum', specifying base 8 (octal) as the input radix.
• It then uses the "Integer.toHexString()" method to convert the 'decnum' to its hexadecimal representation and stores it in the 'hex_num' string.
• Finally, it prints the hexadecimal representation of the original octal number stored in the 'hex_num' variable.

Sample Output:

Input a octal number : 100                                                                                    
Equivalent hexadecimal number: 40 

Flowchart:

For more Practice: Solve these Related Problems:

• Convert an octal number with more than four digits to hexadecimal.
• Modify the program to convert multiple octal numbers at once.
• Write a program that validates the user input before performing the conversion.
• Implement octal-to-hexadecimal conversion without converting to decimal first.

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