﻿ Java - Convert a hexadecimal to a octal number

# Java: Convert a hexadecimal to a octal number

## Java Basic: Exercise-30 with Solution

Write a Java program to convert a hexadecimal value into an octal 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.

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

Test Data:

Pictorial Presentation: Hexadecimal to Octal number

Sample Solution:

Java Code:

``````import java.util.Scanner;

public class Main {
// Function to convert a hexadecimal string to a decimal integer
public static int hex_to_oct(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 octal_num[] = new int[100];
Scanner in = new Scanner(System.in);

// Prompt the user to input a hexadecimal number
hexdec_num = in.nextLine();

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

// Convert the decimal number to octal
while (dec_num != 0) {
octal_num[i++] = dec_num % 8;
dec_num = dec_num / 8;
}

// Display the equivalent octal number
System.out.print("Equivalent of octal number is: ");
for (j = i - 1; j > 0; j--) {
System.out.print(octal_num[j]);
}

System.out.print("\n");
}
}
```
```

Explanation:

In the exercise above -

• First, it defines a method "hex_to_oct()" that takes a hexadecimal string 's' as input and converts it to its decimal equivalent. It initializes a string 'digits' containing the hexadecimal digits (0-9 and A-F), ensures that the input string 's' is in uppercase, and iterates through the characters to compute the decimal value.
• 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_oct ()" method, passing 'hexdec_num' as an argument, to convert the hexadecimal string to its decimal equivalent and stores it in the 'dec_num' variable.
• Then, it converts the decimal number to octal:
• It initializes an integer array 'octal_num' to store the octal digits.
• It enters a loop to perform the decimal-to-octal conversion:
• In each iteration, it calculates the remainder when 'dec_num' is divided by 8 (which gives the least significant octal digit).
• It stores this remainder in the 'octal_num' array.
• It updates 'dec_num' by dividing it by 8 to move to the next octal digit.
• It uses 'i' to keep track of each octal digit's position.
• Finally, it prints the octal representation of the original hexadecimal number by iterating through the 'octal_num' array in reverse order (from the most significant digit to the least significant digit).

Sample Output:

```Input a hexadecimal number: 40
Equivalent of octal number is: 100
```

Flowchart:

Java Code Editor:

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.

﻿