JavaAlgorithms/Conversions/HexToOct.java

package Conversions;

import java.util.Scanner;

/**
 * Converts any Hexadecimal Number to Octal
 *
 * @author Tanmay Joshi
 */
public class HexToOct {
  /**
   * This method converts a Hexadecimal number to a decimal number
   *
   * @param s The Hexadecimal Number
   * @return The Decimal number
   */
  public static int hex2decimal(String s) {
    String str = "0123456789ABCDEF";
    s = s.toUpperCase();
    int val = 0;
    for (int i = 0; i < s.length(); i++) {
      char a = s.charAt(i);
      int n = str.indexOf(a);
      val = 16 * val + n;
    }
    return val;
  }

  /**
   * This method converts a Decimal number to a octal number
   *
   * @param q The Decimal Number
   * @return The Octal number
   */
  public static int decimal2octal(int q) {
    int now;
    int i = 1;
    int octnum = 0;
    while (q > 0) {
      now = q % 8;
      octnum = (now * (int) (Math.pow(10, i))) + octnum;
      q /= 8;
      i++;
    }
    octnum /= 10;
    return octnum;
  }

  /**
   * Main method that gets the hex input from user and converts it into octal.
   *
   * @param args arguments
   */
  public static void main(String args[]) {
    String hexadecnum;
    int decnum, octalnum;
    Scanner scan = new Scanner(System.in);

    System.out.print("Enter Hexadecimal Number : ");
    hexadecnum = scan.nextLine();

    // first convert hexadecimal to decimal
    decnum =
        hex2decimal(
            hexadecnum); // Pass the string to the hex2decimal function and get the decimal form in
    // variable decnum

    // convert decimal to octal
    octalnum = decimal2octal(decnum);
    System.out.println("Number in octal: " + octalnum);
    scan.close();
  }
}