Decimal to Hexadecimal Converter in Java

Question

I have a homework assignment where I need to do three-way conversion between decimal, binary and hexadecimal. The function I need help with is converting a decimal into a hexadecimal. I have nearly no understanding of hexadecimal, nonetheless how to convert a decimal into hex. I need a function that takes in an int dec and returns a String hex. Unfortunately I don't have any draft of this function, I'm completely lost. All I have is this.

  public static String decToHex(int dec)
  {
    String hex = "";


    return hex;
  }

Also I can't use those premade functions like Integer.toHexString() or anything, I need to actually make the algorithm or I wouldn't have learned anything.

Answer 1

I need a function that takes in an int dec and returns a String hex.

I found a more elegant solution from http://introcs.cs.princeton.edu/java/31datatype/Hex2Decimal.java.html . I changed a bit from the original ( see the edit )

// precondition:  d is a nonnegative integer
public static String decimal2hex(int d) {
    String digits = "0123456789ABCDEF";
    if (d <= 0) return "0";
    int base = 16;   // flexible to change in any base under 16
    String hex = "";
    while (d > 0) {
        int digit = d % base;              // rightmost digit
        hex = digits.charAt(digit) + hex;  // string concatenation
        d = d / base;
    }
    return hex;
}

Disclaimer: I use this algorithm in my coding interview. I hope this solution doesn't get too popular :)

Edit June 17 2016 : I added the base variable to give the flexibility to change into any base : binary, octal, base of 7 ...
According to the comments, this solution is the most elegant so I removed the implementation of Integer.toHexString() .

Edit September 4 2015 : I found a more elegant solution http://introcs.cs.princeton.edu/java/31datatype/Hex2Decimal.java.html

Answer 2

Here's mine

public static String dec2Hex(int num)
{
    String hex = "";

    while (num != 0)
    {
        if (num % 16 < 10)
            hex = Integer.toString(num % 16) + hex;
        else
            hex = (char)((num % 16)+55) + hex;
        num = num / 16;
    }

    return hex;
}

Answer 3

Check out the code below for decimal to hexadecimal conversion,

import java.util.Scanner;

public class DecimalToHexadecimal
{
   public static void main(String[] args)
   {
      int temp, decimalNumber;
      String hexaDecimal = "";
      char hexa[] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

      Scanner sc = new Scanner(System.in);
      System.out.print("Please enter decimal number : ");
      decimalNumber = sc.nextInt();

      while(decimalNumber > 0)
      {
         temp = decimalNumber % 16;
         hexaDecimal = hexa[temp] + hexaDecimal;
         decimalNumber = decimalNumber / 16;
      }

      System.out.print("The hexadecimal value of " + decimalNumber + " is : " + hexaDecimal);      
      sc.close();
   }
}

You can learn more on different ways to convert decimal to hexadecimal in the following link >> java convert decimal to hexadecimal.

Answer 4

Here is the code for any number :

import java.math.BigInteger;

public class Testing {

/**
 * @param args
 */
static String arr[] ={"0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"}; 
public static void main(String[] args) {
    String value = "214";
    System.out.println(value + " : " + getHex(value));
}


public static String getHex(String value) {
    String output= "";
    try {
        Integer.parseInt(value);
        Integer number = new Integer(value);
        while(number >= 16){
            output = arr[number%16] + output;
            number = number/16;
        }
        output = arr[number]+output;

    } catch (Exception e) {
        BigInteger number = null;
        try{
            number = new BigInteger(value);
        }catch (Exception e1) {
            return "Not a valid numebr";
        }
        BigInteger hex = new BigInteger("16");
        BigInteger[] val = {};

        while(number.compareTo(hex) == 1 || number.compareTo(hex) == 0){
            val = number.divideAndRemainder(hex);
            output = arr[val[1].intValue()] + output;
            number = val[0];
        }
        output = arr[number.intValue()] + output;
    }

    return output;
}

}

Answer 5

Consider dec2m method below for conversion from dec to hex, oct or bin.

Sample output is

28 dec == 11100 bin 28 dec == 34 oct 28 dec == 1C hex

public class Conversion {
    public static void main(String[] argv) {
        int x = 28;                           // sample number
        if (argv.length > 0)
            x = Integer.parseInt(argv[0]);    // number from command line

        System.out.printf("%d dec == %s bin\n", i, dec2m(x, 2));
        System.out.printf("%d dec == %s oct\n", i, dec2m(x, 8));
        System.out.printf("%d dec == %s hex\n", i, dec2m(x, 16));
    }

    static String dec2m(int N, int m) {
        String s = "";
        for (int n = N; n > 0; n /= m) {
            int r = n % m;
            s = r < 10 ? r + s : (char) ('A' - 10 + r) + s;
        }
        return s;
    }
}

Answer 6

Another possible solution:

public String DecToHex(int dec){
  char[] hexDigits = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
              'A', 'B', 'C', 'D', 'E', 'F'};
  String hex = "";
  while (dec != 0) {
      int rem = dec % 16;
      hex = hexDigits[rem] + hex;
      dec = dec / 16;
  }
  return hex;
}