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

One possible solution:

import java.lang.StringBuilder;

class Test {
  private static final int sizeOfIntInHalfBytes = 8;
  private static final int numberOfBitsInAHalfByte = 4;
  private static final int halfByte = 0x0F;
  private static final char[] hexDigits = { 
    '0', '1', '2', '3', '4', '5', '6', '7', 
    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
  };

  public static String decToHex(int dec) {
    StringBuilder hexBuilder = new StringBuilder(sizeOfIntInHalfBytes);
    hexBuilder.setLength(sizeOfIntInHalfBytes);
    for (int i = sizeOfIntInHalfBytes - 1; i >= 0; --i)
    {
      int j = dec & halfByte;
      hexBuilder.setCharAt(i, hexDigits[j]);
      dec >>= numberOfBitsInAHalfByte;
    }
    return hexBuilder.toString(); 
  }

  public static void main(String[] args) {
     int dec = 305445566;
     String hex = decToHex(dec);
     System.out.println(hex);       
  }
}

Output:

1234BABE

Anyway, there is a library method for this:

String hex = Integer.toHexString(dec);