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

Simple:

  public static String decToHex(int dec)
  {
        return Integer.toHexString(dec);
  }

As mentioned here: Java Convert integer to hex integer

Answer 2

A better solution to convert Decimal To HexaDecimal and this one is less complex

import java.util.Scanner;
public class DecimalToHexa
{
    public static void main(String ar[])
    {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter a Decimal number: ");
        int n=sc.nextInt();
        if(n<0)
        {
            System.out.println("Enter a positive integer");
            return;
        }
        int i=0,d=0;
        String hx="",h="";
        while(n>0)
        {
            d=n%16;`enter code here`
            n/=16;
            if(d==10)h="A";
            else if(d==11)h="B";
            else if(d==12)h="C";
            else if(d==13)h="D";
            else if(d==14)h="E";
            else if(d==15)h="F";
            else h=""+d;            
            hx=""+h+hx;
        }
        System.out.println("Equivalent HEXA: "+hx);
    }
}        

Answer 3

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);

Answer 4

The following converts decimal to Hexa Decimal with Time Complexity : O(n) Linear Time with out any java inbuilt function

private static String decimalToHexaDecimal(int N) {
    char hexaDecimals[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
    StringBuilder builder = new StringBuilder();
    int base= 16;
    while (N != 0) {
        int reminder = N % base;
        builder.append(hexaDecimals[reminder]);
        N = N / base;
    }

    return builder.reverse().toString();
}

Answer 5

Code to convert DECIMAL -to-> BINARY, OCTAL, HEXADECIMAL

public class ConvertBase10ToBaseX {
    enum Base {
        /**
         * Integer is represented in 32 bit in 32/64 bit machine.
         * There we can split this integer no of bits into multiples of 1,2,4,8,16 bits
         */
        BASE2(1,1,32), BASE4(3,2,16), BASE8(7,3,11)/* OCTAL*/, /*BASE10(3,2),*/ 
        BASE16(15, 4, 8){       
            public String getFormattedValue(int val){
                switch(val) {
                case 10:
                    return "A";
                case 11:
                    return "B";
                case 12:
                    return "C";
                case 13:
                    return "D";
                case 14:
                    return "E";
                case 15:
                    return "F";
                default:
                    return "" + val;
                }

            }
        }, /*BASE32(31,5,1),*/ BASE256(255, 8, 4), /*BASE512(511,9),*/ Base65536(65535, 16, 2);

        private int LEVEL_0_MASK;
        private int LEVEL_1_ROTATION;
        private int MAX_ROTATION;

        Base(int levelZeroMask, int levelOneRotation, int maxPossibleRotation) {
            this.LEVEL_0_MASK = levelZeroMask;
            this.LEVEL_1_ROTATION = levelOneRotation;
            this.MAX_ROTATION = maxPossibleRotation;
        }

        int getLevelZeroMask(){
            return LEVEL_0_MASK;
        }
        int getLevelOneRotation(){
            return LEVEL_1_ROTATION;
        }
        int getMaxRotation(){
            return MAX_ROTATION;
        }
        String getFormattedValue(int val){
            return "" + val;
        }
    }

    public void getBaseXValueOn(Base base, int on) {
        forwardPrint(base, on);
    }

    private void forwardPrint(Base base, int on) {

        int rotation = base.getLevelOneRotation();
        int mask = base.getLevelZeroMask();
        int maxRotation = base.getMaxRotation();
        boolean valueFound = false;

        for(int level = maxRotation; level >= 2; level--) {
            int rotation1 = (level-1) * rotation;
            int mask1 = mask << rotation1 ;
            if((on & mask1) > 0 ) {
                valueFound = true;
            }
            if(valueFound)
            System.out.print(base.getFormattedValue((on & mask1) >>> rotation1));
        }
        System.out.println(base.getFormattedValue((on & mask)));
    }

    public int getBaseXValueOnAtLevel(Base base, int on, int level) {
        if(level > base.getMaxRotation() || level < 1) {
            return 0; //INVALID Input
        }
        int rotation = base.getLevelOneRotation();
        int mask = base.getLevelZeroMask();

        if(level > 1) {
            rotation = (level-1) * rotation;
            mask = mask << rotation;
        } else {
            rotation = 0;
        }


        return (on & mask) >>> rotation;
    }

    public static void main(String[] args) {
        ConvertBase10ToBaseX obj = new ConvertBase10ToBaseX();

        obj.getBaseXValueOn(Base.BASE16,12456); 
//      obj.getBaseXValueOn(Base.BASE16,300); 
//      obj.getBaseXValueOn(Base.BASE16,7); 
//      obj.getBaseXValueOn(Base.BASE16,7);

        obj.getBaseXValueOn(Base.BASE2,12456);
        obj.getBaseXValueOn(Base.BASE8,12456);
        obj.getBaseXValueOn(Base.BASE2,8);
        obj.getBaseXValueOn(Base.BASE2,9);
        obj.getBaseXValueOn(Base.BASE2,10);
        obj.getBaseXValueOn(Base.BASE2,11);
        obj.getBaseXValueOn(Base.BASE2,12);
        obj.getBaseXValueOn(Base.BASE2,13);
        obj.getBaseXValueOn(Base.BASE2,14);
        obj.getBaseXValueOn(Base.BASE2,15);
        obj.getBaseXValueOn(Base.BASE2,16);
        obj.getBaseXValueOn(Base.BASE2,17);


        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE2, 4, 1)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE2, 4, 2)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE2, 4, 3)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE2, 4, 4)); 

        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE16,15, 1)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE16,30, 2)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE16,7, 1)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE16,7, 2)); 

        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE256, 511, 1)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE256, 511, 2)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE256, 512, 1));
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE256, 512, 2)); 
        System.out.println(obj.getBaseXValueOnAtLevel(Base.BASE256, 513, 2)); 


    }
}

Answer 6

I will use

Long a = Long.parseLong(cadenaFinal, 16 );

since there is some hex that can be larguer than intenger and it will throw an exception