Hexadecimal and decimal convert code

[Qing Tian]

please someone can teach me how to write a java code on convert hexadecimal to decimal and the decimal to hexadecimal.
which is the code not using following tools:
int i = 29;
String octal = Integer.toOctalString(i);
String hex = Integer.toHexString(i);
String binary = Integer.toBinaryString(i);

thanks

[Stefan Wagner]

How would you convert the decimal 132 to hex by hand/ on paper?
How would you convert a7 to decimal without pc?

[Qing Tian]

on paper that I know
convert 132 to hex is:
132/16 = 8 remainder 4, so the hex will be 84

convert a7 to decimal is:
10(a)* 16 + 7 * 1= 167

I was confused if the number like 24032 and by hand the steps will be:
24032/16=1502 r 0
1502/16 = 93 r 14 (E)
93/16 = 5 r 13 (D)
5/16 = 0 r 5
the hex will be 5DE0
in the java code how the loop divide 16 untill decimal=0 and also the output can display like 5DE0 in order?
(I start learn java on 3 weeks ago so )
did I'm right on calculate? thanks for your help.
[ August 18, 2004: Message edited by: Qing Tian ]

[celine mcgowan]

Hi there!

I was looking into the same problem myself not so long ago! Hard to find the solution, isn't it?!!! Behind the .toHexString etc. all that's happening is:
Convert int to Hex:

 String hex = Integer.toString(i , 16 /* radix */ ); 
// i.e. the number in Base 16 

To go back to int from hex:

 int i = Integer.parseInt(g.trim(), 16 /* radix */ ); 

Similarly to convert from int to Binary String:

 String bin= Integer.toString(i , 2/* radix */ );
//i.e. the number to Base 2 

To go back to int from hex:

 int i = Integer.parseInt(g.trim(), 2/* radix */ ); 

Hope this helps... By the way, i find it easier (less cumbersome) to convert to Binary before converting to Hex. When you get the binary number, you're then just converting every four bits to the Hex equivalent...

Cheers,
Celine

[Hans Achternaam]

Qing, thats the right method to convert from hex to dec.

[Qing Tian]

thank you all for help, that will help me alot!

[Michael Dunn]

Here's a 'manual' way

for args[] enter eg
24032 10 16
or
5DE0 16 10

class Conversions
{
  public static void main(String args[])
  {
    String converted = convert(args[0],Double.parseDouble(args[1]),
                                      Double.parseDouble(args[2]));
    System.out.println(args[0] + " (base "+args[1]+")"+
      " converts to "+converted+ " (base "+args[2]+")");
    System.exit(0);
  }
 
  private static String convert(String oldNum,double base1,double base2)
  {
    long temp=0;
    int x = 0;
    String nextChar;
    String convertedNumber = "";
    String chars = "0123456789ABCDEF";
    for(int i = 0; i < oldNum.length(); i++)
    {
      if(chars.indexOf(oldNum.substring(i,i+1)) >= base1 ||
         chars.indexOf(oldNum.substring(i,i+1)) < 0) return "error - invalid data";
    }
    for(int i = oldNum.length(); i > 0; i--)
    {
      nextChar = oldNum.substring(x,x+1);
      temp += chars.indexOf(nextChar)*Math.pow(base1,i-1);
      x++;
    }
    x=0;
    while(temp > Math.pow(base2,x)) x++;
    int index = 0;
    for(int i=1; i<=x; i++)
    {
      index = (int)(temp/Math.pow(base2,x-i));
      convertedNumber += chars.substring(index,index+1);
      temp-= index*Math.pow(base2,x-i);
    }
    return convertedNumber;
  }
}

[Qing Tian]

thank you Michael that you give me more idea on these codes.