Converting Hex to decimal - with a twist

[Toby Freeman]

Hi All

I'm having a bit of an issue trying to convert a String hexidecimal value to a decimal.

The data I'm receiving are cartesian coordinates (X,Y,Z) as Strings in a hexadecimal format of a fixed length i.e. "003df860".

Normally, I would just use the following code:

Integer.parseInt(x_hex,16)

to return my answer. This works fine for positive coordinates.

However, cartesian coordinates can be also be negative, so with a value such as "FFFB6825", I want parseInt to return -301019, not a NumberFormatException as the the number is too large (4294666270).

Anyone got any suggestions as to how I can get round this?

Is it one of those things that is staring at me right under my nose?

Thanks

Toby

[Stan James]

I'm thinking if it starts with F then XOR the string, do the parserInt() bit, flip the sign and subtract 1.

XOR the string is interesting ... gotta translate F=0 E=1, D=2 ... 0=F. This is real ugly but seems to work:

  
public class Bogus
{
   public static void main(String[] args)
   {
      String input = "FFFB6825";
      char[] c = new char[] { '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
      char[] i = new char[8];
      char[] o = new char[8];
      input.getChars(0,8,i,0);
      for(int p = 0; p < 8; p++)
      {
          int q = i[p]-'0';
          if(q>9) q-=7;
          System.out.println(i[p] + " " + q);
          o[p] = c[15-q];
      }
      String s = new String(o);
      System.out.println(s);
      int r = -1 - Integer.parseInt(s,16);
      System.out.println(r);
   }
}

[Dirk Schreckmann]

You might prefer to simple first make a long, then cast the value to int.

public class Foo
{
  public static void main(String[] args)
  {
    String hex = "FFFB6825";
    long longValue = Long.parseLong(hex, 16);
    System.out.println(longValue);
    int intValue = (int)longValue;
    System.out.println(intValue);
  }
}

[Dirk Schreckmann]

Oh, and...

Welcome to JavaRanch, Toby Freeman!

[Toby Freeman]

Dirk - fantastic thank you.

I'm coming here again if I keep getting answers so quick...

Toby

[Stan James]

Ah, does that cast to int convert from a very large positive long to a negative int? I tried long and saw the wrong number but never tried casting it back.