HashCode

This question scares me! It shows a complete lack of mathematical knowledge!

If you have an N character unicode string then there are 65536^N possible combinations so to be unique you need a number between 0 and 65536^N!

Even if your string only contains ASCII you will still need 0 to 128^N.

You say that your string is long so if I assume 100 characters then you need 0 to 128^100. A VERY VERY VERY ... big range.

MD5 and SHA1 are ways to get a probably unique number but they don't garantee unique.

Roger

sabre150a at 2007-7-15 13:31:57 >

Im sure you could get away with using half that number if you only

want unicode 16 values (no four byte extensions). you can pack two chars

into an int. 4 chars if you are restricted to 8 bit chars.

Then you only need 4294967296 bytes to represent each string uniquely.

look I just saved 4Gig. 7Gig if you use the ASCII approach :P

matfud

duftama at 2007-7-15 13:31:57 >

> I just have a long string and i want to make a integer

> of fixed length from that string, i thought of using

> hashcode() method to get the integer, but the hashcode

> will not be unique, can one tell me how can i convert

> the string to UNIQUE FIXED LENGTH INTEGER.

>

> Thaning you

> M. Muthu

public class UniqueStringToIntGenerator {

private Vector vec = new Vector();

public int getIntFromString(String s) {

for (int i = 0; i < vec.size(); i++) {

if (vec.get(i).equals(s))

return i;

}

vec.add(s);

return vec.size() - 1;

}

}

P.S. This is meant to be a joke.

rkippena at 2007-7-15 13:31:57 >