Generating unique hascodes based on arrays

Question

Hi, I have a problem that I'm looking to solve but perhaps I'm getting it more complicated than really is.
So, I have an object (BlaBla) that contains an array of bytes. BlaBla objects are stored in a hashtable. So, I need that the hashtable returns an object when they have the same array content (if they are in the same order).
For example, two BlaBlas with the following arrays:
[2, 3]
[3, 2]are different, but the following BlaBlas are supposed to be treated as the same:
[0,0,0,3]
[0,0,0,3]Basically, I want to count the occurences of the same sequences of bytes of BlaBlas in my Hashtable<BlaBla, Integer>.
My approach is trying to write a hashCode() for BlaBla that returns an unique code for each different array but the same code for equal arrays, but with no success.
Would you, Java gurus :P, suggest a more efficient approach ?
Thanks you.
Edited by: crp on Jan 26, 2009 6:32 PM

Answer 1

crp wrote:
My approach is trying to write a hashCode() for BlaBla that returns an unique code for each different array That's only possible if the number of possible arrays is <= 2^32.
If your array will always hold exactly one int, then the hashcode is the int.
If your array can hold one or two ints, but you constrain each int to only 2^16 possible values, then you can put one int in the high order two bytes, and the other in the low order two bytes.
And so on. If you know enough about your possible values, it may be possible to set up your hashcode to be unique, but it can very easily become impractical.
Hashcodes are not intended to be unique.