Programming :: Equivalence Classes Based On Field Values And Multi-key Hashtable?

I've got a set of objects (all of the same type). I'm trying to think of a good way to divide it into equivalence classes, with equivalence of two objects defined as meaning a specified set of attributes are equal for both objects. More concretely, I've got:

- a Java class with around 50 fields
- a bunch of instances of the class

I want:

- to divide the instances into a few sets
- in each set, each instance has field 1 - field 5 equal to fields 1-5 of the other instances in the set.

The method I've come up with is to generate a hashcode for each instance based on the hashcodes of fields 1-5*, and map the hashcode to one of my sets. Ignoring problems with potential hashcode collisions (which I'm expecting to be too rare to worry about for now), does that sound reasonable? It seems simple enough, but I'm wondering if there's a simpler method I haven't thought of.

* I'll generate the hashcode using a method based on Eclipse's generic hashcode method, which looks like this:

Code:

public int hashCode() {
final int prime = 31;
int result = 1;

[code]....