hash-code-uniqueness

I have a HashMap with coordinates as keys. Coordinates have 3 longs holding the x, y and z coordinate. (Coordinate is and needs to be a custom class, the coordinates need to be longs). Now i want to be able to access e.g. the field [5, 10, 4] by doing: hashMap.get(new Coordinate(5, 10, 4)) . I have implemented the equals method but that is not enough since apparently i need to provide an implementation for hashCode as well. So my question is how do i generate an unique hashCode from three longs? . Additional: Using a hash generator from an external library is not option. Joshua Bloch tells you

I have a pretty complex object and I need to get uniqueness of these objects. One solution can be done by overriding GetHashCode() . I have implemented a code noted below: public override int GetHashCode() { return this._complexObject1.GetHashCode() ^ this._complexObject2.GetHashCode() ^ this._complexObject3.GetHashCode() ^ this._complexObject4.GetHashCode() ^ this._complexObject5.GetHashCode() ^ this._complexObject6.GetHashCode() ^ this._complexObject7.GetHashCode() ^ this._complexObject8.GetHashCode(); } These complex objects also overrides GetHashCode() and does similar operations . My

I have a system that requires a unique 6-digit code to represent an object, and I'm trying to think of a good algorithm for generating them. Here are the pre-reqs: I'm using a base-20 system (no caps, numbers, vowels, or l to prevent confusion and naughty words) The base-20 allows 64 million combinations I'll be inserting potentially 5-10 thousand entries at once, so in theory I'd use bulk inserts, which means using a unique key probably won't be efficient or pretty (especially if there starts being lots of collisions) It's not out of the question to fill up 10% of the combinations so there's

I want to know the probability of getting duplicate values when calling the GetHashCode() method on string instances. For instance, according to this blog post, blair and brainlessness have the same hashcode (1758039503) on an x86 machine. Large. (Sorry Jon!) The probability of getting a hash collision among short strings is extremely large . Given a set of only ten thousand distinct short strings drawn from common words, the probability of there being at least one collision in the set is approximately 1%. If you have eighty thousand strings, the probability of there being at least one