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Asked: 2026-06-16T03:00:24+00:00

I want to create a HashMap with RGB colors as keys. How should I

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I want to create a HashMap with RGB colors as keys. How should I store them to have best performance?
I mean, how does the “speed” of a hashmap refer to the object type of the key?

Should I use Integer (018052175) where each triplet would be one of RGB, String (1234AF) as HEX, or own Color class with int r, g, b? What might be the fastest implementation?

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1 Answer

  1. Editorial Team

    The speed of hash map is constrained by several essential properties of the hashCode and equals functions:

    • How easy it is to calculate,
    • How well is hashCode at distributing values into buckets, and
    • How easy it is to compare values for equality

    The hashCode function of a String is very good, and String caches its result to improve performance. However, equality check may be longer than with Integer.

    The Integer class has a very hard-to-beat implementation of hashCode in terms of speed, but since the hash codes of similar colors would be close to each other, you may get more collisions with Integers.

    Color is as fast as the Integer, but it is also the most descriptive. I seriously doubt that choosing one of these three representations would hamper performance so significantly as to make a visible difference, so I would suggest going for the most descriptive choice, and then profile if necessary.

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