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Asked: 2026-06-17T08:09:20+00:00

I have this. private ArrayList<String> words; It’s a dictionary, so the words are already

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I have this.

private ArrayList<String> words;

It’s a dictionary, so the words are already sorted. By old study I know that a binomial search should be really very very quick, I suppose that Java already implements what is necessary.

So, what is the most efficient way of finding if a certain string exists inside a sorted ArrayList ?
Or should I use a different type?

Thank you.

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  1. Editorial Team

    Or should I use a different type?

    Try using a HashSet<String> instead. Its contains method has O(1) lookup assuming that there are not too many hash collisions. From the documentation:

    This class offers constant time performance for the basic operations (add, remove, contains and size), assuming the hash function disperses the elements properly among the buckets.

    A binary search on a sorted ArrayList is only O(log n). This is still very fast, but it is not as fast as using a HashSet.

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