What does "hash map" mean in programming?

hash map is one of the most common terms in software development. This guide explains what it means, how it is used in practice, and why it matters, with real examples from the developer world.

Definition

A data structure that maps keys to values using a hash function for O(1) average lookup. HashMap is the class name in Java; other languages call the same concept a dictionary, map, or associative array.

Example

"HashMap<String, Integer> wordCount = new HashMap<>(); // Java hash map"

Related terms

hash table
dictionary
hash
map
hash set

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