Is map mutable in Java?

Mutable maps supports modification operations such as add, remove, and clear on it . Unmodifiable Maps are “read-only” wrappers over other maps. They do not support add, remove, and clear operations, but we can modify their underlying map.

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What is map interface?

The Map interface includes methods for basic operations (such as put , get , remove , containsKey , containsValue , size , and empty ), bulk operations (such as putAll and clear ), and collection views (such as keySet , entrySet , and values ).

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Why is HashMap containsKey O 1?

This implementation provides constant-time performance for the basic operations (get and put), assuming the hash function disperses the elements properly among the buckets. Since containsKey() is just a get() that throws away the retrieved value , it’s O(1) (assuming the hash function works properly, again).

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