Hashmap vs Hashset Difference In Java [ Updated in 2023 ]

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HashMap VS HashSet Java: In this article, we will discuss the difference between HashMap and HashSet Java classes in detail i.e.; HashMap VS HashSet Java.

HashMap VS HashSet Java

HashMap	HashSet
It implements Map interface	It implements Set interface
Used to store key-value pairs using put method example: hm.put(key, value);	Used to store only unique objects using add method example: hs.add(object);
It doesn’t allow duplicate keys but values can be duplicated	HashSet doesn’t allow duplicate objects
It allows a maximum of one null key but any number of NULL values allowed	HashSet allows a maximum of one null object to be added
It internally uses an array of Entry<K, V> objects	HashSet internally uses HashMap to store unique objects
Performance-wise, HashMap is faster than HashSet	Performance-wise, HashSet is slower than HashMap

When to use HashMap?

It stores key-value pairs which use a hashing technique to store key-value pairs where methods are NOT synchronized
So, the search operation is faster with multiple threads access
So, if a business requirement is to store key-value pairs for faster search operation or number of search operation on the basis of keys; without concerning concurrent access to the map
Then, HashMap is the very apt choice

When to use HashSet?

HashSet stores unique elements using the hashing technique
So, the search operation is faster
So, if the business requirement is to store unique elements for faster search operation or more number of search operation without concerning insertion order
Then, HashSet is the very apt choice

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