Difference Between HashMap VS HashSet Java

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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 interfaceIt 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 duplicatedHashSet doesn’t allow duplicate objects
It allows a maximum of one null key but any number of NULL values allowedHashSet allows a maximum of one null object to be added
It internally uses an array of Entry<K, V> objectsHashSet internally uses HashMap to store unique objects
Performance-wise, HashMap is faster than HashSetPerformance-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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