In this quick article, we will see the difference between HashMap and HashSet which are very popular classes of the Java Collections Framework.
1. Implemented Interface
A HashSet is an implementation of Set interface whereas a HashMap is an implementation of Map interface.
Both HashSet and HashMap follows contract of their respective interfaces. A HashSet class represents a unique set of elements whereas a HashMap class represents mapping of key to values.
3. Implementation Details
HashMap is implemented using a hash table whereas a HashSet is backed by a hash table which is nothing but a HashMap instance.
HashSet allows only distinct elements, whereas a HashMap doesn’t permit duplicate keys but allows duplicate values.
5. Null values
HashSet contains at most one null element whereas a HashMap typically allows null as a key and value except some implementations.
When to use HashSet and HashMap?
HashSet can be used when we need to maintain a collection with no duplicates and HashMap when data is key-value pairs and need fast retrieval of value based on some key.
Thanks for reading.