8 Difference between HashMap and HashSet in Java | Examples
Hello readers,
In the previous tutorials we have learnt about the different classes in Java Collections namely,
- ArrayList – an implementation of List interface
- HashSet – an implementation of the Set interface and
- HashMap – an implementation of the Map interface.
Let us compare a them in Java.
Similarities between Hashset and HashMap
Apart from the word ‘hash’, both the classes have few similarities, specifically –
- Both of them are a hash-based collection in Java.
- Both are them are not synchronized.
- None of them provide an assurance for the order of insertion of elements.
Now let us check out the points of difference between a HashMap and a HashSet.
Difference between Hashmap and Hashset in Java
HashMap v/s HashSet in tabular form
| Basis of Difference | HashMap | HashSet |
|---|---|---|
| Definition | HashMap is an implementation of the Map interface. | HashSet is an implementation of the Set interface. |
| Duplicates | It does not allow duplicate keys however it allows duplicate values to be stored. | It does not allow duplicate values. In case the user enters a duplicate value, then the value is overridden. |
| Storage | Values in HashMap are stored in the form of key and value pairs with the help of hashing technique. | A HashMap internally to store it’s objects, i.e. every time a HashMap object is also created with the HashSet object. |
| Null Values | It consists of multiple null values but just a single null key. | It allows only one single null value. |
| Insertion of elements | Insertion of elements into HashMap is done with the help of put(Object key, Object value) method. | Insertion of elements into HashSet is done with the help of add(Object e) method. |
| Performance | HashMap is faster than HashSet as the every value is associated to a unique key. | HashSet is comparatively slower than HashMap as the member object used for calculating hashcode value can be similar for two objects. |
| Usage (when to use) | It is preferred in case uniqueness of elements is not required. | It is preferred in case uniqueness of elements is required. |
| Example | {1=A, 2=E, 3=O}. – Here A,E,O are values and 1,2,3 are the respective keys. | [A, E, U, I, O] – It a set and A,E,I,O,U are the elements in set. |
And that’s it. These are the key differences between a HashMap and HashSet.
To learn the syntax for creating these classes, check the tutorial link shared above.
If you have any questions or if you want to discuss any point, let me know your thought by commenting below.
Happy Learning!
