What is the difference between hashset and hashmap?

The main differences between HashSet and HashMap are as follows:

1. HashSet is implemented based on HashMap, essentially acting as a set of keys from the HashMap, where it only stores unique keys without their corresponding values, whereas HashMap stores both keys and values.
2. Storage method: HashSet uses a hash table to store data, determining the position of an element in the hash table by calculating the element’s hash code. On the other hand, HashMap stores key-value pairs in a hash table, determining the position of the key-value pair by calculating the hash code of the key.
3. The order of elements: In a HashSet, the elements do not have a fixed order, meaning that the insertion order may not necessarily match the order in which elements are accessed. Similarly, in a HashMap, the key-value pairs also do not have a fixed order, meaning that the insertion order may not necessarily match the order in which elements are accessed.
4. Element uniqueness: Elements in a HashSet are unique and not allowed to be duplicated. Keys in a HashMap are unique and not allowed to be duplicated, but values can be duplicated.

In general, HashSet is suitable for scenarios where unique elements need to be stored, while HashMap is suitable for scenarios where key-value pairs need to be stored.