java hashset api

A HashSet is a class in the Java Collections Framework that implements the Set interface and stores a collection of unique elements. It uses a hash table to store the elements, which allows for fast lookups and insertions.

Here is an example of how to create a HashSet in Java:

HashSet<String> set = new HashSet<>();

In this example, the set variable is a HashSet object that stores strings. The HashSet class has a single generic type parameter: the type of the elements (String in this case).

You can add elements to the HashSet using the add method.

For example:

set.add("apple");
set.add("banana");
set.add("orange");

To check if an element is in the HashSet, you can use the contains method and specify the element.

For example:

if (set.contains("apple")) {
    // the element "apple" is in the set
}

You can use the size method of the HashSet class to get the number of elements in the set.

For example:

int size = set.size(); // returns 3

You can use the isEmpty method of the HashSet class to check if the set is empty.

For example:

if (set.isEmpty()) {
    // the set is empty
}

You can use the clear method of the HashSet class to remove all the elements from the set.

For example:

set.clear(); // removes all the elements from the set

You can use the iterator method of the HashSet class to get an iterator over the elements in the set.