# 
## Overview
The `dart:collection` library provides advanced collection support for the Dart language. The library contains the **`HashSet<E>` class**, which is an unordered hash-table-based implementation of the abstract `Set<E>` class.

## The `intersection()` method

The `HashSet<E>` class provides the  **`intersection()` method**. The method takes a set as input and returns a new set, which has all the elements of the hash set. These elements are also present in the input set.


>**Note**: **`HashSet<E>`** is a collection of unique elements that provides constant-time `add`, `remove`, and `contains` operations. `HashSet<E>` does not have a specified iteration order. However, multiple iterations on the set produce the same element order.

The figure below illustrates how the `intersection()` method works.


## Syntax
The syntax of the `intersection()` method is as follows:
```
Set<E> intersection(Set<Object?> other) 
```
## Parameters
The `intersection()` method takes a set as input.

## Return value
The `intersection()` method returns a new set containing the intersection of the HashSet and the input set.

## Code
The code below shows how the `intersection()` method works in Dart.


import 'dart:collection'; 
void main() { 
   var countrySet = HashSet<String>(); 
     
   countrySet.add("USA"); 
   countrySet.add("Japan"); 
   countrySet.add("India");
   countrySet.add("UAE");
   
   print('Printing First  Elements');
   print(countrySet); 

   var otherCountrySet = HashSet<String>();
   otherCountrySet.add("USA"); 
   otherCountrySet.add("Germany"); 
   otherCountrySet.add("France");

  print('Printing Other Set Elements');
  print(otherCountrySet);
  var result = countrySet.intersection(otherCountrySet);
  
  print('Printing Intersection Set Elements');
  print(result); 
   
}  

## Explanation
* **Line 3**: We create an instance of a `HashSet` class of type `String`.

* **Lines 5–8**: We use the `add()` method to add a few country names to the `HashSet`: `"USA"`, `"Japan"`, `"India"`, and `"UAE"`.

* **Lines 13–16**: We create another instance of a `HashSet` and add a few country names to it.

* **Line 20**: We call the `intersection()` method on the first `HashSet` passing the second `HashSet` as input.

* **Line 23**: We use the `print()` function of the core library to display the result of the `intersection()` method.

 What is the HashSet.intersection() method in Dart?

The `HashSet.intersection()` method in Dart returns a new set containing elements found in both the original and the input set.

What is the HashSet.intersection() method in Dart?

Overview

The intersection() method

Syntax

Parameters

Return value

Code

Explanation

The `intersection()` method