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

#    
## The containsAll() method
The `HashSet<E>` class contains the **`containsAll()` method**, which is used to check if the `HashSet` contains all the elements of the specified input collection.

> Note: The **`HashSet<E>`** is a collection of unique elements and provides constant-time `add`, `remove`, and `contains` operations. The `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 `containsAll()` method works:




## Syntax
The syntax of the `containsAll()` method is as follows:
```dart
bool containsAll(Iterable<Object?> other)
```
## Parameters
The `containsAll()` method takes a collection of objects as input and checks if the `HashSet` contains all the elements of the input collection.

## Return value
This method returns `True` if the `HashSet` contains all the elements of the input collection. Otherwise, it returns `False`.

## Code
The code given below shows us how the `containsAll()` method works in Dart:


import 'dart:collection'; 
void main() { 
  var sportsList = HashSet<String>();
  
  sportsList.add("Cricket"); 
  sportsList.add("Football"); 
  sportsList.add("Hockey");
  sportsList.add("Volleyball");
  print('HashSet : $sportsList'); 

  List<String> otherList = ["Hockey","Football"];
  print('List : $otherList'); 

  var result = sportsList.containsAll(otherList);
  print('Does HashSet contains all elements of List?: $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 sports to the ashset: `"Cricket"`, `"Football"`, `"Hockey"`, and `"Volleyball"`.
- Line 11: We create an input list and add `"Hockey"` and `"Football"` to it.
- Line 14: We call the `containsAll()` method and pass the list that was created above as input. It returns `True`, as all the list elements are present in the Hashset.

- We use the `print()` function of the core library to display the set elements and the result of the `containsAll()` method.

What is HashSet.containsAll() in Dart?

The containsAll() method

Syntax

Parameters

Return value

Code

Explanation