How to add an element to a DoubleLinkedQueue in Dart

The **`dart:collection` library** provides advanced collection support for the Dart language. It also contains the `DoubleLinkedQueue<E>` class which implements the abstract ```Queue<E>``` class using a doubly-linked list.

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## The ```clear()``` method
The ```DoubleLinkedQueue<E>``` class contains the **`clear()` method** which removes all the elements of the queue. The queue size becomes zero after calling the `clear()` method.

>A **queue** is a FIFO (First In First Out) data structure.  In a queue, the element that is added first will be deleted first. 

The `clear()` method modifies the state of the queue. The illustration below shows how the `clear()` method works.

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## Syntax

The prototype of the `clear()` method is shown below.

```
void clear()
```

## Arguments

The `clear()` method does not take any arguments.

## Return values
- The `clear()` method does not return any value.
- The `clear()` method is a constant-time operation.

## Code

The code below shows how the `clear()` method can be used in Dart.


import 'dart:collection'; 
void main() { 
   var quadNations = DoubleLinkedQueue<String>();
   
   quadNations.add("India"); 
   quadNations.add("US"); 
   quadNations.add("Australia");   
   quadNations.add("Japan");   
   print('Printing Queue Elements');
   print(quadNations); 

   quadNations.clear();
   print('Removed all elementes using clear() method');

   print('Printing Queue Elements');
   print(quadNations); 
}  

## Explanation

The code above performs the following actions:

- An instance of the ```DoubleLinkedQueue``` class of type ```String``` is initialized in line 3.

- Next, a few strings, ```"India"```, ```"US"```, ```"Australia"```, and ```"Japan"```,  are added to the queue using the ```add()``` method. 
- The queue elements are displayed as `{India, US, Australia, Japan}`. All the elements are added to the end of the queue, as the queue is a FIFO data structure.
- The ```clear()``` method in line 12 removes all elements of the queue.
- Upon printing all the queue elements again, it can be observed that the queue has become empty and there are no elements in the queue.

What is DoubleLinkedQueue.clear() method in Dart?

DoubleLinkedQueue<E>'s clear() method in Dart removes all elements, resetting the queue size to zero.

What is DoubleLinkedQueue.clear() method in Dart?

The clear() method

Syntax

Arguments

Return values

Code

Explanation

The `clear()` method