Queue Vs Arraudeque Java Continue Performance Java

A Deque is a double ended queue. It can be used as a Queue or a Stack

If you've studied your basic Data Structures and Algorithms, then I'm sure you're familiar with the Queue and the Stack data structures.

In Java, there are a few different ways to implement either of these data structures. But what way is the best way to implement them?

What is the best way to implement a Queue in Java?
What is the best way to implement a Stack in Java?

The Deque Interface

The Deque is a "double ended queue." As such, it can be used as either a Queue or a Stack. It provides a consistent API for normal operations to add, remove, or peek at elements from either end of the data structure.

The ArrayDeque class implements the Deque interface

Many times, you will want to use the Deque interface as an ArrayDeque. In fact, the Java API documentation even states that the ArrayDeque class will often times be faster than a Queue or a Stack.

This class is likely to be faster thanStack when used as a stack, and faster thanLinkedList when used as a queue.

https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/util/ArrayDeque.html

                
                  Deque<Integer> deque =                    new                    ArrayDeque<Integer>();                
                                  Code language:                  Java                  (                  java                  )                              

Methods for using a Deque as a Queue

Recall that a Queue is a FIFO data structure, or a First In First Out data structure. As such, the Deque interface provides very easy methods for accessing elements at the beginning of the deque.

Methods that throw an exception when the operation fails

                
                  Deque<Integer> deque =                    new                    ArrayDeque<Integer>(); deque.addFirst(1); deque.getFirst();                    // returns 1 but leaves element in deque                    deque.removeFirst();                    // returns 1 and removes element from deque                                  
                                  Code language:                  Java                  (                  java                  )                              

If any of the above methods fail, the Deque interface will throw an exception. This is similar to the Queue interface from Java.

Methods that return null or false when the operation fails

                
                  Deque<Integer> deque =                    new                    ArrayDeque<Integer>(); deque.offerFirst(1); deque.peekFirst();                    // returns 1 but leaves element in deque                    deque.pollFirst();                    // returns 1 and removes element from deque                                  
                                  Code language:                  Java                  (                  java                  )                              

Methods for using a Deque as a Stack

The Stack data structure is a LIFO structure, or a Last In First Out data structure.

What's nice about the Deque interface is that it doesn't make you memorize a whole new set of operations for accessing elements from the end of the deque, the methods are identical to modifying from the front as they are from the back.

Methods that throw an exception when the operation fails

                
                  Deque<Integer> deque =                    new                    ArrayDeque<Integer>(); deque.addLast(1); deque.getLast();                    // returns 1 but leaves element in deque                    deque.removeLast();                    // returns 1 and removes element from deque                                  
                                  Code language:                  Java                  (                  java                  )                              

Methods that return null or false when the operation fails

                
                  Deque<Integer> deque =                    new                    ArrayDeque<Integer>(); deque.offerLast(1); deque.peekLast();                    // returns 1 but leaves element in deque                    deque.pollLast();                    // returns 1 and removes element from deque                                  
                                  Code language:                  Java                  (                  java                  )                              

Adam Allard

Hi, I'm Adam Allard. I'm a Full Stack Software Engineer for Northrop Grumman creating web applications for the DoD. At this time I'm primarily working with Java and Angular based applications, although I have some years of experience in various languages and frameworks from previous jobs where I dabbled with Python & Django, C# & Xamarin, PHP, and Bootstrap. My hobbies include time with my family, wondering when the Green Bay Packers will win their next Super Bowl, drinking over-priced beer, and of course learning and teaching.

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Source: https://pragmaticways.com/heres-why-you-should-use-deque-instead-of-stack-or-queue/

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