{"id":665,"date":"2021-01-16T19:00:44","date_gmt":"2021-01-16T19:00:44","guid":{"rendered":"https:\/\/pragmaticways.com\/?p=665"},"modified":"2021-02-26T19:24:30","modified_gmt":"2021-02-26T19:24:30","slug":"heres-why-you-should-use-deque-instead-of-stack-or-queue","status":"publish","type":"post","link":"https:\/\/pragmaticways.com\/heres-why-you-should-use-deque-instead-of-stack-or-queue\/","title":{"rendered":"Here’s why you should use Deque instead of Stack or Queue"},"content":{"rendered":"\n
\"why
A Deque is a double ended queue<\/em>. It can be used as a Queue or<\/em> a Stack<\/figcaption><\/figure>\n\n\n\n

If you’ve studied your basic Data Structures<\/a> and Algorithms, then I’m sure you’re familiar with the Queue<\/strong> and the Stack<\/strong> data structures. <\/p>\n\n\n\n

In Java, there are a few different ways to implement either of these data structures. But what way is the best<\/em> way to implement them?<\/p>\n\n\n\n

What is the best way to implement a Queue in Java?
What is the best way to implement a Stack in Java?<\/p>\n\n\n\n\n\n

The Deque Interface<\/h2>\n\n\n\n

The Deque is a “double ended queue.” As such, it can be used as either a Queue or<\/em> a Stack. It provides a consistent API<\/strong> for normal operations to add, remove, or peek at elements from either end of the data structure. <\/p>\n\n\n\n

\"the<\/figure>\n\n\n\n

The ArrayDeque class implements the Deque interface<\/h2>\n\n\n\n

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

This class is likely to be faster than Stack<\/code><\/a> when used as a stack, and faster than LinkedList<\/code><\/a> when used as a queue.<\/p>https:\/\/docs.oracle.com\/en\/java\/javase\/15\/docs\/api\/java.base\/java\/util\/ArrayDeque.html<\/a><\/cite><\/blockquote>\n\n\n

Deque<Integer> deque = new<\/span> ArrayDeque<Integer>();<\/code><\/div>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
Methods for using a Deque as a Queue<\/h3>\n\n\n\n
Recall that a Queue<\/strong> is a FIFO<\/strong> data structure, or a First In First Out<\/em> data structure. As such, the Deque interface provides very easy methods for accessing elements at the beginning of the deque. <\/p>\n\n\n\n
Methods that throw an exception when the operation fails<\/h4>\n\n\n
Deque<Integer> deque = new<\/span> ArrayDeque<Integer>();\ndeque.addFirst(1<\/span>);\ndeque.getFirst(); \/\/ returns 1 but leaves element in deque<\/span>\ndeque.removeFirst(); \/\/ returns 1 and removes element from deque<\/span><\/code><\/div>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
Methods that return null or false when the operation fails<\/h4>\n\n\n
Deque<Integer> deque = new<\/span> ArrayDeque<Integer>();\ndeque.offerFirst(1<\/span>);\ndeque.peekFirst(); \/\/ returns 1 but leaves element in deque<\/span>\ndeque.pollFirst(); \/\/ returns 1 and removes element from deque<\/span><\/code><\/div>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
Methods for using a Deque as a Stack<\/h3>\n\n\n\n
The  Stack<\/strong> data structure is a LIFO<\/strong> structure, or a Last In First Out<\/em> data structure. <\/p>\n\n\n\n
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 <\/em>of the deque, the methods are identical to modifying from the front as they are from the back. <\/p>\n\n\n\n
Methods that throw an exception when the operation fails<\/h4>\n\n\n
Deque<Integer> deque = new<\/span> ArrayDeque<Integer>();\ndeque.addLast(1<\/span>);\ndeque.getLast(); \/\/ returns 1 but leaves element in deque<\/span>\ndeque.removeLast(); \/\/ returns 1 and removes element from deque<\/span><\/code><\/div>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>\n\n\n
Methods that return null or false when the operation fails<\/h4>\n\n\n
Deque<Integer> deque = new<\/span> ArrayDeque<Integer>();\ndeque.offerLast(1<\/span>);\ndeque.peekLast(); \/\/ returns 1 but leaves element in deque<\/span>\ndeque.pollLast(); \/\/ returns 1 and removes element from deque<\/span><\/code><\/div>Code language:<\/span> Java<\/span> (<\/span>java<\/span>)<\/span><\/small><\/pre>","protected":false},"excerpt":{"rendered":"
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<\/p>\n","protected":false},"author":1,"featured_media":675,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[31],"tags":[43,44,46,45],"_links":{"self":[{"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/posts\/665"}],"collection":[{"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/comments?post=665"}],"version-history":[{"count":0,"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/posts\/665\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/media\/675"}],"wp:attachment":[{"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/media?parent=665"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/categories?post=665"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pragmaticways.com\/wp-json\/wp\/v2\/tags?post=665"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
If any of the above methods fail, the Deque interface will throw an exception. This is similar to the Queue interface<\/a> from Java. <\/p>\n\n\n\n