Data Structures - Queue
For this discussion, I choose to write about the queue data structure. A queue stores one or more items where we are only allowed to insert an item on one end of the list and remove an item on another end. The queue does not allow us to freely modify the structure or arrangement of items in the container. It is up to the queue on how it will organize itself and which items will be the next to be removed.
Types of Queues in Java
Java provides different kinds of queues. They all carry the same concept but they differ on the strategy on how they are made and the order of arrangement thus the queue is an interface with many implementing sub-interfaces, abstract classes, and concrete classes. This discussion is going to be very long if I will write each and every one of them so I will focus on the core concept of the queue and tackle the common queue implementations.
Java implements a queue using a dynamic array or a linked list. When using a queue, we are not free to tell whether to use the array or linked list version. For instance, a basic queue uses a linked list while a deque (a sub-interface of a queue) uses an array. Dynamic arrays and linked lists as we know have its advantages and dis-advantages depending on the situation. It was up to the developer to decide whether to use an array or linked list and we could just safely assume that they decided to use them because it would be the most efficient and effective way to process items and use available resources like proper utilization of memory and processing speed.
FIFO(First-In-First-Out) Queue
The most common queue that we know would be the First-In-First-Out (FIFO) queue. From the term itself, whichever item we insert first in the queue would be the first to get out and whichever item we insert last would be the last to get out. There are also other implementations of a queue called a priority queue which gives priority to items that are inserted. In a priority queue, a certain criteria is going to be used to know which item will be retrieved next so it follows a different order from the FIFO queue. There’s also what we call a deque (double ended queue) where it extends the feature of a queue allowing it to insert and remove items on both ends.
Given the different kinds of queue that Java provides we choose what fits most to use in our project. Though it is possible to simulate the operations of a queue using other provided data structures like Array List and Linked List, we cannot guarantee if our version is more efficient than what is already provided. If we do that then we are competing with people who built Java themselves. The only valid reason to rebuild or extend a queue is if there are missing features in our project that the Java queue cannot provide. Using Linked List and Array List as an alternative to a queue is also not fitting because they have many operations that contradict the concept of a queue and these operations are not built to optimize FIFO, Priority Based ordering, and similar operations.
A queue is an important data structure and will not go away. There will always be time that we need to put order on things and a queue will always be there as an option. It is a handy data structure that we can always look upon as part of our project if needed.