Should we declare it as Queue or Priority Queue while using Priority Queue in Java?


Introduction

The queue is a linear data structure that follows the FIFO approach to insert and extract its data. A priority Queue is a structured Queue, where all data have some priorities for their processing. In Java, a queue or priority queue is an interface.

In this tutorial, we will examine whether we should declare a queue or priority queue as a Priority Queue in Java.

Queue

A Queue in Java is an interface and that interface belongs to java.util package. The queue interface extends the Collection Interface and this interface has several methods.

Queue uses FIFO (First In First Out) approach for its data processing. According to this approach, the data inserted first in the Queue will be first at the terminal point. It has two endpoints: Rear and Front. The rear is used to insert the elements. Queue data are removed from the Front end.

There are two types of Queues in Java: Bounded and Unbounded Queues

  • Bounded queues are defined in the java.util.concurrent package.

  • Unbounded queues are defined in java.util package

There are double-ended queues that provide insertion and deletion of the elements from both ends. There are two classes in the queue interface: Linked List and Priority Queue. We can implement a queue using any of the above.

Syntax of Queue in Java

Queue <queue_name> = new Queue()

Prototype of the Queue

Public interface Queue<E> extends Collection<E>

Priority Queue

In Java, it is a class in the Queue interface and it associates priority with each queue element. It is an ordered queue where Queue data are arranged in a particular order: increasing or decreasing order. It helps Queue in a systematic organization and makes data searching easy and fast.

Syntax of Priority Queue in Java

PriorityQueue<data_type> queue_name = new PriorityQueue<>();

Prototype of the Priority Queue

public class PriorityQueue<E> extends AbstractQueue<E implements Serializable
Here, E is the data type of the Priority Queue.

Should we declare a Queue or Priority Queue as a Priority Queue in Java

The answer to this question depends on the requirement of the Queue. A Priority Queue is useful when the queue data needs to be arranged in a particular order with deletion based on maximum or minimum priority.

  • With Priority Queue, data insertion is complicated compared to the simple Queue in Java, so if you do not want any order with your queue do not define it as Priority Queue. A queue is easy to manage and implement.

  • With Simple Queue, there is a disadvantage of its limited size and it is not effective for easy searching. Priority Queues are not size limited and are organized. So by defining a priority queue as a priority queue in Java your execution speed will increase.

Impact of converting queue or priority queue as a priority queue in Java

  • Queue as a Priority Queue

    You can declare a Queue as a Priority Queue using following syntax:

Queue<data_type> queue_name = new PriorityQueue<>();

For example −

 Queue<int> p = new PriorityQueue<>();

    By using a Queue as a Priority queue it will help in ordering a queue with just a single line declaration. The drawback of this approach is: some of the priority queue functionalities will not work with the queue and this will generate errors in the code.

  • Priority Queue as a Priority Queue

    The syntax to declare a Priority Queue as a Priority Queue in Java is:

PriorityQueue<data_type> queue_name = new PriorityQueue<>();

For example −

 PriorityQueue<int> pq = new PriorityQueue<>();

By using a priority queue as a priority queue the program time complexity will be less with O(1), that means faster searching and working with largest and smallest elements. You can use all its functions. It has a drawback that using deQueue() and enQueue() functions will lead to time complexity of O(log n).

Conclusion

Declaring a queue or a priority queue as a priority queue in Java depends on the requirement, limitations, and benefits. The declaration of the queue as a priority queue will generate errors in the code and limit the functionalities of some of the priority queue methods.

It is advisable to use a priority queue as a priority queue to access all the methods and advantages of a priority queue in Java.

Thank You.

Updated on: 22-Feb-2023

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