The PriorityQueue interface in Java represents a priority queue based on the heap data structure. Unlike a regular queue, where elements are retrieved in a first-in-first-out (FIFO) manner, a priority queue retrieves elements based on their priority. The element with the highest priority is dequeued first. In Java, PriorityQueue is implemented as a priority heap, which is a binary heap where elements are ordered either by their natural ordering or by a comparator provided at the time of queue creation.
import java.util.PriorityQueue;
// Syntax for creating a PriorityQueue with natural ordering
PriorityQueue<Type> queueName = new PriorityQueue<>();Code language: JavaScript (javascript)Methods:
- Adding Elements:
- boolean offer(element): Inserts the specified element into the priority queue.
- void add(element): Inserts the specified element into the priority queue.
   2. Removing Elements:
- element poll(): Retrieves and removes the head of the queue (element with the highest priority).
- element remove(): Retrieves and removes the head of the queue.
- element peek(): Retrieves, but does not remove, the head of the queue.
- element element(): Retrieves, but does not remove, the head of the queue.
   3.Checking Size and Empty Status
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- int size(): Returns the number of elements in the priority queue.
- boolean isEmpty(): Returns true if the priority queue contains no elements.
import java.util.PriorityQueue;
public class PriorityQueueExample {
public static void main(String[] args) {
// Creating a PriorityQueue to store task priorities
PriorityQueue<Integer> taskQueue = new PriorityQueue<>();
// Adding task priorities to the PriorityQueue
taskQueue.add(5); // low priority task
taskQueue.add(1); // highest priority task
taskQueue.add(3); // medium priority task
taskQueue.add(2); // high priority task
taskQueue.add(4); // medium priority task
// Displaying the priority queue
System.out.println("PriorityQueue of tasks:");
while (!taskQueue.isEmpty()) {
System.out.println(taskQueue.poll());
}
// Checking if the priority queue is empty
System.out.println("Is the priority queue empty? " + taskQueue.isEmpty());
}
}D:\>javac PriorityQueueExample.java
D:\>java PriorityQueueExample
PriorityQueue of tasks:
1
2
3
4
5
Is the priority queue empty? trueCode language: PHP (php)PriorityQueue in Java provides a powerful tool for managing elements based on their priority levels. It ensures efficient access to the highest-priority elements and supports both natural and custom ordering criteria. Understanding how to use PriorityQueue enables developers to design efficient algorithms for priority-based processing in various applications, from task scheduling to event handling.