Removes an instance of a given element o if it is present in the queue. Removes and returns the head of the queue. Returns the head of the queue without deleting the element. Insert given element e to the PriorityQueue. Method to get an iterator for the given PriorityQueue. Returns a custom comparator used for the ordering of elements in the Queue.Ĭhecks if the PriorityQueue contains the given element o. ("\nPriorityQueue contents:") Ĭlears the PriorityQueue by deleting all the elements. Define the iterator for PriorityQueue and print its elements ("PriorityQueue Head:" cities_queue.element()) initialize the PriorityQueue with values PriorityQueue cities_queue=new PriorityQueue() We create an object of PriorityQueue class, add values to it, and then display the contents of the Queue using Iterator. The below program demonstrates a simple PriorityQueue in Java. The methods that retrieve elements of the Priority Queue have constant time complexity.Priority Queue has linear time complexity for remove as well as contains methods.The time complexity of Priority Queue for insertion(enqueue) and deletion (dequeue) methods, is O(log(n)). The below diagram shows the class hierarchy for the PriorityQueue class. The general declaration of the PriorityQueue class is given below: public class PriorityQueue extends AbstractQueue implements Serializable The PriorityQueue class inherits Java Queue Interface and is a part of the java.util package. Thus if we desire synchronized access, we should use the PriorityBlockingQueue. Priority Queue implementation is not thread-safe.The head or front of the queue contains the least element as per the natural ordering.PriorityQueue inherits from the classes like AbstractQueue, AbstractCollection, Collection, and Object.For non-comparable objects, we cannot create a priority queue.PriorityQueue does not allow null values.Similarly, for an alphabetical priority queue, ASCII values will be considered and the queue elements will be ordered as per the ASCII values.Įnlisted below are some of the major characteristics of the PriorityQueue: Thus when an element is removed from the priority queue shown above, then it will be the least element. In Priority Queue, the front of the queue has the least elements as per the natural ordering and the rear is pointed to the greatest element in the queue.Īn example Priority Queue consisting of numbers is shown below.
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