The java.util.PriorityQueue.comparator() method shares an important function of setting and returning the comparator that can be used to order the elements in a PriorityQueue. The method returns a null value if the queue follows the natural ordering pattern of the elements.
Syntax:
comp_set = (PriorityQueue)Priority_Queue.comparator()
Parameters: The method does not take any parameters.
Return Value: The method returns the comparator used to order the elements of the queue in a specific order. It returns a Null value if the queue follows the default or natural ordering pattern.
Below programs illustrate the java.util.PriorityQueue.comparator() method:
Program 1: When using natural ordering of the elements:
Java
// Java code to illustrate comparator()import java.util.*;public class Priority_Queue_Demo { public static void main(String[] args) { // Creating an empty Priority_Queue PriorityQueue<Integer> queue = new PriorityQueue<Integer>(); // Adding elements to the queue queue.add(20); queue.add(24); queue.add(30); queue.add(35); queue.add(45); queue.add(50); System.out.println("Priority queue values are: " + queue); // Creating a comparator Comparator comp = queue.comparator(); // Displaying the comparator values System.out.println("Since the Comparator value is: " + comp); System.out.println("it follows natural ordering"); }} |
Output:
Priority queue values are: [20, 24, 30, 35, 45, 50] Since the Comparator value is: null it follows natural ordering
Program 2: When using a specific comparator.
Java
// Java code to illustrate the use of comparator()import java.util.Comparator;import java.util.PriorityQueue;class The_Comparator implements Comparator<String> { public int compare(String str1, String str2) { String first_Str; String second_Str; first_Str = str1; second_Str = str2; return second_Str.compareTo(first_Str); }}public class Priority_Queue_Demo { public static void main(String[] args) { PriorityQueue<String> queue = new PriorityQueue<String>(new The_Comparator()); queue.add("G"); queue.add("E"); queue.add("E"); queue.add("K"); queue.add("S"); queue.add("4"); System.out.println("The elements with the highest priority element at front of queue" + "order:"); while(!queue.isEmpty()){ System.out.print(" "+queue.poll()); } }} |
Output
The elements with the highest priority element at front of queueorder: S K G E E 4
