The java.util.PriorityQueue.peek() method in Java is used to retrieve or fetch the first element of the Queue or the element present at the head of the Queue. The element retrieved does not get deleted or removed from the Queue.
Syntax:
Priority_Queue.peek()
Parameters: The method does not take any parameters.
Return Value: The method returns the element at the head of the Queue else returns NULL if the Queue is empty.
Below programs illustrate the java.util.PriorityQueue.peek() method:
Program 1:
// Java code to illustrate peek()import java.util.*; public class PriorityQueueDemo { public static void main(String args[]) { // Creating an empty PriorityQueue PriorityQueue<String> queue = new PriorityQueue<String>(); // Use add() method to add elements into the Queue queue.add("Welcome"); queue.add("To"); queue.add("Geeks"); queue.add("For"); queue.add("Geeks"); // Displaying the PriorityQueue System.out.println("Initial PriorityQueue: " + queue); // Fetching the element at the head of the queue System.out.println("The element at the head of the" + " queue is: " + queue.peek()); // Displaying the Queue after the Operation System.out.println("Final PriorityQueue: " + queue); }} |
Output:
Initial PriorityQueue: [For, Geeks, To, Welcome, Geeks] The element at the head of the queue is: For Final PriorityQueue: [For, Geeks, To, Welcome, Geeks]
Program 2:
// Java code to illustrate peek()import java.util.*; public class PriorityQueueDemo { public static void main(String args[]) { // Creating an empty PriorityQueue PriorityQueue<Integer> queue = new PriorityQueue<Integer>(); // Use add() method to add elements into the Queue queue.add(10); queue.add(15); queue.add(30); queue.add(20); queue.add(5); // Displaying the PriorityQueue System.out.println("Initial PriorityQueue: " + queue); // Fetching the element at the head of the queue System.out.println("The element at the head of the" + " queue is: " + queue.peek()); // Displaying the Queue after the Operation System.out.println("Final PriorityQueue: " + queue); }} |
Output:
Initial PriorityQueue: [5, 10, 30, 20, 15] The element at the head of the queue is: 5 Final PriorityQueue: [5, 10, 30, 20, 15]