The peek() method of ConcurrentLinkedQueue is used to return the head of the ConcurrentLinkedQueue. It retrieves but does not remove, the head of this ConcurrentLinkedQueue. If the ConcurrentLinkedQueue is empty then this method returns null.
Syntax:
public E peek()
Returns: This method returns the head of this ConcurrentLinkedQueue without removing it.
Below programs illustrate peek() method of ConcurrentLinkedQueue:
Example 1:
// Java Program Demonstrate peek()// method of ConcurrentLinkedQueue import java.util.concurrent.*; public class GFG { public static void main(String[] args) { // create an ConcurrentLinkedQueue ConcurrentLinkedQueue<Integer> queue = new ConcurrentLinkedQueue<Integer>(); // Add Numbers to queue queue.add(4353); queue.add(7824); queue.add(78249); queue.add(8724); // Displaying the existing ConcurrentLinkedQueue System.out.println("ConcurrentLinkedQueue: " + queue); // find peek int response1 = queue.peek(); // print after applying peek method System.out.println("Head: " + response1); // Verifying that the head is not removed System.out.println("ConcurrentLinkedQueue after peek: " + queue); }} |
Output:
ConcurrentLinkedQueue: [4353, 7824, 78249, 8724] Head: 4353 ConcurrentLinkedQueue after peek: [4353, 7824, 78249, 8724]
Example 2:
// Java Program Demonstrate peek()// method of ConcurrentLinkedQueue import java.util.concurrent.*; public class GFG { public static void main(String[] args) { // create an ConcurrentLinkedQueue ConcurrentLinkedQueue<String> queue = new ConcurrentLinkedQueue<String>(); // Add String to queue queue.add("Aman"); queue.add("Amar"); queue.add("Sanjeet"); queue.add("Rabi"); // Displaying the existing ConcurrentLinkedQueue System.out.println("ConcurrentLinkedQueue: " + queue); // find peek of queue String response1 = queue.peek(); // print after applying peek method System.out.println("Head: " + response1); // Verifying that the head is not removed System.out.println("ConcurrentLinkedQueue after peek: " + queue); // remove some elements queue.poll(); queue.poll(); // Displaying the existing ConcurrentLinkedQueue System.out.println("Updated ConcurrentLinkedQueue: " + queue); // find peek of queue String response2 = queue.peek(); // print after applying peek method System.out.println("Head: " + response1); // Verifying that the head is not removed System.out.println("ConcurrentLinkedQueue after peek: " + queue); }} |
Output:
ConcurrentLinkedQueue: [Aman, Amar, Sanjeet, Rabi] Head: Aman ConcurrentLinkedQueue after peek: [Aman, Amar, Sanjeet, Rabi] Updated ConcurrentLinkedQueue: [Sanjeet, Rabi] Head: Aman ConcurrentLinkedQueue after peek: [Sanjeet, Rabi]
Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentLinkedQueue.html#peek–
