The poll() method of ConcurrentLinkedQueue is used to remove and return the head of this ConcurrentLinkedQueue. If the ConcurrentLinkedQueue is empty then this method will return null.
Syntax:
public E poll()
Returns: This method remove and returns the head of this ConcurrentLinkedQueue or null if this queue is empty.
Below programs illustrate poll() method of ConcurrentLinkedQueue:
Example 1:
// Java Program Demonstrate poll() // 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);
// apply poll()
int response1 = queue.poll();
// print after applying poll method
System.out.println( "Head: " + response1);
// Displaying the existing ConcurrentLinkedQueue
System.out.println( "Current ConcurrentLinkedQueue: " + queue);
}
} |
Output:
ConcurrentLinkedQueue: [4353, 7824, 78249, 8724] Head: 4353 Current ConcurrentLinkedQueue: [7824, 78249, 8724]
Example 2:
// Java Program Demonstrate poll() // 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);
// apply poll() on queue
String response1 = queue.poll();
// print after applying poll method
System.out.println( "Head: " + response1);
// Displaying the existing ConcurrentLinkedQueue
System.out.println( "Current ConcurrentLinkedQueue: " + queue);
// apply poll() on queue more than one time
queue.poll();
queue.poll();
// Displaying the existing ConcurrentLinkedQueue
System.out.println( "After 2 poll() applied\n"
+ "ConcurrentLinkedQueue: " + queue);
}
} |
Output:
ConcurrentLinkedQueue: [Aman, Amar, Sanjeet, Rabi] Head: Aman Current ConcurrentLinkedQueue: [Amar, Sanjeet, Rabi] After 2 poll() applied ConcurrentLinkedQueue: [Rabi]
Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentLinkedQueue.html#poll–