Queue poll() method in Java
The poll() method of Queue Interface returns and removes the element at the front end of the container. It deletes the element in the container. The method does not throws an exception when the Queue is empty, it returns null instead.
Syntax:
E poll()
Returns: This method returns the element at the front of the container or the head of the Queue. It returns null when the Queue is empty.
Below programs illustrate poll() method of Queue:
Program 1: With the help of LinkedList.
import java.util.*;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
Queue<Integer> Q
= new LinkedList<Integer>();
Q.add( 7855642 );
Q.add( 35658786 );
Q.add( 5278367 );
Q.add( 74381793 );
System.out.println( "Queue: " + Q);
System.out.println( "Queue's head: " + Q.poll());
System.out.println( "Queue's head: " + Q.poll());
}
}
|
Output:
Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786
Program 2: To Demonstrate poll() method of Queue when the Queue becomes empty
import java.util.*;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
Queue<Integer> Q
= new LinkedList<Integer>();
Q.add( 423 );
Q.add( 3432 );
System.out.println( "Queue: " + Q);
System.out.println( "Queue's head: " + Q.poll());
System.out.println( "Queue's head: " + Q.poll());
System.out.println( "Queue: " + Q);
System.out.println( "Queue's head: " + Q.poll());
}
}
|
Output:
Queue: [423, 3432]
Queue's head: 423
Queue's head: 3432
Queue: []
Queue's head: null
Program 3: With the help of ArrayDeque.
import java.util.*;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
Queue<Integer> Q
= new ArrayDeque<Integer>();
Q.add( 7855642 );
Q.add( 35658786 );
Q.add( 5278367 );
Q.add( 74381793 );
System.out.println( "Queue: " + Q);
System.out.println( "Queue's head: " + Q.poll());
System.out.println( "Queue's head: " + Q.poll());
}
}
|
Output:
Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786
Program 4: With the help of ConcurrentLinkedDeque.
import java.util.*;
import java.util.concurrent.ConcurrentLinkedDeque;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
Queue<Integer> Q
= new ConcurrentLinkedDeque<Integer>();
Q.add( 7855642 );
Q.add( 35658786 );
Q.add( 5278367 );
Q.add( 74381793 );
System.out.println( "Queue: " + Q);
System.out.println( "Queue's head: " + Q.poll());
System.out.println( "Queue's head: " + Q.poll());
}
}
|
Output:
Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786
Program 5: With the help of LinkedBlockingDeque.
import java.util.*;
import java.util.concurrent.LinkedBlockingDeque;
public class GFG {
public static void main(String[] args)
throws IllegalStateException
{
Queue<Integer> Q
= new LinkedBlockingDeque<Integer>();
Q.add( 7855642 );
Q.add( 35658786 );
Q.add( 5278367 );
Q.add( 74381793 );
System.out.println( "Queue: " + Q);
System.out.println( "Queue's head: " + Q.poll());
System.out.println( "Queue's head: " + Q.poll());
}
}
|
Output:
Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786
Reference: https://docs.oracle.com/javase/8/docs/api/java/util/Queue.html#poll–
Last Updated :
20 Oct, 2021
Like Article
Save Article
Share your thoughts in the comments
Please Login to comment...