The java.util.concurrent.ConcurrentLinkedDeque.pollFirst() is an in-built method in Java which retrieves the first element of this deque and removes it. If the deque is empty, the method returns NULL.
Syntax:
Conn_Linked_Deque.pollFirst()
Parameters: This function does not accepts any parameter.
Return Values: The function returns the first element of this deque. If this deque is empty, the function returns NULL.
Below program illustrates the use of pollFirst() method:
Program 1: This program involves deque with Integer elements.
// Java Program Demonstrate pollFirst() // method of ConcurrentLinkedDeque     import java.util.concurrent.*;  class ConcurrentLinkedDequeDemo {    public static void main(String[] args)    {        ConcurrentLinkedDeque<Integer> cld =                     new ConcurrentLinkedDeque<Integer>();          cld.addFirst(12);        cld.addFirst(70);        cld.addFirst(1009);        cld.addFirst(475);          // Displaying the existing LinkedDeque        System.out.println("Elements in"                           + "the LinkedDeque: " + cld);          // Display and remove the first element        System.out.println("Element removed : "                           + cld.pollFirst());          // Displaying the elements        System.out.println("Elements in"                           + "the LinkedDeque: " + cld);    }} |
Output:
Elements inthe LinkedDeque: [475, 1009, 70, 12] Element removed : 475 Elements inthe LinkedDeque: [1009, 70, 12]
Program 2: This program involves deque with String elements.
// Java Program Demonstrate pollFirst() // method of ConcurrentLinkedDeque     import java.util.concurrent.*;  class ConcurrentLinkedDequeDemo {    public static void main(String[] args)    {        ConcurrentLinkedDeque<String> cld =                         new ConcurrentLinkedDeque<String>();          cld.addFirst("GFG");        cld.addFirst("Geeks");        cld.addFirst("Gfg");        cld.addFirst("Geeks");          // Displaying the existing LinkedDeque        System.out.println("Elements in"                           + "the LinkedDeque: " + cld);          // Display and remove the First element        System.out.println("Element removed : "                           + cld.pollFirst());          // Displaying the elements        System.out.println("Elements in"                           + "the LinkedDeque: " + cld);    }} |
Output:
Elements inthe LinkedDeque: [Geeks, Gfg, Geeks, GFG] Element removed : Geeks Elements inthe LinkedDeque: [Gfg, Geeks, GFG]
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