The java.util.concurrent.ConcurrentLinkedDeque.peekFirst() is an in-built method in Java which
retrieves the first element of this deque without removing it. The function returns NULL if the deque is empty.
Syntax:
Conn_Linked_Deque.peekFirst()
Parameters: This function does not accepts any parameter.
Return Values: The function returns the first element present in this deque and returns NULL when the deque is empty.
Below programs illustrate the peekFirst() method:
Program 1: This program involves deque with Integer elements.
// Java Program Demonstrate peekFirst()// 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(110); cld.addFirst(55); cld.addFirst(76); // Displaying the existing LinkedDeque System.out.println("Elements in" + "the LinkedDeque: " + cld); // Displaying the first element System.out.println("First Element in" + "the LinkedDeque: " + cld.peekFirst()); }} |
Output:
Elements inthe LinkedDeque: [76, 55, 110, 12] First Element inthe LinkedDeque: 76
Program 2: This program involves deque with String elements.
// Java Program Demonstrate peekFirst()// 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("Gfg"); cld.addFirst("Lazyroar"); cld.addFirst("Geeks"); // Displaying the existing LinkedDeque System.out.println("Elements in" + "the LinkedDeque: " + cld); // Displaying the First element System.out.println("First Element in" + "the LinkedDeque: " + cld.peekFirst()); }} |
Output:
Elements inthe LinkedDeque: [Geeks, Lazyroar, Gfg, GFG] First Element inthe LinkedDeque: Geeks
