The java.util.concurrent.ConcurrentLinkedDeque.removeFirstOccurrence() method is an in-built method in Java which accepts a parameter and removes the first appearance of that element in the deque. Thus, in case the element is not present in the deque, it remains unchanged. Syntax:
public boolean removeFirstOccurrence(Object o)
Parameters: The function accepts an object elem as parameter which denotes the object whose first appearance from the deque is to be removed. Return Value: The function returns true if elem is present in the deque and returns false otherwise. Exception: The function throws NullPointerException if the specified element passed as parameter to the function is null. Below programs illustrate the use of removeFirstOccurrence() method : Program 1:
Java
/* Java program to demonstrate removeFirstOccurrence() 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("gfg"); cld.addFirst("Geeks"); // Displaying the existing LinkedDeque System.out.println("Elements in " + "the LinkedDeque: " + cld); // Remove first occurrence of element cld.removeFirstOccurrence("Geeks"); // Displaying the modified LinkedDeque System.out.println("Elements in " + "the LinkedDeque: " + cld); }} |
Output:
Elements in the LinkedDeque: [Geeks, gfg, Gfg, Geeks, GFG] Elements in the LinkedDeque: [gfg, Gfg, Geeks, GFG]
Program 2:
Java
/* Java program to demonstrate removeFirstOccurrence() 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(280); cld.addFirst(1008); cld.addFirst(1050); cld.addFirst(379); // Displaying the existing LinkedDeque System.out.println("Elements in " + "the LinkedDeque: " + cld); try { // Remove first occurrence of element cld.removeFirstOccurrence(null); } catch (Exception e) { System.out.println(e); } }} |
Output:
Elements in the LinkedDeque: [379, 1050, 1008, 280, 12] java.lang.NullPointerException
