ConcurrentLinkedDeque removeLastOccurrence() Method in Java

The java.util.concurrent.ConcurrentLinkedDeque.removeLastOccurrence() method is an in-built method in Java which accepts a parameter and removes the last appearance of that element in the deque. Thus, in case the element is not present in the deque, it remains unchanged. Syntax:

public boolean removeLastOccurrence(Object o)

Parameters: The function accepts an object elem as parameter which denotes the object whose last 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 removeLastOccurrence() method : 

Java

/* Java program to demonstrate
   removeLastOccurrence() 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 last occurrence of  element
        cld.removeLastOccurrence("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: [Geeks, gfg, Gfg, GFG]

Program 2:

Java

/* Java program to demonstrate
   removeLastOccurrence() 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 last occurrence of  element
            cld.removeLastOccurrence(null);
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

Output:

Elements in the LinkedDeque: [379, 1050, 1008, 280, 12]
java.lang.NullPointerException

Reference:https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html#removeLastOccurrence()