ConcurrentLinkedDeque offerLast() Method in Java

Last Updated : 26 Nov, 2018
The java.util.concurrent.ConcurrentLinkedDeque.offerLast() method is an inbuilt method in Java which inserts the specified element, passed as a parameter, to the end of the deque. Syntax: 
Conn_Linked_Deque.offerLast(Object elem)
Parameters: The method accepts a parameter elem which species the element to be inserted to the end of the deque. Return Value: The function returns True if the element is successfully added into the deque and returns False otherwise. Exception: The function throws a NullPointerException if the passed parameter is NULL. Below programs illustrate the ConcurrentLinkedDeque.offerLast() method: Program 1: Java 
/* Java Program to Demonstrate offerLast()
   method of ConcurrentLinkedDeque */

import java.util.concurrent.*;
class GFG {
    public static void main(String[] args)
    {

        // Creating an empty Deque
        ConcurrentLinkedDeque<String> cld = 
                       new ConcurrentLinkedDeque<String>();

        // Add elements into the Deque
        cld.add("Welcome");
        cld.add("To");
        cld.add("Geeks");
        cld.add("4");
        cld.add("Geeks");

        // Displaying the Deque
        System.out.println("Elements in Deque: "
                           + cld);

        // Displaying the Last element
        System.out.println("The Last element is: " + 
                                      cld.getLast());

        /* Insert an element at the tail
            of the deque */
        if (cld.offerLast("GFG")) {
            // Displaying the Last element
            System.out.println("The Inserted element is: " + 
                                              cld.getLast());
        }

        // Displaying the Deque
        System.out.println("Elements in Deque: "
                           + cld);

        // Displaying the Last element
        System.out.println("The Last element is: " + 
                                      cld.getLast());
    }
}
Output: 
Elements in Deque: [Welcome, To, Geeks, 4, Geeks]
The Last element is: Geeks
The Inserted element is: GFG
Elements in Deque: [Welcome, To, Geeks, 4, Geeks, GFG]
The Last element is: GFG
Program 2: Java 
/* Java Program to Demonstrate offerLast()
   method of ConcurrentLinkedDeque */

import java.util.concurrent.*;
class GFG {
    public static void main(String[] args)
    {

        // Creating an empty Deque
        ConcurrentLinkedDeque<Integer> cld = 
                  new ConcurrentLinkedDeque<Integer>();

        // Add elements into the Deque
        cld.add(12);
        cld.add(43);
        cld.add(29);
        cld.add(16);
        cld.add(70);

        // Displaying the Deque
        System.out.println("Elements in Deque: "
                           + cld);

        // Displaying the Last element
        System.out.println("The Last element is: " + 
                                      cld.getLast());

        try {
            cld.offerLast(null);
        }
        catch (Exception e) {
            System.out.println(e);
        }

        /* Insert an element at the tail
            of the deque */
        if (cld.offerLast(24)) {
            // Displaying the Last element
            System.out.println("The Inserted element is: "
                                          + cld.getLast());
        }

        // Displaying the Deque
        System.out.println("Elements in Deque: "
                           + cld);

        // Displaying the Last element
        System.out.println("The Last element is: " +
                                       cld.getLast());
    }
}
Output: 
Elements in Deque: [12, 43, 29, 16, 70]
The Last element is: 70
java.lang.NullPointerException
The Inserted element is: 24
Elements in Deque: [12, 43, 29, 16, 70, 24]
The Last element is: 24
Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html#offerLast()
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