ConcurrentLinkedDeque offer() method in Java with Examples

The java.util.concurrent.ConcurrentLinkedDeque.offer() method is an inbuilt method in Java which inserts the specified element, passed as a parameter, to the deque.

Syntax:

public boolean offer(E elem)

Parameters: The method accepts a parameter elem which species the element to be inserted to 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.offer() method:

Program 1:

// Java Program to Demonstrate offer()
// 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("ConcurrentLinkedDeque: "
                           + cld);

        // Insert an element using offer()
        if (cld.offer("GFG")) {

            // Displaying message
            System.out.println("Element Inserted");
        }
        else {

            // Displaying message
            System.out.println("Element not Inserted");
        }

        // Displaying the Deque
        System.out.println("ConcurrentLinkedDeque: "
                           + cld);
    }
}

Output:

ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks]
Element Inserted
ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks, GFG]

// Java Program to Demonstrate offer()
// 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("ConcurrentLinkedDeque: "
                           + cld);

        try {

            // Insert null element using offer()
            cld.offer(null);
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

Output:

ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks]
java.lang.NullPointerException

Reference: https://docs.oracle.com/javase/9/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html#offer-E-