ConcurrentLinkedDeque getFirst() method in Java

The java.util.concurrent.ConcurrentLinkedDeque.getFirst() method is an in-built method in Java which returns the first element of the deque container.

Syntax:

Conn_Linked_Deque.getFirst()

Parameters: The method does not accept any parameter.

Return Value: The method returns the first element present in the Deque.

Exception: The function throws a NoSuchElementException when the deque is empty.

Below programs illustrate the ConcurrentLinkedDeque.getFirst() method :

Program 1:

/* Java Program to Demonstrate getFirst()
   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 the Deque: " + cld);

        // Displaying the first element
        System.out.println("The first element is: " +
                                      cld.getFirst());
    }
}

Output:

Elements in the Deque: [Welcome, To, Geeks, 4, Geeks]
The first element is: Welcome

Program 2:

/* Java Program to Demonstrate getFirst()
   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>();

        try {
            // Displaying the first element
            System.out.println("The first element "
                               + "is: " + cld.getFirst());
        }
        catch (Exception e) {
            System.out.println(e);
        }

        // 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 the Deque: " + cld);

        // Displaying the first element
        System.out.println("The first element is: " +
                                       cld.getFirst());
    }
}

Output:

java.util.NoSuchElementException
Elements in the Deque: [12, 43, 29, 16, 70]
The first element is: 12

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