LinkedBlockingDeque getFirst() method in Java

Last Updated : 14 Sep, 2018

The getFirst() method of LinkedBlockingDeque returns the front most element in the Deque container. If the LinkedBlockingDeque is empty, then on function call it returns a NoSuchElementException. Syntax:

public E getLast()

Parameters: This method does not accept any parameters. Returns: This method returns the first element or the head of this Deque container. Exception: The function throws only one exception i.e., NoSuchElementException when the deque is empty Below programs illustrate getFirst() method of LinkedBlockingDeque: Program 1:

Java

// Java Program Demonstrate getFirst()
// method of LinkedBlockingDeque

import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of LinkedBlockingDeque
        LinkedBlockingDeque<Integer> LBD
            = new LinkedBlockingDeque<Integer>();

        // Add numbers to front of LinkedBlockingDeque
        LBD.addFirst(7855642);
        LBD.addFirst(35658786);
        LBD.addFirst(5278367);
        LBD.addFirst(74381793);

        // before removing print queue
        System.out.println("Linked Blocking Deque: " + LBD);

        // prints the first element
        System.out.println("Linked Blocking Deque first element: " + 
                                                    LBD.getFirst());
    }
}

Output:

Linked Blocking Deque: [74381793, 5278367, 35658786, 7855642]
Linked Blocking Deque first element: 74381793

Program 2:

Java

// Java Program Demonstrate getFirst()
// method of LinkedBlockingDeque

import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of LinkedBlockingDeque
        LinkedBlockingDeque<Integer> LBD
            = new LinkedBlockingDeque<Integer>();

        // Add numbers to front of LinkedBlockingDeque
        LBD.addFirst(7855642);
        LBD.addFirst(35658786);
        LBD.addFirst(5278367);
        LBD.addFirst(74381793)

            LBD.clear();

        // Since the container is empty it will throw exception
        System.out.println("Linked Blocking Deque first element: " + 
                                                    LBD.getFirst());
    }
}

Output:

Exception in thread "main" java.util.NoSuchElementException
    at java.util.concurrent.LinkedBlockingDeque.getFirst(LinkedBlockingDeque.java:553)
    at GFG.main(GFG.java:28)

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/LinkedBlockingDeque.html#getFirst()