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 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 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()
