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()
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