The java.util.concurrent.ConcurrentLinkedDeque.addFirst() is an in-built function in Java which inserts the specified element at the front of the ConcurrentLinkedDeque.
Syntax:
conn_linked_deque.addFirst(elem)
Parameter: The method accepts only a single parameter elem which is to be added to the beginning of the ConcurrentLinkedDeque.
Return Value: The function has no return value.
Exception:The method will throw NullPointerException when the parameter passed to the function is null. Due to its bounded nature, this method will never throw IllegalStateException or return false.
Below programs illustrate the ConcurrentLinkedDeque.addFirst() method:
Program 1: This program involves a ConcurrentLinkedDeque of Integer type.
// Java Program Demonstrate addFirst()// method of ConcurrentLinkedDeque   import java.util.concurrent.*;  class ConcurrentLinkedDequeDemo {    public static void main(String[] args)    {        ConcurrentLinkedDeque<Integer> cld =                      new ConcurrentLinkedDeque<Integer>();          cld.addFirst(12);        cld.addFirst(110);        cld.addFirst(55);        cld.addFirst(76);          // Displaying the existing LinkedDeque        System.out.println("Initial Elements in"                           + "the LinkedDeque: " + cld);          // Insert a new element in the LinkedDeque        cld.addFirst(21);          // Displaying the modified LinkedDeque        System.out.println("Initial Elements in"                           + "the LinkedDeque: " + cld);    }} |
Initial Elements inthe LinkedDeque: [76, 55, 110, 12] Initial Elements inthe LinkedDeque: [21, 76, 55, 110, 12]
Program 2: This program involves a ConcurrentLinkedDeque of Integer type with Exception Handling when null is passed as parameter to the function.
// Java Program Demonstrate addFirst()// method of ConcurrentLinkedDeque   import java.util.concurrent.*;  class ConcurrentLinkedDequeDemo {    public static void main(String[] args)    {        ConcurrentLinkedDeque<String> cld =                          new ConcurrentLinkedDeque<String>();          cld.addFirst("Geeks");        cld.addFirst("Geek");        cld.addFirst("Gfg");        cld.addFirst("Contribute");          // Displaying the existing LinkedDeque        System.out.println("Initial Elements in"                           + "the LinkedDeque: " + cld);          /* Exception thrown when null              is passed as parameter*/        try {            cld.addFirst(null);        }        catch (NullPointerException e) {            System.out.println("NullPointerException"                               + "thrown");        }          // Insert a new element in the LinkedDeque        cld.addFirst("Sudo Placement");          // Displaying the modified LinkedDeque        System.out.println("Initial Elements in"                           + "the LinkedDeque: " + cld);    }} |
Initial Elements inthe LinkedDeque: [Contribute, Gfg, Geek, Geeks] NullPointerExceptionthrown Initial Elements inthe LinkedDeque: [Sudo Placement, Contribute, Gfg, Geek, Geeks]
Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html#addFirst()
