The addFirst(E e) method of BlockingDeque inserts the element passed in the parameter to the front of the Deque if there is space. If the BlockingDeque is capacity restricted and no space is left for insertion, it returns an IllegalStateException.
Syntax:
public void addFirst(E e)
Parameters: This method accepts a mandatory parameter e which is the element to be inserted in the front of the BlockingDeque.
Returns: This method does not returns anything.
Exception:
- IllegalStateException: if the element cannot be added at this time due to capacity restrictions
- NullPointerException: if the specified element is null
Note: The addFirst() method of BlockingDeque has been inherited from the LinkedBlockingDeque class in Java.
Below programs illustrate addFirst() method of BlockingQueue:
Program 1:
// Java Program Demonstrate addFirst()// method of BlockingDeque  import java.util.concurrent.LinkedBlockingDeque;import java.util.concurrent.BlockingDeque;import java.util.*;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of BlockingDeque        BlockingDeque<Integer> BD            = new LinkedBlockingDeque<Integer>();          // Add numbers to front of BlockingDeque        BD.addFirst(7855642);        BD.addFirst(35658786);        BD.addFirst(5278367);        BD.addFirst(74381793);          // before removing print Dequq        System.out.println("Blocking Deque: " + BD);    }} |
Output:
Blocking Deque: [74381793, 5278367, 35658786, 7855642]
Program 2:
// Java Program Demonstrate addFirst()// method of BlockingDeque// when it is Fullimport java.util.concurrent.LinkedBlockingDeque;import java.util.concurrent.BlockingDeque;import java.util.*;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of BlockingDeque        // size of list        BlockingDeque<Integer> BD            = new LinkedBlockingDeque<Integer>(3);          // Add numbers to front of BlockingDeque        BD.addFirst(7855642);        BD.addFirst(35658786);        BD.addFirst(5278367);          // it is full        BD.addFirst(74381793);          // before removing print Deque        System.out.println("Blocking Deque: " + BD);    }} |
Output:
Exception in thread "main" java.lang.IllegalStateException: Deque full
at java.util.concurrent.LinkedBlockingDeque.addFirst(LinkedBlockingDeque.java:326)
at GFG.main(GFG.java:24)
Program 3:
// Java Program Demonstrate addFirst()// method of BlockingDeque// when nill is inserted  import java.util.concurrent.BlockingDeque;import java.util.concurrent.LinkedBlockingDeque;import java.util.*;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of BlockingDeque        BlockingDeque<Integer> BD            = new LinkedBlockingDeque<Integer>();          // Add numbers to front of BlockingDeque        BD.addFirst(7855642);        BD.addFirst(35658786);        BD.addFirst(5278367);          // NULL        BD.addFirst(null);          // before removing print Deque        System.out.println("Blocking Deque: " + BD);    }} |
Output:
Exception in thread "main" java.lang.NullPointerException
at java.util.concurrent.LinkedBlockingDeque.offerFirst(LinkedBlockingDeque.java:342)
at java.util.concurrent.LinkedBlockingDeque.addFirst(LinkedBlockingDeque.java:325)
at GFG.main(GFG.java:24)
Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingDeque.html#addFirst(E)
