The
addFirst(E e) method of
Deque Interface inserts the element passed in the parameter to the front of the Deque if there is space. If the Deque is capacity restricted and no space is left for insertion, it returns an
IllegalStateException. The function returns true on successful insertion.
Syntax:
void addFirst(E e)
Parameters: This method accepts a mandatory parameter
e which is the element to be inserted to the front of the Deque.
Returns: This method returns true on successful insertion.
Exceptions: The function throws four exceptions which are described as below:
- ClassCastException: when the class of the element to be entered prevents it from being added to this container.
- IllegalStateException: when the capacity of the container is full and insertion is done.
- IllegalArgumentException: when some property of the element prevents it to be added to the Deque.
- NullPointerException: when the element to be inserted is passed as null and the Deque's interface does not allow null elements.
Below programs illustrate
addFirst() method of Deque:
Program 1: With the help of
LinkedList.
Output:
Deque: [74381793, 5278367, 35658786, 7855642]
Program 2: With the help of
ArrayDeque.
Output:
Deque: [74381793, 5278367, 35658786, 7855642]
Program 3: With the help of
ConcurrentLinkedDeque.
Output:
Deque: [74381793, 5278367, 35658786, 7855642]
Program 4: With the help of
LinkedBlockingDeque.
Output:
Deque: [74381793, 5278367, 35658786, 7855642]
Below programs illustrate
exceptions thrown by addFirst() method:
Program 5: To show
NullPointerException.
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:20)
Program 6: To show
IllegalStateException.
