ArrayDeque in Java

ArrayDeque in Java provides a way to apply resizable-array in addition to the implementation of the Deque interface. It is also known as Array Double Ended Queue or Array Deck. This is a special kind of array that grows and allows users to add or remove an element from both sides of the queue. Few important features of ArrayDeque are as follows:

• Array deques have no capacity restrictions and they grow as necessary to support usage.
• They are not thread-safe which means that in the absence of external synchronization, ArrayDeque does not support concurrent access by multiple threads.
• Null elements are prohibited in the ArrayDeque.
• ArrayDeque class is likely to be faster than Stack when used as a stack.
• ArrayDeque class is likely to be faster than LinkedList when used as a queue.

Declaration:

public class ArrayDeque Element
   extends AbstractCollection
   implements DequeElement, Cloneable, Serializable

Here, Element refers to the element which can refer to any class, such as Integer or String class.

Constructors in ArrayDeque:

1. ArrayDeque(): Used to create an empty ArrayDeque and by default holds an initial capacity to hold 16 elements.
2. ArrayDeque(Collection c): Used to create an ArrayDeque containing all the elements the same as that of the specified collection.
3. ArrayDeque(int num elements): Used to create an empty ArrayDeque and holds the capacity to contain a specified number of elements.

Example:

filter_none

edit

play_arrow

brightness_4

Output:

Element : 10
Element : 20
Element : 30
Element : 40
Element : 50
Using clear() 
Above elements are removed now
Elements of deque using Iterator :
291
564
24
14
Elements of deque in reverse order :
14
24
564
291

Head Element using element(): 291
Head Element using getFirst(): 291
Last Element using getLast(): 14

Array Size : 4
Array elements :  291 564 24 14
Head element : 291
Head element poll : 291
Head element remove : 2365
The final array is: [984, 265, 564, 24, 14]

Methods in ArrayDeque:

1. add(Element e): The method inserts a particular element at the end of the deque.
2. and first(Element e): The method inserts a particular element at the start of the deque.
3. addLast(Element e): The method inserts a particular element at the end of the deque. It is similar to add() method
4. clear() : The method removes all deque elements.
5. size(): The method returns the no. of elements in the deque.
6. clone() : The method copies the deque.
7. contains(Obj): The method checks whether a deque contains the element or not
8. Iterator(): The method returns an iterator over the deque.
9. descendingIterator(): The method returns a reverse order iterator over the deque
10. element(): The method returns the element at the head of the deque
11. net first(): The method returns the first element of the deque
12. get last(): The method returns the last element of the deque
13. isEmpty(): The method checks whether the deque is empty or not.
14. toArray(): The method returns array having the elements of deque.
15. offer(Element e): The method inserts element at the end of the deque.
16. offer first(Element e): The method inserts an element at the front of the deque.
17. offerLast(Element e): The method inserts element at the end of the deque.
18. peek(): The method returns the head element without removing it.
19. seek first(): The method returns the first element without removing it.
20. peekLast(): The method returns the last element without removing it.
21. poll(): The method returns head element and also removes it
22. pollFirst(): The method returns the first element and also removes it
23. poll last(): The method returns the last element and also removes it
24. pop(): The method pops out an element for stack represented by deque
25. push(Element e): The method pushes an element onto stack represented by deque
26. remove(): The method returns head element and also removes it
27. remove first(): The method returns the first element and also removes it
28. removes last(): The method returns the last element and also removes it
29. remove first occurrence(Obj): The method removes the element where it first occurs in the deque.
30. remove last occurrence(Obj): The method removes the element where it last occurs in the deque.

Related Articles:

• Java.util.ArrayDeque Class in Java | Set 1
• Java.util.ArrayDeque Class in Java | Set 2