//A Deque is a collection that allows us to manipulate elements from both the front and end of the collection.
//The Deque interface has two types of methods for manipulating the front and back of the collection.
//The following methods throw an exception when:
//addFirst(), addLast() - there is no space to add an element.
//removeFirst(), removeLast() - there is no element to remove.
//getFirst(), getLast() - there is no element to get.
//The following methods return a special value:
//offerFirst(), offerLast() - false when there is no space to add an element.
//pollFirst(), pollLast() - null when there is no element to remove.
//peekFirst(), peekLast() - null when there is no element to get.

Deque<String> stringDeque = new LinkedList<>();
stringDeque.addFirst("A"); // Front -> "A" <- end
stringDeque.offerFirst("B"); // Return `true` - front -> "B", "A" <- end
stringDeque.offerLast("Z"); // Returns `true` - front -> "B", "A", "Z" <- end
 
String a = stringDeque.removeFirst()  // Returns "B" - front -> "A", "Z"
String b = stringDeque.pollLast()  // Returns "Z" - front -> "A" <- back
String c = stringDeque.removeLast()  // Returns "A" - empty deque
 
String d = stringDeque.peekFirst()  // Returns null
String e = stringDeque.getLast() // Throws NoSuchElementException

// Assuming `stringDeque` has elements front -> "Mike", "Jack", "John" <- back
Iterator<String> descItr = stringDeque.descendingIterator();
 
while(descItr.hasNext()) {
  System.out.println(descItr.next());
}
// OUTPUT TERMINAL:  "John", "Jack", "Mike"