feat: add ArrayDequeDemo demonstrating double-ended queue operations in Java

Implemented ArrayDequeDemo.java to illustrate how ArrayDeque supports both queue
(FIFO) and stack (LIFO) behaviors. Demonstrates insertion using offerFirst(),
offerLast() and removal with pollFirst(), pollLast(), highlighting its O(1)
performance and flexibility as a non-thread-safe, resizable array-based deque.

Signed-off-by: https://github.com/Someshdiwan <someshdiwan369@gmail.com>

Author: Someshdiwan

Section 25 Collections Frameworks/Queue Interface/Deque/Array Deque/src/ArrayDequeDemo.java

@@ -4,7 +4,7 @@ public class ArrayDequeDemo {
     public static void main(String[] args) {
     ArrayDeque<Integer> DQ  = new ArrayDeque<>();
     /*
-    new ArrayDeque<>();  Constructor.
+    new ArrayDeque<>(); // Constructor.
     Takes Constant time.
     */
 
@@ -13,14 +13,14 @@ public static void main(String[] args) {
     DQ.offerLast(40);
     DQ.offerLast(30);
 
-    //DQ.pollFirst(); //Inserting from last and deleting from first.Acting like a Queue.
-    //DQ.pollLast();  //Stack delete and insert from last.
+    // DQ.pollFirst(); // Inserting from last and deleting from first.Acting like a Queue.
+    // DQ.pollLast();  // Stack delete and insert from last.
 
-/*  DQ.offerFirst(1);
+    /*
+    DQ.offerFirst(1);
     DQ.offerFirst(2);
     DQ.offerFirst(3);
-*/
-
-    DQ.forEach((x)-> System.out.println(x));
+    */
+        DQ.forEach((x)-> System.out.println(x));
     }
-}
+}