feat(ArrayListDemo2): demonstrate basic ArrayList operations (add, contains, iteration)

What
- Added ArrayListDemo2 class.
- Created an ArrayList<Integer> with default capacity (10).
- Inserted three elements: 1, 5, 80.
- Demonstrated:
  - contains(Object) → check for presence of values.
  - Iteration using enhanced for-each loop.
  - Iteration using index-based for loop.
- Included commented examples showing:
  - get(index) usage.
  - size() retrieval.
  - remove(index), add(index, value), and set(index, value) for element modification.

Why
- Provides a hands-on demo of common ArrayList methods.
- Highlights difference between size and capacity.
- Shows safe element access vs exceptions when index is out of bounds.
- Illustrates multiple iteration styles.

How
- List.add(1), add(5), add(80) → List = [1, 5, 80].
- List.contains(5) → true.
- List.contains(50) → false.
- For-each loop prints elements one by one.
- Index-based for loop uses size() and get(i) to print elements.

Logic
- Inputs: integers 1, 5, 80.
- Outputs:
  - Boolean results for contains() checks.
  - Printed list elements via two loop styles.
- Flow:
  1. Create ArrayList.
  2. Add three elements.
  3. Test membership (contains).
  4. Iterate with for-each.
  5. Iterate with indexed loop.
- Edge cases:
  - get(3) would throw IndexOutOfBoundsException since size=3 (valid indices 0–2).
  - remove(index) throws if index invalid.
- Complexity:
  - add(E): amortized O(1).
  - contains(Object): O(n).
  - get(index): O(1).
  - remove(index), add(index,E), set(index,E): O(n) worst case due to shifting.
- Concurrency: ArrayList not thread-safe.

Real-life applications
- Building simple lists of integers, objects, or IDs.
- Membership checks with contains().
- Choosing iteration style depending on readability vs need for indices.
- Demonstrating dynamic growth compared to primitive arrays.

Notes
- Default capacity = 10, grows as needed.
- For-each is concise for read-only traversal.
- Index-based loop useful when modifying elements or needing positions.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section25CollectionFramework/src/ListDemo/ArrayListLinkedListStack/ListED.java renamed to Section 25 Collections Frameworks/List Interface/ArrayList/src/ArrayListDemo2.java

@@ -1,35 +1,33 @@
-package ListDemo.ArrayListLinkedListStack;
-
 import java.util.ArrayList;
 
-public class ListED {
+public class ArrayListDemo2 {
     public static void main(String[] args) {
         ArrayList<Integer> List = new ArrayList<>(); //Default capacity 10.
 
         List.add(1); //Index Zero
         List.add(5); //Index One
         List.add(80); //Index Two
 
-        //System.out.println(List.get(3)); //Throw exception
-        //System.out.println(List.get(2));
-        //System.out.println(List.size());
+        // System.out.println(List.get(3));
+        // Throw exception
+
+        // System.out.println(List.get(2));
+        // System.out.println(List.size());
 
         System.out.println(List.contains(5));
         System.out.println(List.contains(50));
 
-/*        for(int i=0; i<List.size(); i++)
-        {
-            System.out.println(List.get(i));
-        }
-*/
-
-     /*
+        /*
         List.remove(2);
         List.add(2,100);
         List.set(2,1000);
-     */
+        */
 
         for(int x:List)
-            System.out.println(x);
+            System.out.print(x+" "+"\n");
+
+        for(int i=0; i<List.size(); i++) {
+            System.out.print(List.get(i)+" ");
+        }
     }
-}
+}