feat: Implement example demonstrating upcasting and downcasting in Java with method overriding

This commit adds a Java program that illustrates key object-oriented programming concepts:
- Upcasting (child to parent reference)
- Downcasting (parent reference back to child)
- Method overriding and dynamic method dispatch

Key changes:
- Defined a `Parent` class with a `name` attribute and a `method()` printing a message
- Defined a `Child` class that extends `Parent`, adds an `id` attribute, and overrides the `method()`
- In the `main()` method:
  - Performed **upcasting**: `Parent p = new Child();` and demonstrated access to inherited fields and overridden methods
  - Showed **method dispatch behavior**: `p.method()` executes the overridden method in `Child`
  - Performed **explicit downcasting** safely: `(Child)p` to access subclass-specific field `id`
  - Printed both inherited and child-specific data to verify proper object behavior after downcasting

This example reinforces Java's runtime polymorphism and the correct approach to accessing subclass features after safe downcasting.

Signed-off-by: Somesh diwan <[email protected]>

Author: Someshdiwan

Section5OperatorExpression/src/UpDownCasting.java

@@ -1,32 +1,37 @@
 class Parent {
     String name;
-    void method()
-    {
+
+    void method() {
         System.out.println("Method from Parent");
     }
 }
+
 class Child extends Parent {
     int id;
-    @Override void method()
-    {
+
+    @Override
+    void method() {
         System.out.println("Method from Child");
     }
 }
+
 public class UpDownCasting {
-    public static void main(String[] args)
-    {
+    public static void main(String[] args) {
+
         /*Upcasting*/
         Parent p = new Child();
         p.name = "Up Casting";
         System.out.println(p.name);
+
         /*parent class method is overridden method hence this will be executed*/
         p.method();
 
         /* Trying to Downcasting Implicitly Child c = new Parent(); - > compile time error Downcasting Explicitly*/
         Child c = (Child)p;
         c.id = 1;
+
         System.out.println(c.name);
         System.out.println(c.id);
         c.method();
     }
-}
+}