feat(generics): illustrate benefits of generics with ArrayList vs raw types

WHAT:
- Added `WhyGenerics` class to demonstrate type safety provided by generics.
- Compared raw `ArrayList` (pre-Java 5 style) with `ArrayList<String>` using generics.
- Highlighted issues of manual casting and potential runtime `ClassCastException`.

WHY:
- Without generics (`ArrayList list = new ArrayList();`), collections can store any type, but retrieving requires explicit casting.
- This leads to runtime errors if incompatible types are stored (e.g., adding `Integer` and casting to `String`).
- With generics (`ArrayList<String>`), the compiler enforces type safety, eliminating the need for casts.

HOW:
- Created an `ArrayList<String>` and safely added string elements ("Hello", "World").
- Retrieved elements without explicit casts, ensuring compile-time safety.
- Demonstrated commented-out examples of adding integers/doubles, showing compile-time prevention of unsafe operations.
- Added example of forced casting with raw types to show type safety issues.

BENEFITS:
- Generics eliminate the need for repetitive casting.
- Errors are caught at compile time instead of runtime.
- Improves code readability, maintainability, and safety.

REAL-WORLD APPLICATIONS:
- Common in Collections Framework (`List<T>`, `Map<K,V>`, `Set<T>`).
- Used heavily in frameworks like Spring, Hibernate, and Java Streams to ensure type safety.
- Prevents runtime crashes in enterprise-grade applications by leveraging compile-time type checks.

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

Author: Someshdiwan

Section24JavaGenerics/src/WhyGenerics.java renamed to Section24JavaGenerics/src/Generics/WhyGenerics.java

@@ -1,8 +1,9 @@
+package Generics;
+
 import java.util.ArrayList;
 
 public class WhyGenerics {
-    public static void main(String[] args)
-    {
+    public static void main(String[] args) {
         //ArrayList list =new ArrayList();
 
         ArrayList<String> list = new ArrayList<>();
@@ -13,16 +14,18 @@ public static void main(String[] args)
         String s11 = list.get(1);
 
         System.out.println(s);
+        System.out.println(s11);
 
         //list.add(123);
         //list.add(3.14);
 
-        //String str = list.get(0); //Cast karna padega string mai list nahi jata.
+        //String str = list.get(0);
+        //Cast karna padega string mai list nahi jata.
         //Parent class and child class.
 
         String str = (String) list.get(0);
-
-        String integer = (String) list.get(1); //int to string can not cast.
+        String integer = (String) list.get(1);
+        //int to string can not cast.
         //Issue: Type Safety issue and Manual Casting.(Without generics) No compile time checking.
     }
-}
+}