feat(generic-interface): implement Container<String> with StringContainer1

WHAT:
- Added `StringContainer1` class implementing the generic `Container<String>` interface.
- Provides type-safe storage and retrieval of `String` values.
- Encapsulates a `String` item with:
  - `add(String item)` → stores the string.
  - `get()` → retrieves the stored string.

WHY:
- Demonstrates a **concrete implementation** of a generic interface with a fixed type (`String`).
- Highlights how generics can be narrowed down when implementing to enforce strict type usage.

HOW (Logic Flow):
1. Define `StringContainer1` that implements `Container<String>`.
2. Implement `add()` to assign a `String` value to the private field.
3. Implement `get()` to return the stored `String`.

BENEFITS:
- Type safety: only `String` values can be added (compile-time enforcement).
- No need for type casting when retrieving values.
- Clear demonstration of how a generic interface can be specialized for a single type.

REAL-WORLD APPLICATIONS:
- Useful in cases where a container is designed for one specific type (e.g., message queues holding only text).
- Mirrors patterns in frameworks where type constraints are locked at implementation to reduce misuse.

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

Author: Someshdiwan

Section24JavaGenerics/src/GenericInterface/StringContainer1.java

@@ -11,8 +11,8 @@ public String get() {
         return item;
     }
 }
-//In this example, StringContainer implements the Container interface with String as the specified type parameter.
 
+//In this example, StringContainer implements the Container interface with String as the specified type parameter.
 
 /*
 class GenericContainer<T> implements Container<T> {