feat(Phone): add simple Phone class with brand and model fields

What
- Introduced `Phone` class with:
  • Two fields: `brand` and `model`.
  • Constructor to initialize both fields.
  • Overridden `toString()` method for readable object representation.

Why
- Provides a minimal data model to represent phone objects.
- Useful as a building block for demos, collections, or further feature expansions.

How
- Inputs:
  - `brand` (String), `model` (String) passed to constructor.
- Outputs:
  - `toString()` returns formatted string: Phone{brand='...', model='...'}.
- Flow:
  1. Instantiate Phone with brand and model.
  2. Use `toString()` when printing/logging.
- Complexity:
  - O(1) for construction and string rendering.

Real-life applications
- Can be used in inventory systems, e-commerce product catalogs, or mobile databases.
- Acts as a simple DTO (Data Transfer Object) in APIs.

Notes
- Class is minimal and does not include equals/hashCode (not needed for this simple demo).
- Can be extended later with price, year, specs, etc.

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

Author: Someshdiwan

Section 25 Collections Frameworks/Map Interface/Garbage Collection/src/Phone.java

@@ -0,0 +1,19 @@
+public class Phone {
+    String brand;
+    String model;
+
+    public Phone(String brand, String model) {
+        this.brand = brand;
+        this.model = model;
+    }
+
+    @Override
+    public String toString() {
+        return "Phone{" +
+                "brand='" + brand + '\'' +
+                ", model='" + model + '\'' +
+                '}';
+    }
+}
+
+// A simple class to represent a phone object.