Implement a Shape interface using OOP

## Problem You are given the following interface (language-agnostic): ```text interface Shape { double area(); double perimeter(); } ``` Design and implement concrete classes for common shapes (at minimum): - `Circle(radius)` - `Rectangle(width, height)` Optionally add one more shape (e.g., `Triangle(a,b,c)` or `Square(side)`). ### Requirements - Use OOP best practices (encapsulation, clear naming, polymorphism). - Validate inputs (e.g., non-negative dimensions; for triangle, triangle inequality). - Make objects safe to use (e.g., immutable fields if possible). - Provide a small example showing how a caller can compute total area/perimeter of a list of `Shape` objects. ## What to submit - Class definitions + brief demonstration code (no need for UI).