Problem Statement: Simple Vehicle & Car

Your task is to create two simple Java classes to represent a **Vehicle** and a **Car**. The goal is to understand a fundamental concept of object-oriented programming: **Inheritance**. You will learn how one class (Car) can get features from another class (Vehicle).

Functional Requirements

Vehicle Class: A basic vehicle should have a brand (e.g., "Ford") and a way to make a sound.
Car Class: A car is a type of vehicle. It should inherit all the features of a vehicle and also have its own unique feature, like the number of doors.
Actions:
- The Vehicle should be able to "honk".
- The Car should be able to "start the engine".

Technical Requirements

Create a Vehicle Class: This will be your parent class. It should have a public field for brand and a public method honk() that prints "The vehicle is honking!".
Create a Car Class: This will be your child class. It must **inherit** from the Vehicle class using the extends keyword. It should have its own public field for numberOfDoors and a public method startEngine() that prints "The car engine is started.".
Demonstrate in Main: In your main method, create a single object of the Car class.
- Set the car's brand and number of doors.
- Call both the honk() method (from the `Vehicle` class) and the startEngine() method (from the `Car` class) on the same car object.

Testing Requirements

Your main method must demonstrate the program works by testing the following scenario:

Car Object Test:
- Create a Car object and assign it a brand (e.g., "Toyota") and number of doors (e.g., 4).
- Call the `startEngine()` method. The output should confirm the engine started.
- Call the `honk()` method. The output should confirm the vehicle is honking.
- This test shows that the `Car` object has access to both its own methods and the methods it inherited from the `Vehicle` class.