Question

Create an abstract class Breakfast with two abstract methods checkCarb () , and checkNutrients(). If carb count is less than 200 , breakfast is healthy. If it contains all nutrients such as vitamins, minerals etc, breakfast is healthy. Create three sub classes Indian, Mediterranean and Chinese and all subclasses should override the two abstract methods by providing appropriate implementations. Create a public class that will create objects of these three breakfast implementations, and call implementation methods.

Short answer

Define the abstract class `Breakfast` with abstract methods. Extend in `Indian`, `Mediterranean`, `Chinese` classes and override the methods. Implement a main class to test.

Step-by-step solution

- Define the Abstract Class

Define an abstract class named `Breakfast` with two abstract methods `checkCarb()` and `checkNutrients()`. Both methods should not have any implementation inside the abstract class.

- Define the Subclasses

Create three subclasses `Indian`, `Mediterranean`, and `Chinese` that extend the `Breakfast` class. Override the `checkCarb()` and `checkNutrients()` methods in each of these subclasses and provide appropriate implementations.

- Implement the checkCarb() Method

In each subclass (Indian, Mediterranean, Chinese), implement the `checkCarb()` method to check if the carb count is less than 200. If it is, the method should return `true`, indicating the breakfast is healthy. Otherwise, it should return `false`.

- Implement the checkNutrients() Method

In each subclass, implement the `checkNutrients()` method to check if the breakfast contains all necessary nutrients such as vitamins and minerals. If it does, the method should return `true`. Otherwise, it should return `false`.

- Create a Public Class with Main Method

Create a public class (for example, `Main`) that contains the `main` method. Inside the main method, create objects of the `Indian`, `Mediterranean`, and `Chinese` subclasses, and call their `checkCarb()` and `checkNutrients()` methods.

Key concepts

Java Inheritance

In Java, inheritance allows a class to inherit properties and methods from another class. This promotes code reusability and establishes a relationship between the parent (or superclass) and child (or subclass) classes. When creating the `Breakfast` class as an abstract class, it serves as a blueprint for its subclasses (`Indian`, `Mediterranean`, and `Chinese`). These subclasses inherit the abstract methods `checkCarb()` and `checkNutrients()` and must provide specific implementations.

Inheritance helps to:

• Reduce code duplication
• Bring consistency when methods are defined in the superclass
• Facilitate polymorphism, allowing objects of subclasses to be treated as objects of the superclass

Abstract Methods

Abstract methods in Java are methods that are declared in an abstract class without any implementation. These methods only have a method signature and must be defined in non-abstract subclasses. For instance, the `Breakfast` class declares `checkCarb()` and `checkNutrients()` as abstract methods. When these methods are overridden in the `Indian`, `Mediterranean`, and `Chinese` subclasses, they provide specific behaviors for determining if a type of breakfast is healthy.

Key points about abstract methods:

• They cannot have a body; only the method signature is provided.
• They must be overridden by subclasses.
• They enforce a contract for subclasses to follow and implement.

Method Overriding

Method overriding occurs when a subclass provides a specific implementation for a method already defined in its superclass. This allows the subclass to offer its own behavior while still adhering to the method's signature. In our example, the `Indian`, `Mediterranean`, and `Chinese` subclasses override `checkCarb()` and `checkNutrients()`. This lets each subclass define what makes their breakfast variant healthy.

Takeaways from method overriding:

• Allows customization and extension of an existing method.
• Helps implement runtime polymorphism (objects determining methods to execute at runtime).
• Makes the subclass more specialized while keeping a consistent method interface.

Object-Oriented Programming

Java is a powerful object-oriented programming (OOP) language. OOP revolves around objects and classes, bringing four major principles: encapsulation, inheritance, polymorphism, and abstraction. The exercise on creating a healthy breakfast system encompasses these principles through:

1. **Encapsulation:** Each breakfast subclass manages its own data and methods like `checkCarb()` and `checkNutrients()`.
2. **Inheritance:** The subclasses inherited abstract methods from the `Breakfast` class and provided specific implementations.
3. **Polymorphism:** Different breakfast objects (`Indian`, `Mediterranean`, `Chinese`) were treated uniformly as `Breakfast` objects in the public class with the main method.
4. **Abstraction:** The abstract class `Breakfast` hides the complexity of method implementations, providing a simplified abstract view.

OOP is essential because it helps in managing complex software, promotes code reuse, and makes code more adaptable and maintainable.