Programming Concepts and Inheritance

Constructors and Encapsulation

• Constructors in classes cannot be private as they need to be accessible to create instances of the class.
• Encapsulation is a fundamental principle in object-oriented programming, but constructors must remain public to allow object creation.

Importance of Code Reusability

• Key Principle: Avoid repeating code to enhance efficiency and maintainability.
• In programming, reusability is often achieved through inheritance, allowing shared functionality among related classes.

Inheritance Example: Animal Classes

• Defining a pet store software includes various Animal types (e.g., Dogs, Cats, Fish, Birds).
  • Dog Class:
  • Attributes: name, age
  • Methods: getName(), getAge(), setName(), setAge(), bark()
  • Cat Class:
  • Attributes: name, age
  • Methods: getName(), getAge(), setName(), setAge(), meow()
  • Fish Class:
  • Attributes: name, age, color
  • Methods: getName(), getAge(), setName(), setAge(), swim()
  • Bird Class:
  • Attributes: name, age
  • Methods: getName(), getAge(), setName(), setAge()
• Redundancy Issue: Each animal class is currently repeating the same attributes and methods, leading to inefficient code.

Using Inheritance to Improve Code

• Create a base class Animal to hold shared attributes and methods:
  • Attributes: name, age
  • Methods: getName(), getAge(), setName(), setAge()
• Benefits of Inheritance:
  • Each specific animal class (Dog, Cat, Fish, Bird) can inherit from Animal and focus only on unique features, reducing code duplication.
• This streamlines the codebase, enhances readability and maintainability.

Generalization and Specialization

• Superclass vs Subclass: A superclass (e.g., Animal) contains general characteristics, while subclasses (e.g., Dog, Cat, etc.) specialize further.
• IS-A Relationship: For example, Cat is an Animal and Dog is an Animal.

Shape Inheritance Example

• Applying the same concept to shapes:
  • Create a superclass Shape with common attributes (e.g., color).
  • Inherit it in subclasses like Circle, Rectangle, and Square.

Person Example in Inheritance

• Define a Person class:
  • Attributes: name, email, phone
  • Subclass Student inherits from Person, adding studentID and GPA.
  • Subclass Employee also inherits from Person, adding employeeID and salary.
  • This allows for efficient data representation and management.

The Object Class

• In Java, all classes inherit from the superclass Object, which serves as the root for Java inheritance.
• Contains fundamental methods like toString(), which is inherited by all classes, providing a default string representation of the object.

Generalization to Specialization

• Inheritance encompasses a spectrum from generalization (e.g., Animal) to specialization (e.g., GraduateStudent).
• This means you can create more specific classes (e.g., GraduateStudent, UndergraduateStudent) that inherit characteristics from their parent classes (e.g., Student, Person).

Relationships in Inheritance

• The relational model illustrates how classes relate to one another:
  • For example, a GraduateStudent inherits attributes from Student, which in turn inherits from Person.
• This hierarchy supports structured and maintainable code.

Considerations in Project Design

• Before coding, plan the class relationships in a project:
  • Identify common characteristics and how to implement inheritance.
• Proper organization reduces redundancy, increases efficiency, and produces cleaner code.

Practical Application and Example Code

• Start with defining classes and implementing inheritance:
  • Example for defining Animal class:
    java class Animal { private String name; private int age; // Getters and Setters }
  • Example for Dog inheriting from Animal:
    java class Dog extends Animal { public void bark() { System.out.println("Woof!"); } }
• This design approach not only simplifies implementation but also aligns with the principles of software engineering, leading to better resource management in programming.