Object-Oriented Programming in Java.pdf

Object-Oriented Programming in Java
Java is a well-liked programming language that may be used to create a wide range of
applications, from straightforward desktop programs to intricate web programs. It is an
object-oriented programming language that enables programmers to create modular, reusable
code, making it simple to maintain and update.
We shall look at the fundamentals of Java object-oriented programming in this tutorial. The
fundamentals of object-oriented programming in Java, oops concepts such as classes and
objects, inheritance, polymorphism, and encapsulation will all be covered. You will have a solid
understanding of object-oriented programming in Java and how to use it to create robust and
scalable programs at the end of this article.

Introduction to OOPs concept
Object-oriented programming in Java is a programming paradigm that revolves around objects.
An object is a real-world entity that has a set of attributes and behaviors. In Java, even basic
data types like integers and booleans are considered objects.
In OOPS, a program is designed by creating objects that interact with each other to perform
tasks. Objects have attributes that define their properties and methods that define their
behavior.
In Java, we create classes, which are templates that define the attributes and behaviors of
objects. A class can be compared to an object creation blueprint. Once a class is defined,
objects can be created based on that class.
Principles of Object-Oriented Programming
There are four main principles of object-oriented programming:
a. Abstraction
Abstraction is the process of hiding complex details and providing a simplified interface for the
user. It helps developers to create simpler and more understandable models of a complex
system, by just exposing only the required features and not the implementation part. In Java,
abstraction can be achieved using interfaces and abstract classes.
b. Encapsulation
Encapsulation is the process of hiding the internal details of an object and providing a public
interface for accessing and modifying the object. It helps in maintaining the integrity of the object
and ensures that its internal state cannot be modified by external code. In Java, encapsulation
can be achieved using access modifiers such as public, private, and protected.
Got confused between Abstraction and Encapsulation?
Abstraction is about simplifying the complexity of a system by focusing on its essential features,
while encapsulation is about protecting the integrity of an object by hiding its internal details.
c. Inheritance
The process of creating a new class from an existing one is called Inheritance. The new class
inherits the attributes and behaviors of the existing class and can add additional attributes and
behaviors. This helps in reducing code duplication, promoting code reuse, and making the code
more modular and maintainable. In Java, the extend keyword is useful for achieving
inheritance.

d. Polymorphism
The ability of an object to take on multiple forms is known as polymorphism. The Java language
supports polymorphism through method overloading and method overriding.
Classes and Objects in Java
A class is a blueprint for creating objects. It defines the attributes and behaviors of an object. An
object is an instance of a class. It has a unique set of characteristics and behaviors.
To create a class in Java, use the following syntax:
Let's see an example to understand
1. Class Creation - You can use the class keyword to create a class.
2. Object - It can be created using a new keyword.
3. Method
public class CodeAvinya {
static String name;
static float salary;
static void set(String n, float p) {
name = n;
salary = p;
}
static void get() {
System.out.println("Employee name is: " + name );
System.out.println("Employee CTC is: " + salary);
}
public static void main(String args[]) {
// object
CodeAvinya obj = new CodeAvinya();
obj.set("Rajesh", 15000.0f);
obj.get();
}
}
To create an object based on a class, use the following syntax:
MyClass obj = new MyClass();

Inheritance
The technique of building a new class from an existing one is called inheritance. The new class
inherits the attributes and behaviors of the existing class and can add additional attributes and
behaviors.
To create a subclass in Java, use the following syntax:
public class MySubclass extends MyClass{
// subclass body
}
Polymorphism
Polymorphism refers to an object's capacity to assume various forms. The overloading and
overriding of methods are two ways to implement polymorphism in Java. This allows developers
to reuse existing code and also create new classes which are tailored to the specific application
or system.
Creating multiple methods with the same name but different parameters is called method
overloading. Method overriding is the process of creating a new implementation of a method
that already exists in a superclass.
Encapsulation
Encapsulation, like a class in Java, describes grouping together data and functions that operate
on that data into a single unit. This idea is frequently used to conceal the internal representation
or state of an entity. We refer to this as hiding of the information. In Java, this is achieved by
using access modifiers such as public, private, and protected. Encapsulation helps to ensure
that the data inside an object is only accessible through a well-defined interface, which allows
for improving security and maintainability.
Abstraction
Abstraction is the process of hiding complex implementation details behind a more
straightforward interface.Java interfaces and abstract classes are used for achieving
abstraction. By using abstraction, developers can create code that is easier to understand and
maintain, as complex implementation details are hidden from the outside world.

1. Abstraction in Java: Object-Oriented
Programming
As a famous object-oriented programming language, Java offers a variety of tools for
developers to design efficient, reusable, and maintainable software solutions. One of the most
significant ideas in Java is an abstraction, which lets developers focus on the key elements of a
software system while obscuring superfluous details. In this post, we'll discuss the principles of
abstraction in Java, how it works, and why it's a vital subject to understand for any Java
developer.
1.1 Introduction to Object-Oriented Programming
Object-Oriented Programming (OOP) is a programming paradigm that is built on the idea of
objects, which represent real-world entities with a collection of properties (data) and behaviors
(methods). Java is one of the most popular object-oriented programming languages, which
offers a broad collection of capabilities and tools for constructing scalable, dependable, and
maintainable software systems.
1.2 What is Abstraction?

Abstraction is a key principle in object-oriented programming that allows developers to focus on
the important elements of a software system while obscuring extraneous details. Abstraction is
achieved by the use of abstract classes and methods, which specify a collection of common
traits that are shared by a group of related objects.
1.3 Abstract Classes and Methods
In Java, abstract classes and methods are used to define the common aspects of a group of
related objects without implementing them. A class that cannot be made but can be subclassed
is abstract. It could incorporate both non-abstract and abstract approaches. A technique that
has been specified but not used is abstract. It must be implemented by the real subclass that
extends the abstract class.
1.4 Implementing Abstraction in Java
To implement abstraction in Java, you must design an abstract class that specifies the common
attributes of a group of related objects. You can then design concrete subclasses that extend
the abstract class and implement the abstract methods. The concrete subclasses can also
define their unique qualities and behaviors.
1.5 Advantages of Abstraction

Abstraction offers various benefits for Java developers.
● First, it helps to minimize the complexity of a software system by focusing on the main
aspects and hiding unneeded details.
● Second, it supports code reusability by exposing a common set of features and
behaviors that may be reused by different objects.
● Third, it increases the maintainability of a software system by making it easier to modify
and extend the code.
1.6 Real-world Examples of Abstraction in Java
Abstraction is commonly used in Java programming to create multiple features and behaviors of
a software system. For example, the Java Collection Framework employs abstraction to provide
a set of standard interfaces and classes for handling collections of objects. The JDBC API
employs abstraction to provide a common set of interfaces for communicating with different
types of databases. The Servlet API employs abstraction to provide a common set of interfaces
and classes for constructing web apps.
1.7 Best Practices for Implementing Abstraction
The underlying principle of abstraction in object-oriented programming (OOP) enables
programmers to design large systems by dissembling them into simpler, more manageable
components. When it comes to generating abstraction in Java, there are some best practices
that developers should follow to guarantee that their code is efficient, maintainable, and easy to
comprehend.
Identify Objects and their Attributes
The first step in implementing abstraction is to find the objects in your system and their
properties. Attributes are the traits that define an item, such as its size, color, or shape. By
identifying the objects and their attributes, you can determine what behaviors are needed to
manipulate these items.
Determine Object Behaviors
Once you have located the objects and their attributes, the following step is to establish the
behaviors that these objects need to do. These behaviors should be focused on changing the
attributes of the objects and performing actions that are vital to the system.
Identify Common Object Behaviors
After identifying the actions needed for each object, you should look for common behaviors that
can be abstracted into a parent class or interface. This will allow you to reuse code and
construct a more efficient system.

Create Abstract Classes and Methods
Abstract classes and methods are an important aspect of implementing abstraction in Java.
Abstract classes are classes that cannot be instantiated and are used as a blueprint for
developing additional classes. Abstract methods, on the other hand, are methods that are
defined but not implemented in the abstract class. These methods must be implemented by the
child classes that take from the abstract class.
Implement Interfaces
Interfaces are another approach to constructing abstraction in Java. A combination of abstract
functions termed an interface is open for implementation by any class. Interfaces are used to
represent a common set of behaviors that can be implemented by other classes, allowing for
greater flexibility in the system.
Use Access Modifiers Wisely
When establishing abstraction in Java, it's vital to apply access modifiers judiciously. Access
modifiers govern the appearance of variables and methods in a class. By utilizing access
modifiers effectively, you can ensure that your code is secure and that each object only has
access to the data and methods that it requires.
1.8 Abstraction VS Encapsulation
Abstraction and Encapsulation are two essential ideas in Object-Oriented Programming (OOP),
especially in the Java programming language. While the two concepts may seem similar, they
serve different aims in software design. In this section, we will investigate the distinction
between Abstraction and Encapsulation in Java.
Abstraction is the process of hiding the complexity of a system and displaying only the relevant
elements to the user. Java's generic classes and interfaces are utilized to generate abstraction.
A class that has one or more abstract methods and cannot be instantiated is said to be abstract.
An abstract method is a method without an implementation, which means that any class that
extends the abstract class must supply an implementation for the abstract method.
On the other hand, Encapsulation is the process of hiding the internal intricacies of an item and
exposing only the relevant information to the outside world. The principle of encapsulation is
achieved by using access modifiers such as public, private, and protected. The public modifier
implies the field or method can be accessed from anywhere inside the program, while the
private modifier means it can only be accessed within the class.
The major distinction between Abstraction and Encapsulation is that Abstraction focuses on the
behavior of an object and its implementation details, whereas Encapsulation focuses on the
data and its safety from outside intervention. Abstraction is about defining the contract for the

behavior of an object, while Encapsulation is about safeguarding the data and enabling
controlled access to it.
To further grasp the distinction between Abstraction and Encapsulation, consider the following
example:
Suppose we have a class called BankAccount that represents a bank account. The
BankAccount class contains two fields: account number and amount. The class also includes
two methods: deposit() and withdraw(), which allow the user to place and withdraw money from
the account.
In this scenario, Abstraction would include specifying the behavior of the BankAccount class
without revealing its implementation specifics. We may achieve this by designing an abstract
class named Account that describes the deposit() and withdraw() methods as abstract methods.
Any class that extends the Account class would be needed to provide an implementation for
these methods.
Encapsulation, on the other hand, would mean safeguarding the data of the BankAccount class
from outside intervention. We may achieve this by keeping the account number and balance
fields private and giving getter and setter methods to access and alter them. This way, the data
of the BankAccount class is protected from being modified by outside classes.
1.9 Common Misconceptions About Abstraction
Abstraction is one of the key principles of Object-Oriented Programming (OOP), yet it is often
misinterpreted. In this essay, we will examine some frequent misconceptions concerning
abstraction in Java and provide clarity on these misunderstandings.
1. Abstraction is the same as Encapsulation
Abstraction and encapsulation are two different notions in OOP. Abstraction is about portraying
difficult real-world entities as simplified models in code, while encapsulation is about hiding the
internal implementation details of a class from the outside world. Encapsulation is accomplished
through access modifiers like private, protected, and public, whereas abstraction is achieved
using abstract classes and interfaces.
2. Abstraction is only for huge projects
Abstraction is a valuable strategy for projects of any size. Even tiny projects can benefit from
abstraction by making the code more understandable and easier to manage. Abstraction
enables the better organization of code and supports modularity, making it easier to maintain or
change the code without affecting the rest of the project.
3. Abstraction is only for skilled writers

Abstraction is not an approach that is limited to advanced programmers. It is a fundamental
notion that can be grasped by anyone with minimal knowledge of OOP. Abstraction is also not
just for writing code but also for comprehending it. By adopting abstraction, we can understand
complex processes more readily.
4. Abstraction is only used for polymorphism
Polymorphism is a key element of OOP, and abstraction is commonly employed to achieve it.
However, generalization is not restricted to polymorphism. It is also used for code reuse, making
it easier to store and update code, and for establishing hierarchies of classes that represent
real-world items.
5. Abstraction is always important
An abstraction is a great tool, but it is not always required. In some circumstances, it might lead
to needless complexity and make the code harder to understand. It is crucial to achieve a
balance between abstraction and ease and to only utilize abstraction when it is necessary.
2. Encapsulation in Oops concept
Introduction
Object-oriented programming is a paradigm in software development that is based on the
principles of encapsulation, inheritance, and polymorphism. One of the core ideas in
object-oriented computing is encapsulation. In this article, we will discuss the concept of
encapsulation and its importance in object-oriented programming.
2.1 What is encapsulation?

The method of encapsulation in Java involves shielding an object's implementation specifics
from the outside world. The idea behind encapsulation is to provide a simple interface to the
user while hiding the complexities of the object's internal workings. Encapsulation is achieved by
declaring the internal data and methods of the object as private and providing public methods to
access and manipulate the data.
2.2 Access Modifiers
In object-oriented programming, access modifiers are used to control the visibility and
accessibility of the data and methods of an object. There are three types of access modifiers in
most programming languages:
● Public: Public members are able to access any part of the program, including those
outside the class.
● Private: Private members are only accessible within the class where they are declared.
● Protected: Protected members are accessible within the class where they are declared
and any derived classes.
2.3 Why is encapsulation important?
Encapsulation is important for several reasons:
1. Data hiding: Encapsulation in Oops allows us to hide the internal data of an object,
preventing it from being modified by external entities. This ensures the integrity of the
object's data.

2. Modularity: Encapsulation promotes modularity by allowing us to separate the interface
of an object from its implementation. The code is now simpler to manage and update as
a result.
3. Abstraction: Encapsulation provides a level of abstraction by hiding the implementation
details of an object. This allows us to focus on the functionality of the object rather than
its implementation.
4. Security: Encapsulation improves security by preventing unauthorized access to the
internal data of an object. This ensures that the object's data is not modified or accessed
by malicious entities.
2.4 How does encapsulation work?
Encapsulation works by declaring the internal data and methods of an object as private, and
providing public methods to access and manipulate the data. The public methods are the only
means by which external entities can interact with the object. This ensures that the internal data
of the object remains hidden from the outside world.
Encapsulation example
Let's take an example of a class that represents a bank account. The internal data of the bank
account, such as the balance, should be kept private to prevent unauthorized access or
modification. The public methods of the class, such as deposit and withdrawal can be used to
manipulate the balance.
class BankAccount:
def init_(self, Initial_balance):
self.balance = initial balance
def deposit(self, amount):
self._ _balance +- amount
def withdraw(self, amount):
if self.balance - amount >= 0:
self.balance -= amount
else:
print ("Insufficient funds")
def get balance (self):
return self.balance
In this example, the balance of the bank account is declared as private using the double
underscore prefix. The public methods, deposit, withdraw, and get_balance, are used to
manipulate the balance. This ensures that the internal data of the bank account remains hidden
from the outside world.

3. Polymorphism: Understanding the
OOPs Concept in Java
Polymorphism in Java is a fundamental concept in object-oriented programming (OOP). It
allows programmers to design and create more flexible, reusable, and maintainable code by
providing a way to use a single method or object in different ways. In this article, we will explore
the different aspects of polymorphism in Java, its types, and examples.

3.1 What is Polymorphism?
Image explaining Polymorphism types
Polymorphism is derived from the Greek words "poly" meaning many, and "morph" meaning
forms. In OOP, polymorphism refers to the ability of an object or method to take on different
forms or behaviors. It enables the creation of code that can work with different data types or
objects, without the need to create separate code for each type.
Polymorphism is achieved in Java using two main techniques - method overloading and method
overriding. In method overloading, multiple methods with the same name but different
parameters are created. Method overriding involves creating a method in a subclass that has
the same name, return type, and parameters as a method in its superclass.
3.2 What are the types of Polymorphism?
Java supports static and dynamic polymorphism, two different types of polymorphism.
Static Polymorphism
Compile-time polymorphism or method overloading are other names for static polymorphism.
When a compiler determines which method to call at compile-time based on the arguments
passed to it, the compiler determines which method to call. It is used when the method
signatures are different, but the functionality remains the same.
Dynamic Polymorphism

Dynamic polymorphism is also known as run-time polymorphism or method overriding. It occurs
when the JVM determines which method to call at run-time based on the object that is being
referred to. It is used when the method signature is the same, but the functionality needs to be
changed.
Method Overloading
The process of generating numerous methods with the same name but different parameters is
known as method overloading. The compiler determines which method to call based on the
number, type, and order of arguments passed to it. It is used to provide different ways of calling
the same method with different inputs.
Method Overriding
Method overriding is the process of creating a method in a subclass that has the same name,
return type, and parameters as a method in its superclass. It is used to provide a specific
implementation of a method in the subclass while inheriting the other properties from its
superclass.
Abstract Classes and Interfaces
Abstract classes and interfaces are used to implement polymorphism in Java. An abstract class
is a class that cannot be instantiated, and it can have abstract methods that must be
implemented by its subclasses. An interface is a collection of abstract methods that must be
implemented by its implementing class.
3.3 Polymorphism Examples
Here are some examples of polymorphism in Java:
● Method overloading:
The same name has different parameters for the two methods.
public void print(int num){
System.out.printIn(num);
}
public void print(String str) {
System.out.printin(str);
}
● Method overriding:

Methods in a subclass that have the same name, return type, and parameters as methods in
their superclasses.
class Shape {
public void draw() {
System.out.printIn("Drawing a Shape");
}
}
class Circle extends Shape {
public void draw
3.4 What are the best practices for Polymorphism?
Java's powerful polymorphism object-oriented programming concept enables objects of various
classes to be treated as though they were objects of the same superclass. Polymorphism
makes code more flexible and reusable. Here are some best practices for using polymorphism
in Java:
1. Create a hierarchy of related classes using inheritance:
Inheritance is the foundation of polymorphism. By creating a superclass and one or more
subclasses that inherit from it, you can define a hierarchy of related classes that share common
characteristics. This allows you to write code that can work with any object in the hierarchy,
regardless of its specific type.
2. To define common behavior, use abstract classes and interfaces:
Abstract classes and interfaces are powerful tools for defining common behavior that can be
shared by multiple classes. By defining abstract methods or interface methods, you can ensure
that all classes that implement the abstract class or interface will provide the necessary
functionality.
3. Use method overriding to implement specific behavior:
The process by which a subclass provides a particular implementation of a method that is
already specified in its superclass is known as method overriding. This allows you to tailor the
behavior of each subclass to its specific needs while still treating all objects in the hierarchy as if
they were of a common type.
4. Use the instanceof operator to check object types:
You can ascertain an object's type at runtime with the instanceof operator. This can be useful
when you need to perform different actions based on the type of object you are working with.
5. Use the super keyword to call superclass methods:

The super keyword allows you to call methods in the superclass from within a subclass. This
can be useful when you need to modify the behavior of a superclass method in a subclass but
still want to maintain the original behavior of the superclass.
6. Use polymorphism to write flexible, reusable code:
The true power of polymorphism lies in its ability to write code that is flexible and reusable. By
writing code that can work with any object in a hierarchy, regardless of its specific type, you can
create code that is more robust and easier to maintain
4. Inheritance in Object-Oriented
Programming
Object-oriented programming (OOP) is a popular programming paradigm that employs objects
to represent and manipulate data. One of the fundamental concepts of OOP is inheritance,

which allows one class to inherit properties and methods from another. In this article, we will
investigate the concept of inheritance in Java and its various types.
4.1 Introduction to Inheritance
A class can derive or inherit properties and methods from another class using inheritance in
OOPS. The class that is being inherited from is called the progenitor class, base class, or
superclass. The class that inherits from the parent class is termed the child class, derived class,
or sub-class. Inheritance enables code reuse, reduces code redundancy, and promotes
modularity and flexibility in program design.
4.2 Types of Inheritance in Java
Java supports several forms of inheritance, including single inheritance, multilevel inheritance,
and hierarchical inheritance. However, Java does not support multiple inheritance or hybrid
inheritance, which are available in some other programming languages.
Single Inheritance
Single inheritance is the most common form of inheritance in Java, where a child class inherits
properties and methods from a single-parent class. The child class can add its properties and
methods or override the ones inherited from the parent class.
Multilevel Inheritance

Multilevel inheritance is a form of inheritance in Java, where a child class inherits properties and
methods from a parent class, which itself inherits properties and methods from its parent class.
In other words, there is a chain of inheritance that runs from the grandparent class to the parent
class to the child class.
Hierarchical Inheritance
Hierarchical inheritance is a form of inheritance in Java, where multiple child classes inherit
properties and methods from a single-parent class. In other words, there is a tree-like structure
of inheritance that runs from a single-parent class to multiple child classes.

Multiple Inheritance (Not supported in Java)
Multiple inheritances is a form of inheritance in some programming languages, where a child
class can inherit properties and methods from multiple parent classes. This can lead to code
complexity, conflicts, and ambiguity, which is why Java does not support multiple inheritances.
Hybrid Inheritance (Not supported in Java)
Hybrid inheritance is a form of inheritance in some programming languages, where a
combination of multiple inheritance and single inheritance is used. This can lead to even more
code complexity, conflicts, and ambiguity, which is why Java does not support hybrid
inheritance.
4.3 Syntax of Inheritance in Java
The syntax of inheritance in Java entails the use of the extends keyword to indicate that a child
class is inheriting from a parent class. The syntax is as follows:
class ParentClass {
//Properties and Methods
}
Class ChildClass extends ParetClass {
//Properties and Methods
}

4.4 The exceptional Keyword in Inheritance
In Java, the super keyword is used in inheritance to refer to the parent class. It is a reference
variable used to access the properties and methods of the parent class from within the child
class. The super keyword can be used to invoke the parent class's constructor, properties, and
methods.
One common use of the super keyword is to invoke the parent class's constructor from within
the child class's constructor. This is beneficial when the parent class has certain properties that
must be initialized before the child class can be created.
4.5 Method Overriding in Inheritance
Method overriding is a feature in the inheritance that enables a child class to provide its
implementation of a method that is already defined in the parent class. This enables the child
class to customize or extend the behavior of the inherited method according to its specific
requirements. To override a method, the offspring class must use the same method signature as
the parent class method, including the method name, return type, and parameters. The child
class can also use the @Override annotation to signify that it overrides a method from the
parent class.
4.6 The final Keyword in Inheritance
The final keyword in inheritance is used to prevent a class, method, or variable from being
overridden or modified by any offspring class. When a class is marked as final, it cannot be
extended by any other class. Similarly, when a method is marked as final, it cannot be
overridden by any child class, and when a variable is marked as final, its value cannot be
modified once it is initialized.
Using the final keyword in inheritance can help ensure that the critical functionality of a class or
method is not modified or broken by child classes that may not fully comprehend the
implications of their changes. Additionally, marking classes or methods as final can help
optimize code execution since the compiler can make certain assertions about their behavior
that do not need to be checked at runtime.
4.7 The abstract Keyword in Inheritance
The abstract keyword in inheritance is used to define abstract classes and methods. An abstract
class is a class that cannot be instantiated, indicating that you cannot create objects of the
abstract class directly. Instead, you must construct a subclass that extends the abstract class
and provides its implementation for any abstract methods defined in the abstract class.

An abstract method is a method that is declared in an abstract class but does not provide an
implementation. Instead, the implementation of the abstract method is left to the subclasses that
extend the abstract class. Any class that extends an abstract class must provide an
implementation for all of its abstract methods, or it must also be declared as an abstract class.
Using the abstract keyword in inheritance can help ensure that certain behavior or functionality
is implemented consistently across all subclasses, while still allowing for customization and
extension through the implementation of abstract methods in each subclass. Additionally,
abstract classes can provide a level of abstraction that makes code more flexible and simpler to
maintain.
4.8 When to Use Inheritance?
Inheritance is a powerful concept in object-oriented programming that enables you to create
new classes that are built upon existing classes, inheriting their properties and behaviors. Here
are some common situations in which inheritance can be useful:
Code Reusability:
Inheritance allows you to reuse code from existing classes, reducing the quantity of code you
need to write and increasing the efficiency of your development process.
Consistency:
Inheritance can help you maintain consistency across your codebase by assuring that all
classes that inherit from a particular base class share certain properties and behaviors.
Extensibility:
Inheritance enables you to extend the functionality of existing classes by adding new properties
and behaviors to your subclass, without altering the original class.
Polymorphism:
Inheritance can facilitate polymorphism, which allows objects of distinct classes to be treated as
if they are of the same type.
However, it is crucial to use inheritance carefully, as overuse can lead to complex and
hard-to-maintain code. Inheritance should be used when there is a clear and logical relationship
between the base class and the subclass, and when it makes sense to use the existing
properties and behaviors of the base class. If the relationship is not apparent or the subclass
requires significant modification of the base class, other programming concepts, such as
composition or interfaces, may be more appropriate.

4.9 Best Practices for Using Inheritance
Here are some recommended practices for using inheritance in object-oriented programming:
Follow the "is-a" relationship:
Use inheritance only when there is an unambiguous "is-a" relationship between the base class
and the subclass. For example, a Cat class can inherit from an Animal class because a cat is an
animal, but a Car class should not inherit from a Vehicle class because a car is not a vehicle.
Keep it simple:
Avoid deep inheritance hierarchies and excessive complexity, as they can make the code
tougher to understand and maintain. Use inheritance to add or modify behavior as
required, but avoid adding unnecessary complexity.
Avoid duplication:
Don't duplicate functionality between the base class and the subclass. Instead, define common
functionality in the base class and utilize it in the subclass through inheritance.
Encapsulate implementation details:
Hide the implementation details of the base class from the subclass, and avoid accessing
protected or private members of the base class from the subclass unless necessary.
Use interfaces when appropriate:
When the relationship between classes is more about behavior than inheritance, use interfaces
instead of inheritance. This can make the code more flexible and simpler to maintain.
Consider the Liskov Substitution Principle:
Make sure that any subclass can be used instead of the base class without affecting the
correctness of the program. This means that the subclass should not alter the behavior of any
public methods in the base class.
By following these best practices, you can use inheritance effectively and create maintainable,
flexible, and extensible object-oriented code.

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