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Polymorphism In OOPS: What is Polymorphism [Detailed Explanation]

Polymorphism in OOPs is inseparable and an essential concept of every object-oriented programming language. An object or reference basically can take multiple forms in different instances. As the word suggests, ‘poly’ means ‘many’ and ‘morph’ points at ‘forms’; thus, polymorphism as a whole would mean ‘a property of having many forms.’

The object-oriented programming language processes classes and objects by a single interface. It implements the concepts of function overloading, overriding, and virtual functions. Also, it is typically used for instrumenting inheritance in programming. 

Polymorphism is one of the significant OOPS concepts. Using Polymorphism, you can have various or multiple forms of objects, variables, or methods. There can be varied implementations of the same method as per the class’ need using Polymorphism.

The concept of polymorphism offers great scalability and boosts the code’s readability. You can define polymorphism to have your unique implementation for the same method within the Parent class. Generally, it can be obtained using inheritance which implies that the class must belong to the same hierarchy tree. Knowing more about Polymorphism implementation in the programming world and how you can access it using the class object is necessary.

It denotes an object’s/reference’ ability to adopt several forms in various instances. It uses the concept of function overriding, function overloading, and virtual functions.

Polymorphism is a property using which any message could be delivered to objects of multiple classes. Each object owns the tendency to respond appropriately based on the class properties.

It implies that polymorphism is the method in an OOP language that performs different things based on the class of the object that calls it. For instance example, $rectangle->area() will return the area of a rectangle, but $square->area() will return the area of a square. But $object->area() will have to calculate the area based on which class $object was called.

Why is polymorphism used?

The concept of polymorphism helps you to perform a single action in various ways. It helps you to define one interface and benefit from multiple implementations. The term to explain polymorphism is such that the word “poly” indicates many and “morphs” indicates forms. Hence, it implies many forms.

Polymorphism in Java is used for the following important reasons:

Code reusability: OOPS polymorphism allows using a single interface to represent a general action across multiple classes. This means common functionality can be defined in a superclass, and subclasses can override these methods to provide their specialized implementations. This reusability reduces redundant code and makes maintenance easier.

Flexibility and extensibility: You can add new classes that implement a common interface without modifying existing code through polymorphism. This facilitates scalability and allows for easy extension of functionality by introducing new classes that conform to the existing interface.

Abstraction: Polymorphism in Java enables the use of abstract classes or interfaces to define methods without specifying their implementation details. This abstraction allows for a higher level of generalization and helps design systems based on behaviors rather than specific implementations.

Simplification of code: Polymorphism can simplify code by allowing a single method to be used for multiple different objects. This makes the code more concise, readable, and maintainable.

Run-time binding (Dynamic Binding): OOPS polymorphism allows for dynamic binding of method calls at runtime. When a method is invoked on an object, the specific implementation to be executed is decided at runtime, considering the actual object type, not the declared type. This enables flexibility in program behavior during execution.

Polymorphic behavior: It allows for polymorphic behavior, meaning that different objects can respond to the same message differently based on their specific implementations. This facilitates the handling of diverse objects in a unified manner.

Benefits of Polymorphism in OOPS:

Polymorphism aids the developer in reusing the program codes. It suggests that the old codes and classes written once, confirmed, and executed can be reused when required. This saves a programmer’s time. Hence, these codes and associated classes may be relevant to other methods.

Only a single variable can be used for storing multiple data types like Float, Int, Long, Double, etc. It simplifies the process of searching and executing the types of variables the users utilize.

You can define polymorphism to simplify code debugging. It assists in maintaining and reducing the coupling among different functionalities.

Defining methods in a superclass and overriding them in subclasses provides a clear and organized structure that simplifies maintenance and debugging efforts.

It benefits programmers with the flexibility to write programs that uses just one method for several executions as required. This method can work inversely for various inputs based on the interface type.

One of the biggest benefits to explain polymorphism is that it allows the programming code to expand itself to use the previous program. Thus, it saves the developers’ effort and time.

The core theory of OOPs languages is also implemented for programming various forms of large execution of codes.

It allows for programming various forms of code execution and facilitates the development of flexible, extensible, and maintainable codebases.

The Polymorphism feature lets programming become more resourceful and faster for code development.

Developers can build upon existing code, resulting in more efficient development cycles.

It decreases coupling and maximizes reusability to code a readable program.

Emphasizing a modular and loosely coupled design helps create more readable, maintainable, and adaptable programs.

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Read: Polymorphism vs Inheritance

An Example of Polymorphism in OOPs

Polymorphism is the method in an object-oriented programming language that performs different things as per the object’s class, which calls it. With Polymorphism, a message is sent to multiple class objects, and every object responds appropriately according to the properties of the class. 

Following is the code that explains polymorphism clearly:

use warnings;
# Creating package class
package A;
# Creating Constructor
sub new
{
# shift will take package name
# and assign it to variable ‘class’
my $class = shift;
my $self = {
‘name’ => shift,
‘roll_no’ => shift
};
sub method
{
print(“This belongs to class A “);
}
};
package B;
# The @ISA array contains a list
# of that class’s parent classes, if any
my @ISA = (A);

submethod
{
print(“This belongs to class B”);
}
package main;
B->method();
A->method();

Output:

This belongs to class B

This belongs to class A

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Explanation

For the first output, the method() defined in class B overrides the definition inherited from class A and vice-versa for the second output. This property is useful in extending any pre-existing package’s functionality without rewriting the entire class’s entire definition. Thus, making the job easy for the programmer and the reason for being used widely.

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Important concepts about Polymorphism in OOPS:

What are the principles of Polymorphism in OOPS?

The dictionary definition of OOP polymorphism relates to the biology principle in which species or organisms can have several different stages or forms. This principle can be applied to object-oriented programming and languages such as Java.

In programming, this indicates different classes can have methods with the same name but different implementations. When a method is called on an object, the specific implementation associated with that object’s class is executed. 

This concept helps create more flexible and reusable code by allowing different objects to be handled through a unified interface, similar to how various life forms can share common characteristics or stages in biology. In languages like Java, polymorphism is a fundamental feature that enables code to work with different objects in a uniform way, enhancing flexibility and extensibility.

 What is overloading and overriding in Polymorphism?

In OOP polymorphism, overloading happens when two or more methods in one class share the same method name but with unique parameters. It happens when two methods share the same method name and parameters. These are the two common methods for overloading and overriding Polymorphism in the parent and child classes.

  • Method overloading: This occurs within a single class when multiple methods have the same name but differ in their parameters (either in the number of parameters or their types). For instance, a class might have two methods both named calculate, one accepting two integers and another accepting two doubles. 

The compiler differentiates between these methods based on the parameters provided when calling the calculate method. Overloading allows a class to perform similar tasks using different parameter inputs, enhancing code readability and usability.

  • Method overriding: This occurs when a method in a subclass has the same name, return type, and parameters as a method in its superclass. The subclass provides its implementation for that method. This feature allows a subclass to provide a specific implementation of a method already defined in its superclass. The method in the subclass overrides the method’s behavior in the superclass when the subclass object is used.

What are compile-time and runtime in Polymorphism?

Compile time is when the programming code (like C, C#, Java, Python) is transformed into the machine code i.e. binary code.

During compile time, the code is checked for syntax errors, and if the syntax is correct, the compiler generates an executable file or bytecode (in languages like Java). The compiler also performs various optimizations to enhance the performance of the resulting program.

The output of the compile time is an executable file (in the case of compiled languages like C or C++) or bytecode (in the case of languages like Java) that contains instructions the computer’s processor can understand.

Runtime is when a program is executing and usually happens after compile time.
During runtime, the computer’s processor executes the instructions in the compiled program or bytecode. It involves memory allocation, variable assignments, method calls, and any other action specified by the program’s logic.

The output of the runtime phase is the actual behavior or results produced by the executed program based on the operations specified in the source code.

Which type of function shows Polymorphism?

Compile time polymorphism is obtained by operator overloading or function overloading. Function overloading is when there are multiple functions with similar names.
To elaborate further, function overloading occurs when multiple functions within the same scope (class or namespace) have the same name but differ in their parameters (number or types of parameters). These functions may perform similar or related tasks but with different parameter inputs.

If varied parameters are used, then these functions are said to be overloaded.
Operator overloading allows operators (like +, -, *, /, etc.) to be redefined for user-defined types. It enables the use of operators with custom objects or types by specifying their behavior through specially defined functions.

What is a method in OOP?

The method in polymorphism explains that it is a programmed process that is defined as part of a class and incorporated into any object of the particular class. A class and an object can have multiple methods.

Methods in a class: A class serves as a blueprint or template to create objects. Methods defined within a class encapsulate the behaviors or functionalities associated with that class. These methods describe what an object of that class can do or how it can interact with other objects or the outside world.

Methods can perform various operations, such as modifying the object’s state (changing its attributes), performing calculations, interacting with other objects, or providing information about the object.

Methods in an object: When an object is created based on a class, it inherits all the methods defined in that class. These methods can be invoked or called on the object to perform specific actions associated with that object.

Each object maintains its own data set, and the methods define how that data can be accessed or manipulated for that specific instance of the class.

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Types of Polymorphism in Oops

In Object-Oriented Programming (OOPS) language, there are two types of polymorphism as below:

  1. Static Binding (or Compile time) Polymorphism, e.g., Method Overloading
  2. Dynamic Binding (or Runtime) Polymorphism, e.g., Method overriding

Source

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  1. Compile Time or Static Polymorphism

With Method Overloading, static polymorphism is achieved in Object-Oriented Programming languages that allow the programmer to implement various methods. The names they use can be the same, but their parameters are different.

In OOPS, you can attain compile-time polymorphism using method overloading. Java recognized which method to call after checking the corresponding method signature. In the method overloading polymorphism concept, there can be the same method name but a different number of arguments and the return type to execute this. In a nutshell, when the object is limited to its functionality, it is called compile time polymorphism.

In OOPS, you can attain compile-time polymorphism using method overloading. Java recognized which method to call after checking the corresponding method signature. In the method overloading polymorphism concept, there can be the same method name but a different number of arguments and the return type to execute this. In a nutshell, when the object is limited to its functionality, it is called compile time polymorphism.

Certain conditions are conducive to static polymorphism as below:

  •       Types of All Parameters should be different.
  •       The sequence of the Parameters can be different.
  •       The number of parameters of one method should differ from the other method.

In the static binding polymorphism, the matching type and number of arguments invoke the overloaded functions. 

  • As all of this information is available during the compile time, the compiler selects the appropriate function. 
  • The function overloading does it, and operator overloading is also termed as static binding or early binding.

Program

class A                                  //  base class

{

int a;

public:

void display()

{

cout<< “Class A “;

}

};

class B: public A                       //  derived class

{

int b;

public:

void display()

{

cout<<“Class B”;

}

};

In the above program, the display() function prototype is the same in both the base and derived classes. Therefore, static binding cannot be applied here. This program would run best at the run time with an appropriate selection of functions.

  • During the run time, the language’s compiler identifies various methods by identifying signatures of those methods.
  • The compiler first identifies the method signature and decides the method for a specific method call during program compilation.  
  • The execution for Compile time Polymorphism is much faster but the process is not so flexible. 

Also Read: OOPS Interview Questions

Runtime or Dynamic Polymorphism

In the Dynamic Polymorphism, a call to a single overridden method is solved during a program’s runtime. Method overriding is one of the prominent examples of Runtime Polymorphism. In this process, the overriding is done through pointers and virtual functions.

Run time polymorphism is alternatively called dynamic polymorphism. This is because a method to call is decided at run time but not compiler time. Since both methods will own the same signature and could be called using any one of the class objects, the compile-time compiler doesn’t know about this; it can only be identified during runtime.

Run time polymorphism is alternatively called dynamic polymorphism. This is because a method to call is decided at run time but not compiler time. Since both methods will own the same signature and could be called using any one of the class objects, the compile-time compiler doesn’t know about this; it can only be identified during runtime.

  • In Method Overriding, a single method is declared in a sub-class present in a parent class. The child class gains a method for implementation.
  • During Runtime Polymorphism, the class offers the specification of its own to another inherited method. This transfer between methods is achieved without modifying the parent class object codes.

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Important points to note about the Polymorphism concept:

  • It should have the same name, same return type, and same parameters (order, type, and length).

This ensures that the overridden method is a proper replacement for the method in the superclass.

  • It can’t override a method that is declared static or final.

A static method belongs to the class, not to instances, and a final method cannot be modified or overridden in subclasses.

  • It can’t have a more restrictive access modifier.

For instance, if the superclass method is declared as public, the overriding method in the subclass cannot be private or protected, as this would restrict access more than the superclass allows.

  • It may have a less restrictive access modifier.

If the superclass method is, for example, protected, the subclass method can be declared as public. This rule enables the subclass method to broaden the scope of visibility compared to the superclass method.

  • It should not throw a new or wider checked exception.

If the superclass method throws a particular checked exception, the overridden method in the subclass can throw the same type of exception or narrower exceptions. However, it should refrain from introducing broader exceptions or entirely new types of checked exceptions.

  • It might throw fewer, narrower, or no checked exceptions.

These rules ensure that the subclass method doesn’t broaden the exceptions thrown beyond what the superclass method allows. Instead, it can narrow down the exceptions or not throw any checked exceptions, maintaining compatibility and flexibility in exception handling.

The overriding method of polymorphism explains that it can throw any unchecked exception, irrespective of whether the overridden method states the exception.

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Types of Polymorphism in Oops

In Object-Oriented Programming (OOPS) language, there are two types of polymorphism as below:

  1. Static Binding (or Compile time) Polymorphism, e.g., Method Overloading
  2. Dynamic Binding (or Runtime) Polymorphism, e.g., Method overriding

Source

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1. Compile Time or Static Polymorphism

With Method Overloading, static polymorphism is achieved in Object-Oriented Programming languages that allow the programmer to implement various methods. The names they use can be the same, but their parameters are different. Certain conditions are conducive for static polymorphism as below:

  •       Types of All Parameters should be different.
  •       The sequence of the Parameters can be different.
  •       The number of parameters of one method should differ from the other method.

In the static binding polymorphism, the matching type and number of arguments invoke the overloaded functions. 

  • As all of this information is available during the compile time, the compiler selects the appropriate function. 
  • The function overloading does it, and operator overloading is also termed as static binding or early binding.

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Program

class A                                  //  base class

{

int a;

public:

void display()

{

cout<< “Class A “;

}

};

class B: public A                       //  derived class

{

int b;

public:

void display()

{

cout<<“Class B”;

}

};

In the above program, the display() function prototype is the same in both the base and derived classes. Therefore, static binding cannot be applied here. This program would run best at the run time with an appropriate selection of functions.

  • During the run time, the language’s compiler identifies various methods by identifying signatures of those methods.
  • The compiler first identifies the method signature and decides the method for a specific method call during program compilation.  
  • The execution for Compile time Polymorphism is much faster but the process is not so flexible. 

Also Read: OOPS Interview Questions

Runtime or Dynamic Polymorphism

In the Dynamic Polymorphism, a call to a single overridden method is solved during a program’s runtime. Method overriding is one of the prominent examples of Runtime Polymorphism. In this process, the overriding is done through pointers and virtual functions.

  • In Method Overriding, a single method is declared in a sub-class present in a parent class. The child class gains a method for implementation.
  • During Runtime Polymorphism, the class offers the specification of its own to another inherited method. This transfer between methods is achieved without modifying the parent class object codes.

Program

 #include <iostream>    

using namespace std;    

class Animal {                                          //  base class  

    public:    

    string color = “Brown”;      

};     

class Dog: public Animal                       // inheriting Animal class.  

{      

 public:    

    string color = “Green”;      

};    

int main(void) {    

     Animal d= Dog();      

    cout<<d.color;     

}    

Output:

Brown 

  • In the Run time polymorphism, the object’s method is invoked at the run time instead of compile time. 
  • It is made possible by method overriding, which is also coined as dynamic binding or late binding. 
  • The process of dynamic polymorphism is comparatively slower but flexible than compile-time polymorphism.

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Differences B/W Compile-Time and Run-Time Polymorphism 

  Compile-Time Polymorphism Run-Time Polymorphism
Invoking of Function The function is invoked at the compile time. The function is invoked at the run time.
Common Terms It is known as overloading, early binding, and static binding. It is known as overriding, late binding, and dynamic binding.
Method Name and Parameters In Overloading, more than one method has the same name but with a different number or type of parameters. In Overriding, more than one method has the same name, number, and type of parameters.
Carriers It is achieved with function and operator overloading. It is achieved with virtual functions and pointers.
Execution Time It executes faster than run-time polymorphism at the compile time. It executes slower than compile-time polymorphism at the run time.
Flexibility It is less flexible as everything executes at the compile time. It is more flexible as everything executes at the run time.

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Java Inheritance and Polymorphism

In Java, inheritance and polymorphism are fundamental concepts that play a crucial role in object-oriented programming (OOP).

Inheritance:

Java supports inheritance, allowing one class (subclass or child class) to inherit attributes and behaviors (methods) from another class (superclass or parent class).

 

Syntax: class Subclass extends Superclass { … }

 

The subclass inherits the properties and methods of the superclass and can also have its own additional properties and methods.

 

It promotes code reuse and establishes an “is-a” relationship between classes, where a subclass “is a” type of its superclass.

 

Example:

 

// Superclass

class Animal {

public void makeSound() {

System.out.println(“Some sound”);

}

}

 

// Subclass inheriting from Animal

class Tiger extends Animal {

public void wagTail() {

System.out.println(“Pouncing”);

}

}

Polymorphism:

Polymorphism in Java allows objects belonging to different classes through method overriding to be treated as objects of a common superclass. It enables code to work with objects of various types using a shared interface, allowing for flexibility and extensibility. Polymorphism is attained via method overriding, wherein a derived class offers its own customized implementation for a method already defined in its parent class.

Example:

class Animal {

public void makeSound() {

System.out.println(“Some sound”);

}

}

 

class Tiger extends Animal {

@Override

public void makeSound() {

System.out.println(“Roar!”);

}

}

Here, if you have an Animal reference pointing to a Tiger object, calling the makeSound() method will execute the overridden method specific to the Tiger class at runtime, demonstrating polymorphic behavior.

Final Words

Polymorphism is the must learn concepts of OOPs as it offers several advantages while programming. With Polymorphism, the user can remodel the tested classes and codes. It is useful in extending the programming by itself. It also allows the user to store multiple different type variables such as double, Float, Int, or Long in a single variable to make it simpler to search and implement them. 

If you’re interested to learn more about OOPs, full-stack software development, check out upGrad & IIIT-B’s PG Diploma in Full-stack Software Development which is designed for working professionals and offers 500+ hours of rigorous training, 9+ projects and assignments, IIIT-B Alumni status, practical hands-on capstone projects & job assistance with top firms.

What is an object in Object-Oriented Programming (OOP)?

In object-oriented programming, the concept of an object is the primary aspect that developers think of while designing a program. An object is essentially the unit of code that is derived eventually from this process. Every object is correlated to a generic class of the object. Many generic classes are defined in the library so that each corresponding object of the class can share the specific class features, and developers can reuse the definition of the class while writing the code. So, each object is like an instance of a particular class or subclass. It shares the same model, features, properties, methods, procedures, and variables.

How is an object different from a class?

A class can be considered as a template or blueprint from which you can create objects. Objects are instances of a class that executes in the machine. Objects are real-world physical entities, whereas a class is a logical collection of similar objects. Developers can create as many objects as needed, but class is declared only once. Class does not occupy any memory when it is created, whereas memory is allocated as soon as an object is created. Objects can be declared or created in many ways using different keywords (based on the programming language). But class can be declared and defined in one way only.

What are the essential features of object-oriented programming?

There are five essential or key features of object-oriented programming – classes and objects, inheritance, polymorphism, data abstraction, and encapsulation. Classes are datatypes defined by the users and form the primary building blocks of object-oriented programming. Objects are real-life entities that are instances of a particular class. Inheritance is the ability of one class to inherit the properties of another base class. Polymorphism facilitates using the same function with different aliases. Encapsulation and abstraction enable the simplicity of coding for developers where they only interact with a subset of an object's overall attributes, i.e., only what is essentially required.

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