Polymorphism programming

In the realm of computer science, the concept of polymorphism is pivotal to both the understanding and development of efficient, adaptable software. As one delves into the world of programming, the significance of polymorphism becomes increasingly apparent. This article aims to provide a comprehensive introduction to polymorphism programming, exploring its definition and essence, the role it plays in object-oriented and functional programming, and its benefits and drawbacks. The article begins with a clear polymorphism definition in programming and highlights its importance in computer science. It then moves on to dissect the intricacies of polymorphism in object-oriented programming, using an easily understandable example. Following the exploration of object-oriented polymorphism, the advantages and disadvantages are examined, focusing on code reusability, flexibility, and the potential complexity and performance issues that may arise with its implementation. Finally, the article delves into functional programming polymorphism, providing a closer look at its implementation in various functional programming languages and common examples and applications. Throughout this in-depth analysis, the reader will gain a solid understanding of polymorphism as a core concept in computer science.

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Table of contents

    Polymorphism Programming: Definition

    Polymorphism is a programming concept that enables a single function, method or operator to work with multiple types or objects of different classes. It increases the flexibility and reusability of code by allowing objects of different classes to be treated as objects of a common superclass.

    Importance of Polymorphism in Computer Science

    Polymorphism plays a crucial role in computer science and programming. Some benefits of using polymorphism include:
    • Reusable code: Polymorphism allows developers to write one function or method that can handle different data types, resulting in less duplicate code.
    • Extensibility: Polymorphism makes it easier to extend existing functionality and add new features by simply adding a new class or method.
    • Abstraction: Polymorphism enables developers to design interfaces between components apart from their specific implementations, allowing for loose coupling and high cohesion in software systems.
    • Maintainability: Code that uses polymorphism is often more readable and easier to modify, as developers can focus on the high-level design without worrying about the details of each specific data type or class.

    Polymorphism in Object Oriented Programming

    Polymorphism is an essential feature of object-oriented programming (OOP) languages like Java, C++, and Python. In OOP, polymorphism can be achieved through various mechanisms:
    • Subtype polymorphism (also known as inheritance-based polymorphism): Allows a subclass to inherit methods and properties from a superclass, so methods of the superclass can be called on objects of the subclass.
    • Method overloading: Allows defining multiple methods with the same name but different parameter lists in a class. The appropriate method is chosen for a specific object based on the number and types of arguments passed to the method.
    • Method overriding: Enables a subclass to provide a new implementation of a method that is already defined in its superclass, effectively replacing the inherited method with a new one that is tailored to the subclass.
    • Operator overloading: Allows the same operator to have different actions depending on the types of its operands, as seen in programming languages like C++ and Python.

    Example of Polymorphism in Object Oriented Programming

    Let's consider a simple example of polymorphism in a Java program that deals with shapes. We start by defining an abstract class 'Shape' with an abstract method 'area()' that calculates the area of the shape:

    abstract class Shape {
      abstract double area();

    Now we create two subclasses, 'Circle' and 'Rectangle', which inherit from the 'Shape' class and provide their own implementations for the 'area()' method:

    class Circle extends Shape {
      double radius;
      Circle(double radius) {
        this.radius = radius;
      double area() {
        return Math.PI * radius * radius;
    class Rectangle extends Shape {
      double width, height;
      Rectangle(double width, double height) {
        this.width = width;
        this.height = height;
      double area() {
        return width * height;

    Finally, we can create an array of 'Shape' objects, fill it with 'Circle' and 'Rectangle' objects, and then calculate the total area of all shapes using polymorphism:

    public class Main {
      public static void main(String[] args) {
        Shape[] shapes = new Shape[3];
        shapes[0] = new Circle(1.0);
        shapes[1] = new Rectangle(2.0, 3.0);
        shapes[2] = new Circle(2.5);
        double totalArea = 0.0;
        for (Shape shape : shapes) {
          totalArea += shape.area(); // polymorphic method call
        System.out.println("Total area of all shapes: " + totalArea);

    This example illustrates the power of polymorphism: we can treat 'Circle' and 'Rectangle' objects as their superclass 'Shape' and call the 'area()' method to calculate the total area without maintaining separate logic for each shape type.

    Advantages and Disadvantages of Polymorphism in Object-Oriented Programming

    Polymorphism offers various advantages when implemented in object-oriented programming. These benefits include code reusability and flexibility, improved maintainability, support for inheritance and abstraction, and reduced coupling between components.

    Code Reusability and Flexibility

    Polymorphism promotes code reusability and flexibility in several ways:
    • With method overloading, you can have multiple methods with the same name but different parameter lists, which reduces the need to create multiple functions for similar tasks.
    • Method overriding allows a subclass to modify or enhance the functionality of its superclass without duplicating the code of the superclass, cutting down redundancy and improving the adaptability of the system.
    • Polymorphism enables you to create generic functions or classes that can work with multiple data types, allowing you to develop code that can be reused with various types of objects.
    • Operator overloading enables you to extend the semantics of standard operators, leading to more readable and compact code that behaves consistently with user-defined types.

    Drawbacks of Polymorphism

    Despite the many benefits, there are some drawbacks to using polymorphism in your programming projects. These drawbacks primarily involve potential complexity and performance issues.

    Potential Complexity and Performance Issues

    Polymorphism can lead to some complexity and performance concerns:
    • Increased code complexity: While polymorphism can make code more concise, it can also introduce an increased level of complexity due to the multiple layers of inheritance, method overloading, and operator overloading. Programmers may need to invest extra time and effort in understanding and managing these intricate relationships between classes and objects.
    • Performance overhead: Polymorphism often relies on indirect function calls using function pointers or virtual tables, which can introduce some performance overhead compared to direct function calls. This could be a concern in performance-sensitive applications or environments with limited resources, such as embedded systems.
    • Type system complexity: Languages that support polymorphism often have more complex type systems with features like subtyping and generics. This can make the learning curve steeper for newcomers, and can lead to an increased likelihood of type-related errors during development.
    • Debugging challenges: Debugging polymorphic code can be more challenging, as the dynamic dispatch used in polymorphism can make it harder to trace the exact method or function that is being executed at runtime. This can complicate the process of identifying and fixing issues in the codebase.

    In conclusion, while polymorphism offers several valuable benefits for code reusability, flexibility and maintainability, it also introduces some potential complexity and performance concerns. It is essential for developers to strike a balance and make informed decisions when employing polymorphism in their projects.

    Functional Programming Polymorphism: A Closer Look

    Functional programming languages, like Haskell, Lisp and ML, also support polymorphism, albeit with a different approach than object-oriented programming languages. In functional programming, polymorphism is generally achieved through parametric and ad-hoc polymorphism.

    Parametric Polymorphism

    Parametric polymorphism allows a function or a data type to be written generically so that it works uniformly with any desired type. One of the main characteristics of parametric polymorphism is its ability to abstract over types, meaning that the same code can be reused for multiple types. Haskell's Type Classes and ML's Functors are examples of mechanisms that enable parametric polymorphism in functional programming languages. Some benefits of parametric polymorphism include:
    • Code reuse: Parametric polymorphism minimises code duplication by enabling a single, generic function to work with multiple types.
    • Type safety: Functions that use parametric polymorphism can provide strong type safety, as the compiler checks consistency with the provided types.
    • Increased expressiveness: Using generic functions, developers can express more diverse and complex relationships between types, leading to more expressive and powerful code.
    • Performance benefits: Due to type inference and type specialisation, parametric polymorphism can sometimes offer performance improvements over other forms of polymorphism, since it can lead to more efficient compilation or optimisation strategies.

    Ad-Hoc Polymorphism

    Ad-hoc polymorphism, also known as overloading, refers to the ability to define multiple functions with the same name but different types. This allows a single function name to have various implementations based on the types of its arguments. The actual function invoked is determined during compilation based on the type of its input(s). Common examples of ad-hoc polymorphism include operator overloading and function overloading. Key features of ad-hoc polymorphism include:
    • Consistent syntax: Ad-hoc polymorphism allows the use of the same syntax to represent operations on different types, leading to more uniform and concise code.
    • Function overloading: Enables multiple functions with the same name but different type signatures to be defined, reducing the need for different function names for similar tasks.
    • Operator overloading: Allows operators to have different implementations depending on the types of their operands, increasing the readability and expressiveness of code by using familiar operators with user-defined types.
    • Flexibility: Ad-hoc polymorphism provides developers with the flexibility to design how specific functions should behave depending on the given input types, allowing fine-tuned and customised behaviour for different use cases.

    Common Examples and Applications

    Functional programming languages offer various ways to incorporate polymorphism, allowing a wide range of applications. Let's take a look at some specific examples in Haskell.

    Parametric Polymorphism Example: In Haskell, the 'map' function is a polymorphic example that works with lists of any type. Here's the type signature of 'map' and an example of its usage:

    map :: (a -> b) -> [a] -> [b]
    double x = x * 2
    result = map double [1, 2, 3, 4]
    -- result will be [2, 4, 6, 8]

    This example demonstrates how 'map' can be applied to different types. The 'double' function multiplies each element in the list by 2, and 'map' applies 'double' to a list of integers, resulting in a new list of doubled integers.

    Ad-Hoc Polymorphism Example: A common example of ad-hoc polymorphism in Haskell is the use of the '==' operator for equality comparison. The '==' operator can work with various types, thanks to Haskell's type classes. Here's a simple example of using the '==' operator with different types:

    isEqualInt = 42 == 42
    isEqualDouble = 3.14 == 3.14
    isEqualChar = 'a' == 'a'
    isEqualString = "hello" == "hello"
    -- All of these comparisons will return True

    This example illustrates how the '==' operator can be used with integers, floating-point numbers, characters, and strings, providing a uniform syntax for checking equality, regardless of the types involved.

    These examples highlight the various ways polymorphism can be incorporated into functional programming languages, promoting code reusability, expressiveness, and overall modularity in program structure.

    Polymorphism programming - Key takeaways

    • Polymorphism definition programming: A concept that enables a single function, method, or operator to work with multiple types or objects of different classes, increasing flexibility and reusability of code.

    • Polymorphism in object-oriented programming: Achieved through mechanisms such as subtype polymorphism, method overloading, method overriding, and operator overloading.

    • Example of polymorphism in object-oriented programming: A Java program dealing with shapes using an abstract class 'Shape' and subclasses 'Circle' and 'Rectangle' with their own implementation of an 'area()' method.

    • Advantages and disadvantages of polymorphism in object-oriented programming: Benefits include code reusability, flexibility, and maintainability, while drawbacks involve potential complexity and performance issues.

    • Functional programming polymorphism: Uses parametric and ad-hoc polymorphism, with examples in functional programming languages like Haskell.

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    Frequently Asked Questions about Polymorphism programming
    What is polymorphism in programming?
    Polymorphism in programming is a concept that allows objects of different classes to be treated as objects of a common superclass. It enables a single function or method to operate on multiple types, thereby providing flexibility and reusability in code. This enhances code readability and reduces complexity, as a single interface can handle various implementations.
    What is polymorphism in object-oriented programming?
    Polymorphism in object-oriented programming is a concept which allows objects of different classes to be treated as if they were objects of a common superclass. This enables a single function or method to operate on multiple types, allowing for cleaner, more reusable code. Polymorphism promotes flexibility and extensibility, as new classes can be added without modifying existing functions or methods that interact with the superclass.
    How does object-oriented programming support the concept of polymorphism?
    Object-oriented programming (OOP) supports the concept of polymorphism by allowing objects of different classes to be treated as objects of a common superclass. This is achieved through inheritance, where a derived class can inherit properties and methods from a base class, and can also override or extend them. It enables a single interface or method to work with different data types or objects, providing flexibility and code reusability in the programme.
    Why is polymorphism important in object-oriented programming?
    Polymorphism is important in object-oriented programming because it enables a single interface to represent different types of objects, promoting code reusability and flexibility. With polymorphism, the same behaviour or function can be applied to distinct classes, allowing a programmer to handle a variety of objects with consistent methods. Furthermore, it enhances the extensibility of a program, making it easier to add or modify components without disrupting existing code. Overall, polymorphism contributes to a more robust and maintainable software design.
    What is polymorphism in functional programming?
    In functional programming, polymorphism refers to the ability of a function to operate on different data types or take generic parameters, enabling code reusability and flexibility. This is often achieved through higher-order functions, parametric polymorphism, or type classes. Polymorphic functions can adapt their behaviour based on the input data, leading to more concise and maintainable code.

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