Abstract Class


An abstract class, in the field of technology and particularly in object-oriented programming, is a class that cannot be instantiated into an object and is designed to be subclassed by other classes. It typically includes at least one abstract method, which is declared but not implemented within the abstract class. Any class that inherits from an abstract class must implement its abstract methods.


The phonetic transcription of “Abstract Class” is /ˈæbˌstrækt klæs/.

Key Takeaways

  1. Abstract Class is a special type of class in Object Oriented Programming that cannot be instantiated. It is designed to be extended by other classes, and it often serves as a blueprint for those classes.
  2. Abstract Class can have abstract methods that do not have an implementation in the Abstract Class itself but must be implemented in any concrete(non-abstract) classes that derive from it. This feature serves to enforce a certain level of design and coding consistency across subclasses.
  3. Abstract Class can also contain concrete methods (methods with implementation) providing default behavior that can be leveraged or overridden by its subclasses. This makes it a powerful tool for reducing code redundancy and improving code maintainability in complex programming projects.


Abstract class is a crucial term in technology, particularly in the realm of object-oriented programming. It’s important because it provides a base, or blueprint, upon which other classes can be built. It defines a common interface and default behavior that can be inherited by multiple subclasses, promoting code reuse and reducing redundancy. An abstract class, as the name suggests, is abstract in nature – it can’t be instantiated directly but can be extended by other classes. Thus, its core importance lies in enabling developers to lay out a consistent, robust framework for complex codes, making the software more manageable, scalable, and maintainable. It stimulates reusability of code and polymorphism, two paramount concepts in programming.


An abstract class serves a fundamental purpose in object-oriented programming (OOP). It operates as a blueprint for other classes, prioritizing the concept of abstraction to hide the technical complexity of operations from users. Essentially, an abstract class outlines certain methods and variables that subclasses must have but does not fully implement their functionalities. The abstraction allows developers to build upon this set-up without delving into low level specifics, fostering efficiency when coding. Abstract classes are used when developers plan to design related classes that need to share some common features.

For example, an abstract class “animal” may predefine methods such as “eat” and “sleep”, which are common to subclasses such as a “dog” or a “cat”. However, it doesn’t specify how these actions are carried out. This is left to the individual subclasses to define, allowing for the variability that we see in different types of animals. Consequently, an abstract class provides a flexible structure for the similar characteristics of multiple classes while leaving the specific details open to adjustment.


1. Frameworks: Within various software frameworks and libraries, abstract classes are often used to provide a base level implementation of an interface, which can then be built upon by a developer. For example, in the .NET Framework, the `Stream` class is an abstract class that provides a common set of methods and properties that are shared by all stream classes, such as `FileStream`, `MemoryStream`, `NetworkStream`, etc.

2. Database Schema: In object-oriented databases, an abstract class can be used to define a database schema. For instance, you may have an abstract class called `Employee`, which includes fields such as `Name`, `Age`, `Salary`. You could thereby inherit this abstract class to create `FullTimeEmployee` and `PartTimeEmployee` classes, incorporating extra specifics relevant to each.

3. GUI Toolkits: In Graphical User Interface (GUI) toolkits, abstract classes can often be found. For example, in Java’s Swing Library, the `AbstractButton` is an abstract class from which all button-like components are derived: `JButton`, `JCheckbox`, `JMenuItem` and more. It provides a baseline that includes the concept of text, icons, and tool tips, without specifying how the button is being activated or rendered.In each of these real world cases, abstract classes are being used to define a basic level of functionality or structure that is common to a group of related classes. Other classes then inherit from these abstract classes to add more specific functionality or behavior. In this way, abstract classes provide a mechanism for code reuse, encapsulation, and abstraction.

Frequently Asked Questions(FAQ)

Q1: What is an Abstract Class in technology?

A1: An Abstract Class is a special type of class in object-oriented programming that cannot be instantiated. It’s used as a blueprint for other classes and always extends to other classes that provide the implementation of the abstract methods declared in it.

Q2: How is an Abstract Class different from a regular class?

A2: The key difference is that abstract classes cannot be instantiated into an object, and they typically contain one or more abstract methods. These are methods declared in an abstract class but do not have an implementation in the abstract class itself.**Q3: Can you use an Abstract Class directly?

A3: No, you cannot use an Abstract Class directly. It must be inherited by another class, known as a subclass. The subclass then provides the implementation for the abstract methods defined in the Abstract Class.

Q4: What is the purpose of an Abstract Class?

A4: The primary purpose of Abstract Classes is to serve as a base class for subclasses. By defining what is like ‘capturing common characteristics’, they allow you to design methods that can work with a broad array of related classes and objects.

Q5: How does an Abstract Class function?

A5: An Abstract Class functions as a template for other classes. The child classes that extend the Abstract Class can use the methods and fields defined in the Abstract Class but they need to provide the specific implementation for the methods marked as abstract in the Abstract Class.

Q6: Can you instantiate an Abstract Class?

A6: No, an Abstract Class cannot be instantiated. An object can only be created from non-abstract classes.

Q7: Can an Abstract Class have a constructor?

A7: Yes, an Abstract Class can have a constructor, and it is usually defined to initialize the data members of the class. However, since it cannot be instantiated, the constructor is called when an instance of a subclass is created.

Q8: In which programming languages are Abstract Classes commonly used?

A8: Abstract Classes are a key feature of many object-oriented programming languages, including Java, C#, C++, PHP, and Python.

Q9: Can an Abstract Class have implemented methods?

A9: Yes, an Abstract Class can have both abstract methods lacking their own implementation and regular methods with fully implemented functionality. However, if an Abstract Class contains at least one abstract method, the class itself must also be defined as abstract.

Q10: Can an Abstract Class include fields (attributes)?

A10: Yes, an Abstract Class can contain fields (also known as variables or attributes), and these fields can be set to any accessibility: private, protected, or public. The fields serve as variables that store values for an object to use.

Related Technology Terms

  • Polymorphism
  • Inheritance
  • Encapsulation
  • Method Overriding
  • Interface

Sources for More Information


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