Abstract Class in Java: A Beginner’s Guide

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Abstract class in Java is an essential components of Object-Oriented Programming (OOP) that facilitate the creation of blueprints for other classes while providing a mechanism to enforce the structure of derived classes. They serve as a foundation for building class hierarchies and promoting code reusability and abstraction within Java programming.

Abstract Class in Java

What is an Abstract Class?

An abstract class in Java is a class that cannot be instantiated on its own and serves as a blueprint for other classes to inherit from. It may contain both abstract and concrete methods, along with fields, constructors, and other elements typical of regular classes. However, it’s important to note that an abstract class may have abstract methods (methods without a body), which are intended to be implemented by its subclasses.

Key Characteristics of Abstract Classes

  1. Cannot be Instantiated: Abstract classes cannot be instantiated directly, meaning you cannot create objects of an abstract class using the ‘new’ keyword.
  2. May Contain Abstract Methods: Abstract classes can have abstract methods, which provide a structure that derived classes must implement. These methods are declared using the ‘abstract’ keyword and lack an implementation within the abstract class itself.
  3. May Contain Concrete Methods: They can also include concrete methods (methods with an implementation) that can be directly used by subclasses.

Example of an Abstract Class in Java

abstract class AbstractExample{
    protected String name;

    public AbstractExample(String name) {
        this.name = name;
    }

    // Abstract method to getExample
    public abstract double getExample();

    // Concrete method to retrieve color
    public String getName() {
        return name;
    }
}

In this example:

  • AbstractExample is an abstract class that contains an abstract method getExample() and a concrete method getName().
  • The abstract method getExample() is intended to be implemented by subclasses to get related examples.

Usage and Benefits of Abstract Classes

  1. Code Reusability: Abstract classes facilitate reusability by providing a blueprint for derived classes, and reducing redundant code by defining common methods and attributes.
  2. Abstraction: They allow for abstract methods, enabling the definition of methods without implementation, thus enforcing specific behaviors in subclasses.
  3. Polymorphism: Abstract classes contribute to polymorphism, where objects of derived classes can be treated as objects of the abstract class, allowing for flexibility in programming.

Abstract classes in Java are pivotal elements in designing class hierarchies and promoting code abstraction and reusability. They act as templates for creating related classes and serve as a foundation for implementing common behaviors while enforcing specific methods to be defined in subclasses.

See Also

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