Java Abstraction

Abstraction is a fundamental concept in object-oriented programming (OOP) that allows us to create models of real-world objects with a high degree of complexity. It enables us to define the essential features of an object, while hiding the details of its implementation from the user.

In Java, abstraction is achieved through the use of abstract classes and interfaces. An abstract class is a class that cannot be instantiated, but can be subclassed by other classes. It may contain abstract methods, which are declared without an implementation and must be implemented by the subclass. Abstract classes can also contain non-abstract methods with an implementation.

An interface is a collection of abstract methods and constants. It defines a contract for classes to follow, specifying the methods that must be implemented and the constants that must be provided. Classes can implement one or more interfaces to inherit their abstract methods.

Here's an example of an abstract class and an interface in Java:

abstract class Shape {
    private String color;

    public Shape(String color) {
        this.color = color;

    public String getColor() {
        return color;

    public abstract double getArea();

interface Drawable {
    void draw();

In this example, Shape is an abstract class that contains a private variable color and a constructor that initializes it. It also contains a non-abstract method getColor() that returns the color of the shape, and an abstract method getArea() that must be implemented by any subclass of Shape.

The Drawable interface contains a single method draw(), which must be implemented by any class that implements the interface.

Here's an example of a subclass of Shape that implements its abstract method:

class Circle extends Shape implements Drawable {
    private double radius;

    public Circle(String color, double radius) {
        this.radius = radius;

    public double getArea() {
        return Math.PI * Math.pow(radius, 2);

    public void draw() {
        System.out.println("Drawing circle with radius " + radius + " and color " + getColor());


In this example, Circle is a subclass of Shape that implements its abstract method getArea(). It also implements the Drawable interface, and provides an implementation for its draw() method.

Abstraction is a powerful tool in OOP that helps to simplify complex systems by breaking them down into smaller, more manageable parts. It enables us to define the essential features of an object and hide the details of its implementation, making it easier to use and maintain.


There are several advantages of Java Abstraction, some of which are:


  1. Reduces Complexity: Abstraction allows us to focus on the essential features of an object, while hiding the implementation details. This reduces the complexity of the system, making it easier to understand and maintain.

  2. Encapsulation: Abstraction provides a way to encapsulate the implementation details of an object. This protects the object from external interference and makes it more secure.

  3. Flexibility: Abstraction allows us to create models of real-world objects that are flexible and can be easily extended or modified. This makes it easier to adapt the system to changing requirements.

  4. Code Reusability: Abstraction promotes code reusability by providing a way to define common behaviors and characteristics that can be inherited by multiple objects. This reduces code duplication and saves development time.

  5. Polymorphism: Abstraction enables polymorphism, which allows objects of different classes to be treated as if they were of the same class. This makes it easier to write generic code that can be used with different objects.


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