Java Abstraction

Abstraction is another fundamental concept in Object-Oriented Programming (OOP) and is a feature of Java.

It is the process of hiding the implementation details of a class and exposing only the essential features to the users. In other words, abstraction is the concept of showing only what is necessary and hiding everything else.

There are two ways to achieve abstraction in Java: abstract classes and interfaces.

Abstract Classes

An abstract class is a class that cannot be instantiated on its own and is meant to be used as a base class for other classes. An abstract class can contain both abstract and non-abstract methods.

Abstract methods are methods that have no implementation and must be overridden by any concrete subclass. Here's an example of an abstract class in Java:

abstract class Shape {
    abstract void draw();
}
 
class Circle extends Shape {
    void draw() {
        System.out.println("Drawing a Circle");
    }
}
 
class Square extends Shape {
    void draw() {
        System.out.println("Drawing a Square");
    }
}

In the above example, the Shape class is an abstract class that has an abstract method draw(). The Circle and Square classes extend the Shape class and provide their own implementations of the draw() method, which is an example of abstraction in action.

Interfaces

An interface is a collection of abstract methods and constant variables.

Unlike abstract classes, interfaces cannot contain any implementation code. All the methods in an interface are abstract by default. Here's an example of an interface in Java:

interface Drawable {
    void draw();
}
 
class Circle implements Drawable {
    void draw() {
        System.out.println("Drawing a Circle");
    }
}
 
class Square implements Drawable {
    void draw() {
        System.out.println("Drawing a Square");
    }
}

In the above example, the Drawable interface has an abstract method draw().

The Circle and Square classes implement the Drawable interface and provide their own implementations of the draw() method, which is an example of abstraction in action.

In conclusion, abstraction is a powerful feature of Java that allows developers to hide the implementation details of a class and focus on the essential features.

It is an important aspect of software development as it helps to simplify complex systems, making them easier to understand and maintain.