Abstraction and Interfaces in Java

 Abstraction and interfaces are two crucial Java concepts that support the creation of modular and adaptable program designs. Let's investigate each of these ideas:

Abstraction: 

A key idea of object-oriented programming is abstraction, which focuses on concealing intricate implementation details and exposing only the necessary characteristics of an object. You can use it to produce a condensed illustration of an object's activity. Through abstract classes and methods, this is accomplished.

Abstract classes: A class that cannot be instantiated on its own is said to be abstract. It acts as a template from which other classes can inherit. Both abstract methods (methods without a body) and concrete methods (methods with implementation) can be found in abstract classes. All the abstract methods declared in an abstract class must have implementations in subclasses that derive from it.

Example:

abstract class Shape {

    abstract double area(); // Abstract method without implementation

    void display() {

        System.out.println("Displaying shape.");

    }

}

class Circle extends Shape {

    double radius;

    Circle(double radius) {

        this.radius = radius;

    }  

    @Override

    double area() {

        return Math.PI * radius * radius;

    }

}

Interfaces:

An interface is a set of methods that a class is required to implement. Because a class can implement multiple interfaces, it enables multiple inheritance in Java. Polymorphism and loose coupling are made possible by the way interfaces ensure that classes follow a specific contract.

Interface Declaration:

interface Drawable {

    void draw(); // Method signatures without implementation

    void resize(int factor);

}

Class Implementing an Interface:

class Circle implements Drawable {

    private double radius;

    

    Circle(double radius) {

        this.radius = radius;

    }

    

    @Override

    public void draw() {

        System.out.println("Drawing circle.");

    }

    

    @Override

    public void resize(int factor) {

        radius *= factor;

    }

}

Interface Inheritance:

You can create a hierarchy of interfaces since interfaces can extend one another.

interface Shape extends Drawable {

    double area();

}

In conclusion, abstraction enables you to set contracts that classes must abide by, increasing flexibility and modularity in your code, whereas interfaces give you a mechanism to define such contracts. When creating extendable and maintainable Java applications, both ideas are essential.