Extending Interfaces in Java

interface interface-name2 extends interface-name1
{
     // code
}

package ch10.l5;

interface Shape {
    void draw(); // Common method to all shapes
}

interface TwoDShape extends Shape {
    double calculateArea(); // Specific to 2D shapes
}

interface ThreeDShape extends Shape {
    double calculateVolume(); // Specific to 3D shapes
}

//Circle Class (Implements TwoDShape)
class Circle implements TwoDShape {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    @Override
    public void draw() {
        System.out.println("Drawing Circle");
    }

    @Override
    public double calculateArea() {
        return Math.PI * radius * radius;
    }
}

//Sphere Class (Implements ThreeDShape)
class Sphere implements ThreeDShape {
    private double radius;

    public Sphere(double radius) {
        this.radius = radius;
    }

    @Override
    public void draw() {
        System.out.println("Drawing Sphere");
    }

    @Override
    public double calculateVolume() {
        return (4/3) * Math.PI * Math.pow(radius, 3);
    }
}

public class ExtendingInterface {

	public static void main(String[] args) {
		TwoDShape circle = new Circle(5);
        ThreeDShape sphere = new Sphere(5);

        circle.draw();
        System.out.println("Circle Area: " + circle.calculateArea());

        sphere.draw();
        System.out.println("Sphere Volume: " + sphere.calculateVolume());
	}
}

Drawing Circle
Circle Area: 78.53981633974483
Drawing Sphere
Sphere Volume: 392.6990816987241