Shapes exercise

Shapes.java

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        var shapes = Arrays.asList(
                new Circle(3),
                new Rectangle(5, 10),
                new Square(5)
        );

        for (var shape : shapes)
            System.out.println(shape.getArea());
    }
}

interface Shape {
    double getArea();
}

class Circle implements Shape {
    private final double radius;

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

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

class Square implements Shape {
    private final double width;

    public Square(double width) {
        this.width = width;
    }

    @Override
    public double getArea() {
        return this.width * this.width;
    }
}

class Rectangle implements Shape {
    private final double width;
    private final double height;

    public Rectangle(double width, double height) {
        this.width = width;
        this.height = height;
    }

    @Override
    public double getArea() {
        return this.width * this.height;
    }
}