Practice›Java Fundamentals›Module 8. Interfaces & Abstract Classes›8.3 Abstract classes

Task 6 of 7 · 0 solved · 7 to go0%

You can read the problem, but answers are checked only for signed-in students. Sign in to answer →

8.3 Abstract classes — total area

Total: 0 / 3 pts

Practice mode — check each part and get hints as you go.

Task

Fill in totalArea so that it returns the total area. Here the array type is the abstract class rather than an interface — the polymorphism works exactly the same way.

The program prints 9.14.

Your solution

abstract class Shape {
    private String name;

    public Shape(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public abstract double area();

    public String describe() {
        return name + " has area " + area();
    }
}

class Circle extends Shape {
    private double r;

    public Circle(double r) {
        super("Circle");
        this.r = r;
    }

    public double area() {
        return 3.14 * r * r;
    }
}

class Rect extends Shape {
    private double w;
    private double h;

    public Rect(double w, double h) {
        super("Rect");
        this.w = w;
        this.h = h;
    }

    public double area() {
        return w * h;
    }
}

public class Main {

    public static double totalArea(Shape[] shapes) {
        // add up the area of every shape

    }

    public static void main(String[] args) {
        Shape[] shapes = {new Circle(1), new Rect(2, 3)};
        System.out.println(totalArea(shapes));
    }
}

Next task →