tutorial5-s2-2019.java

public class Program {
    public static void main(String[] args) {
        Shape[] shapes = new Shape[3];
        sgihapes[0] = new Circle(0, 0, 1);
        shapes[1] = new Rectangle(0, 0, 2, 1);
        shapes[2] = new Circle(1, 1, 1);

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

public abstract class Shape {
    private double x;
    private double y;

    public Shape(double x, double y) {
        this.x = x;
        this.y = y;
    }

    public double getX() {
        return x;
    }
    public double getY() {
        return y;
    }

    public abstract double getArea();
}

class Rectangle extends Shape {
    private double width;
    private double height;

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

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

class Circle extends Shape {
    private double radius;

    public Circle(double x, double y, double radius) {
        super(x, y);
        this.radius = radius;
    }

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

    @Override
    public String toString() {
        return "Centre: (" + getX() + ", " + getY() + "), radius: " + radius;
    }

    @Override
    public boolean equals(Object rhs) {
        if (rhs instanceof Circle) {
            // Downcasting!
            Circle other = (Circle) rhs;
            return other.getX() == getX() && other.getY() == getY()
                && radius == other.radius;
        } else {
            return false;
        }
    }
}