Square as a subclass of Rectangle

Shapes

class Rectangle
{
    protected double width, height;

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

    public getWidth() { return this.width; }
    public getHeight() { return this.height; }
}

class Square  extends Rectangle
{
    constructor(double side)
    {
        parent.constructor(side, side);
    }
}