Question

Consider the following declaration for a class that will be used to represent rectangles.

public class Rectangle
{
  private double height;
  private double width;

  public Rectangle()
  {
    height = 2.0;
    width = 1.0;
  }

  public Rectangle(double w, double h)
  {
    height = h;
    width = w;
  }

  public double getHeight()
  {  return height;  }

  public double getWidth()
  {  return width;  }

  public void setHeight(double h)
  {  height = h;  }

  public void setWidth(double w)
  {  width = w;  }

  //Other methods not shown
}

A Square class which extends the Rectangle class is to be written. Which of the following constructors will cause an error upon compilation when added to this class?

(A) public Square()
{
  super(1.0, 1.0);
}

(B) public Square(double w)
{
  height = w;
  width = w;
}

(C) public Square()
{
  setHeight(1.0);
  setWidth(1.0);
}

(D) public Square(double w)
{
  super(w, w);
}

(E) public Square(double w)
{
  super();
  setHeight(w);
  setWidth(w);
}

Answer 1

 public Square(double w)
{
  height = w;
  width = w;
}

this constructor will cause a compilation error because we have directly assigned height = w and width = w whereas height and width are not defined in the class.

Correct way to set height and width is

public Square(double w)
{
  super();
  setHeight(w);
  setWidth(w);
}

where we are calling methods of Rectangle class to set the height and width.

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