The ShapeTest class contains incomplete codes in the main method. You need to complete those missing lines of codes to test the polymorphic behaviour by calling the calculateArea method appropriately.

// an interface interface Shape { public double calculateArea();

}

//Rectangle class

class Rectangle implements Shape {

// fields/variables

double length;

double width;

//constructor

public Rectangle(double length, double width)

{ setLength(length); setWidth(width); }

//getters and setters

public double getLength()

{ return length; }

public void setLength(double length)

{ if(length > 0) this.length = length; }

public double getWidth()

{ return width; }

public void setWidth(double width)

{ if(width > 0) this.width = width; }

// returning the area of rectangle public double calculateArea()

{ return length * width; }

}// end of Rectangle class

//Circle class

class Circle implements Shape

{ // fields/variables double radius; //constructor public Circle(double radius) { setRadius(radius); }

//getters and setters

public double getRadius()

{ return radius; }

public void setRadius(double radius)

{ if(radius > 0) this.radius = radius; else this.radius = 0.0; }

// returning area of circle public double calculateArea()

{ return Math.PI * radius * radius; } }

// to test the objects of Rectangle and Circle

public class ShapeTest { public static void main(String [] args)

{ Shape [ ] diagrams = new Shape [3];

// Create three shape objects and test the polymorphic behavior by calling calculateArea() method //Missing lines of codes have to be completed} }