A06 - Shape class and derivation

Now we want to extend our Polygon example a bit more. This time we will use inheritance.¹

Step 1

Create an class Shape. This class needs the following member:

• a field for the position (Point2D) of the Shape
• a property with get and protected set for the area
• a constructor that take the position of that Shape as a parameter
• a protected method for the calculation of the area
  • it should return -1

Step 2

Let your Polygon class derive from Shape. Change the internal structure of Polygon so that there are no errors through the derivation.

Hint: Don’t forget the base constructor.

Step 3

Create a new class Circle that also derive from Shape. This class needs also the following member:

• a private field and public for the radius
  • if the radius changed (per set) it should recalculate the area
• a constructor that take the radius of that Circle as a parameter
• override the implementation of the given calculation method for the area

Step 4

Change the polygon creation method in the Program.

Create a new static² method in the Program class to create a Circle with user input. The radius should never be less or equal 0.

Hint: For the time being will use the (0, 0) point for the position of the shapes.