Part 2: Interfaces

As covered in lectures, an interface is a set of methods. When a class implements an interface, the methods in the interface must be implemented in the class. The methods are not implemented in the interface, just listed.

1. Set up an interface called ThreeDShape that represents a 3D shape. Include an abstract method that allows the calculation of the volume of the 3D shape.

2. Amend the class hierarchy for shape to include two new subclasses representing the 3d shapes, cube and sphere. Get these classes to implement your new interface ThreeDShape. Hint 1: When a class implements an interface, it has to implement all methods in the interface. Hint 2: Implements keyword

3. Implement the area() method for the two new classes (cube and sphere) to return the surface area of the shape.

4. Modify the test class to test the new classes and methods you have added by including the new shapes (cube and sphere)in the array you have setup