Description
As was taught earlier in the semester, Java allows the declaraon of both classes and interfaces.
Being an object-oriented programming language, it also allows classes/interfaces to
extend/implement others through a concept called inheritance.
An interface can be thought of as a contract. Any concrete class that implements an interface
must provide declaraons for methods contained in it. An abstract class is similar to an
interface, in that it requires its concrete subclasses to provide declaraons for its abstract
methods. Abstract classes, though, can also contains fields and constructors.
The power of both interfaces and abstract classes is that types can be related, making an
asseron that subtypes have certain methods in common. For example, AbstractList is an
abstract class held in the java.util package. It contains a get() method that is marked as
abstract. This means that its subclasses, such as ArrayList , must provide a declaraon for
that method.
One can declare a field of type AbstractList , and will know for a fact that any reference it
holds has a get() implementaon. This allows an exisng implementaon to be swapped out
for a potenally beer one, and not break exisng code.
You will be experiment with abstract classes through polyhedrabelow.
Description
Your task for this homework is to create three classes — Polyhedron , Tetrahedron , and
Icosahedron . Polyhedron is an abstract class, of which both Tetrahedron and
Icosahedron extend. Field, constructor, and method declaraons for each are listed below.
Polyhedron
Fields
Name Type Access Modifier
sideLength double private
Constructor
Parameters Access Modifier
double sideLength1 public
Methods
Name Return
Type
Parameters Access
Modifier
Abstract
getSideLength double None public ✗
setSideLength2 void double sideLength public ✗
equals boolean Object anObject public ✗
toString String None public ✗
getSurfaceArea double None public ✓
getVolume double None public ✓
1 An IllegalArgumentException should be thrown if the sideLength argument is negave
2 See 1
Tetrahedron
Supertype
Name
Polyhedron
Constructor
Parameters Access Modifier
double sideLength3 public
Methods
Name Return
Type
Parameters Access Modifier
getSurfaceArea4 double None public
getVolume5 double None public
equals boolean Object anObject public
toString String None public
3 An IllegalArgumentException should be thrown if the sideLength argument is negave
4 Surface area formula: sqrt(3.0) * (sideLength)^2
5 Volume formula: (sideLength)^3 / (6.0 * sqrt(2.0))
Icosahedron
Supertype
Name
Polyhedron
Constructor
Parameters Access Modifier
double sideLength6 public
Methods
Name Return
Type
Parameters Access Modifier
getSurfaceArea7 double None public
getVolume8 double None public
equals boolean Object anObject public
toString String None public
6 An IllegalArgumentException should be thrown if the sideLength argument is negave
7 Surface area formula: 5.0 * sqrt(3.0) * (sideLength)^2
8 Volume formula: ((15.0 + (5.0 * sqrt(5.0))) / 12.0) * (sideLength)^3
equals() and toString() implementations
The equals() method in each class should first determine if the specified object is an
instance of the class. If it is, the side length of each should be compared for exact equality.
The toString() method in each class should return a String of the form
ClassName[sideLength] , where ClassName is the class’s name, and sideLength is the value of the
sideLength field displayed with six decimal places (Hint: the format specified %f displays six
decimal places by default).
JavaDoc
If you would like to view the JavaDoc for this homework, you may do so by going here . All
necessary informaon is contained in this handout, though.
Submission
You are required to complete three classes — Polyhedron , Tetrahedron , and
Icosahedron — that follow the specificaons outlined above.
Submit all three .java files to Vocareum through Blackboard . Keep in mind that your latest
submission will be the one transferred to the gradebook.
Grading Rubric
– Polyhedron class (40 points)
– 2.5 points
– Making Polyhedron abstract
– Declaring the sideLength field
– 5 points for each constructor/method declaraon (7 total)
– 30 points
– Tetrahedron class
– 3 points for extending Polyhedron
– 5.4 points for each constructor/method declaraon (5 total)
– Icosahedron class
– 3 points for extending Polyhedron
– 5.4 points for each constructor/method declaraon (5 total)
