Week 9

Question 1

A feature that allows us to perform an action in different ways

Answer 1

Polymorphism

Question 2

Does polymorphism allow you to program in the general or the specific?

Answer 2

Polymorphism allows you to program in the general, rather than the specific

Question 3

T/F - Polymorphism enables you to write programs that process objects that share the same superclass as if they were all objects of the superclass

Answer 3

True

Question 4

A type defined by a subclass is called a _______, and a type defined by a superclass is called a _________

Answer 4

subtype, supertype

Question 5

The key concept of polymorphism: “Relying on each object ‘knowing how…’ to do what?

Answer 5

Knowing how to do the right thing in response to the same method call

Question 6

Why polymorphism powerful?

Answer 6

Makes the class flexible and extensible, simplifies programming by providing a single interface

Question 7

Method overriding allows subclasses to do what?

Answer 7

Allow for the reuse of code
Subclasses can use all the general definitions the superclass provides and add specializations by overriding methods

Question 8

What is the difference between polymorphism and inheritance?

Answer 8

Inheritance applies the behaviour of a superclass to a subclass.

Polymoprhism changes the behaviour of the superclass in the subclass.

Question 9

These are useful for assigning common functionality to possibly unrelated classes:

Answer 9

Interfaces

Question 10

2 unrelated classes implement the same interface, what happens with their methods and objects?

Answer 10

Classes that implement the same interface can have their objects respond to all of the interface method calls

Question 11

T/F - There are more types of polymorphism than inheritance

Answer 11

False, there are 2 types of polymorphism, 5 types of inheritance

Question 12

With polymorphism, we can design and implement systems that are _______ _________

Answer 12

easily extensible

Question 13

T/F - Interaces are useful for assigning common functionality to possibly unrelated classes

Answer 13

True

Question 14

T/F - Polymorphism enables you to deal in specifics

Answer 14

False, Polymorphism enables you to deal in generalities

Question 15

T/F - Objects will behave in an appropriate manner even if you do not know their type, as long as they belong to the same inheritance hierarchy

Answer 15

True

Question 16

How does polymorphism promote extensibility?

Answer 16

Software that invokes polymorphic behavior is independent of the object type that it is being used by

You can add new objects types without changing the base system

Only the client code that instantiates new objects must be changed

Question 17

What is a polymorphic reference?

Answer 17

A variable that can refer to different types of objects at different points of time

Question 18

T/F - All object references in Java are potentially polymorphic

Answer 18

True

Question 19

T/F - A method invoked through a polymorphic reference cannot change form from one invocation to the next

Answer 19

False

Question 20

Static polymorphism has method ________ing, dynamic polymorphism has method _________ing

Answer 20

Method overloading, method overriding

Question 21

How does method overloading different from method overriding?

Answer 21

Overloading is done at compile time, overriding at run-time

Question 22

Overidden vs. Overriding. How do they differ?

Answer 22

Overridden = parent class method
Overriding = child class method

Question 23

Can the argument list differ when method overriding?

Answer 23

No, must be same type and sequence

Question 24

I have a superclass method that is public, in the subclass I make the method private, will this work?

Answer 24

No. The access modifier cannot be more restrictive than the overridden method of the parent class

Question 25

Can private, static, or final methods be overriden? What is the caveat?

Answer 25

No, no, and no. Static methods can be re-declared, which would make the method act differently be completely separated from the superclass method

Question 26

Java defers method binding until run time, what is this called?

Answer 26

Dynamic binding, or late binding

Question 27

What would happen if binding was done at compile time?

Answer 27

It would call the same method every time

Question 28

Definition: Linking between the method call and method implementation is resolved at compile time

Answer 28

Static binding