Deck 12: Object-Oriented Programming: Polymorphism

Question 1

Unfortunately,polymorphic programs make it difficult to add new capabilities to a system.

Answer 1

False
Polymorphic programs make it easy to add new capabilities to a system.

Question 2

Polymorphism allows the addition of classes providing they were at least considered during program development.

Answer 2

False
Polymorphism can be used to include classes that were not even envisioned during program development.

Question 3

Polymorphism enables you to:

A) program in the general.
B) program in the specific.
C) absorb attributes and behavior from previous classes.
D) hide information from the user.

Answer 3

A

Question 4

Concrete classes provide implementations for every method and property they define.

Question 5

Abstract classes may not be:

A) inherited
B) accessed by derived-classes
C) instantiated
D) None of the above.

Question 6

Polymorphism allows classes to be added with little or no modifications to the generic portion of a program.

Question 7

Polymorphism helps promote software extensibility.

Question 8

Which statement best describes the relationship between base class and derived class types

A)A derived class reference cannot be assigned to a base class variable and a base class
Reference cannot be assigned to a derived class variable.
B)A derived class reference can be assigned to a base class variable and a base class
Reference can be assigned to a derived class variable.
C)A base class reference can be assigned to a derived class variable,but a derived class
Reference cannot be assigned to a base class variable.
D)A derived class reference can be assigned to a base class variable,but a base class
Reference cannot be assigned to a derived class variable.

Question 9

Which of the following is false about interfaces

A) An interface describes a set of methods that can be called on an object, providing a default implementation for the methods.
B) An interface describes a set of methods that can be called on an object, without providing concrete implementation for the methods.
C) Interfaces are useful when attempting to assign common functionality to possibly unrelated classes.
D) Once a class implements an interface, all objects of that class have an is-a relationship with the interface type.

Question 10

When a request is made to use a derived-class-object method through a base-class reference,C# polymorphically chooses the correct overridden method in the appro
priate derived class that's associated with the object.

Question 11

Polymorphism allows for specifics to be dealt with during:

A)execution
B)compilation
C)programming
D)debugging

Question 12

The abstract methods and properties of a class do not provide an implementation.

Question 13

If a derived class reference is assigned to a base class variable,the variable must be cast back to the derived class before any derived class methods can be called with it.

Question 14

Polymorphism allows you to command a wide variety of objects even if you do not know the objects' types.

Question 15

Polymorphism enables objects of different classes that are related by a class hierarchy to be processed generically.

Question 16

If an app needs to perform a derived-class-specific operation on a derived class object reference by a base class variable,the app must first cast the base class reference to a derived class reference through a technique known as _________.

A) downcasting
D) increasecasting

Question 17

Polymorphism specifically enables the creation of programs that handle:

A) classes that are containers for other classes
B) large amounts of data with efficiency
C) a wide variety of classes in a general manner
D) None of the above

Question 18

When used correctly,polymorphism will never require changes to be made to any part of the program.

Question 19

The major drawback to polymorphically designed programs is that they do not take into account the future addition or deletion of classes.

Question 20

Polymorphism involves:

A) the same message sent to a variety of objects, which each interpret their own way
B) a specific message sent to each specific object
C) different messages sent to one object
D) None of the above.

Question 21

An abstract class cannot have instance data and non-abstract methods.

Question 22

Assigning a derived class reference to a base class variable is safe:

A)because the derived class has an object of its base class.
B)because the derived class is an object of its base class.
C)only when the base class is abstract.
D)only when the base class is concrete.

Question 23

You may define implementations for abstract methods to act as default implementations.

Question 24

Consider the abstract class below:
Public abstract class Foo
{
Private int a;
Public int b;
Public Foo(int aVal,int bVal)
{
A = aVal;
B = bVal;
}
Public abstract int calculate();
}
Any concrete subclass that extends class Foo:

A) Must implement a method called calculate.
B) Will not be able to access the instance variable a.
C) Will not be able to instantiate an object of class Foo.
D) All of the above.

Question 25

Operator is returns true if two matching types are being compared.

Question 26

The keyword sealed is applied to methods and classes to:

A) prevent overriding and inheritance
B) guarantee an implementation exists
C) specify a class is concrete
D) None of the above.

Question 27

Classes and methods are declared sealed for all of the following reasons,except:

A) sealed methods allow inlining the code.
B) sealed methods and classes prevent further inheritance.
C) sealed methods are static.
D) sealed methods can improve performance.

Question 28

An abstract base class can be used to declare references.

Question 29

An abstract class may be derived from another abstract class.

Question 30

Which of the following statements about abstract base classes is true

A) abstract base classes may contain data.
B) abstract base classes may not contain implementations of methods.
C) abstract base classes must declare all methods as abstract.
D) abstract base classes must declare all data members not given values as abstract.

Question 31

A convention of the UML is to denote the name of an abstract class in:

A) bold
B) italics
C) a diamond
D) there is no convention of the UML to denote abstract classes-they are listed just as any other class

Question 32

If the base class contains only abstract method declarations,the base class is used for:

A) implementation inheritance.
B) interface inheritance.
C) Both.
D) Neither.

Question 33

All methods in an abstract class are inherently abstract.

Question 34

________ code is the process by which the compiler replaces method calls with the code of a method to improve performance.

A) Debugging
B) Inlining
C) Compiling
D) None of the above.

Question 35

If a method needs to be called polymorphically,what type of reference should be used to point to the object that the method is being called with

A) a reference of the base class that defines the behavior of the object
B) a reference of the same type as the object
C) an object reference to the actual object
D) None of the above.

Question 36

Attempting to instantiate an object of an abstract class is a logic error.

Question 37

Which declaration declares abstract method method1 in abstract class Class1 (method1 returns an int and takes no arguments)

A) public int method1();
B) public int abstract method1();
C) public abstract int method1();
D) public int nonfinal method1();

Question 38

Objects of abstract base classes can be instantiated.

Question 39

Every object in C# knows its own class and can access this information through method

A) GetType()
B) GetInformation()
C) ObjectClass()
D) ObjectInformation()

Question 40

The abstract keyword has the same effect as the virtual keyword.

Question 41

Sealing methods allows the compiler to optimize the program by "inlining code."

Question 42

Declaring a method sealed means:

A) it will prepare the object for garbage collection
B) it cannot be accessed from outside its class
C) it cannot be overloaded
D) it cannot be overridden

Question 43

Which of the following characteristics could be used to create an interface for a file,a cat and a house

A) door
B) tail
C) age
D) None of the above.

Question 44

A(n)________ is best used for providing services that bring together objects of otherwise unrelated classes.

A) abstract class
B) concrete class
C) interface
D) None of the above.

Question 45

A concrete class that implements an interface must define all methods and properties of that interface.

Question 46

Abstract classes can provide data and services for objects.

Question 47

Interfaces can have methods.

A) 0
B) 1
C) 2
D) any number of

Question 48

By convention,the name for a Car interface is:

A) InterfaceCar
B) ICar
C) CarI
D) None of the above.

Question 49

Constants declared in an interface are implicitly _______.

A)private.
B)static.
C)abstract.
D)All of the above.

Question 50

Which of the following does not complete the sentence correctly
An interface.

A) forces classes that implement it to declare all the interface methods.
B) is used in place of an abstract class when there is no default implementation to inherit.
C) cannot be instantiated.
D) can be instantiated.

Question 51

All methods in a sealed class must be explicitly declared sealed.

Question 52

A class that implements an interface but does not declare all of the interface's methods must be declared:

A) public
B) interface
C) abstract
D) final

Question 53

All static and private methods are implicitly sealed.

Question 54

An interface is typically used in place of an abstract class when there is no default implementation to inherit.

Question 55

Declaring an interface protected allows for extra security precautions.

Question 56

The purpose of an interface is to:

A) provide similar objects with the same functionality, even though each will imple
B) provide different types of objects with the comparable functionality, even though each will imple
C) provide default implementations of methods and properties
D) None of the above.

Question 57

Which is used to specify that a class will be implementing an interface

A) using
B) :
C) implements
D) extends

Question 58

If a class leaves one method in an interface undeclared,the class is implicitly declared by C# as an abstract class.

Question 59

An interface can not provide properties with get and set accessors.

Question 60

All of the following methods are implicitly sealed except:

A) a method in an abstract class.
B) a private method.
C) a method declared in a sealed class.
D) static method.

Question 61

A class that implements an interface may not act as a base class for other classes.

Question 62

An interface reference may invoke only the methods that the interface declares.