Question 1

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

Accepted Answer

A)  public.
B)  interface.
C)  abstract.
D)  final.E) A) and B)
F) A) and C)

Question 2

Consider classes A,B and C,where A is an abstract superclass,B is a concrete class that inherits from A and C is a concrete class that inherits from B.Class A declares abstract method originalMethod,implemented in class B.Which of the following statements is true of class C?

Accepted Answer

A)  Method originalMethod cannot be overridden in class C-once it has been implemented in concrete class B,it is implicitly final.
B)  Method originalMethod must be overridden in class C,or a compilation error will occur.
C)  If method originalMethod is not overridden in class C but is called by an object of class C,an error occurs.
D)  None of the above.E) A) and D)
F) All of the above

Question 3

The UML distinguishes an interface from other classes by placing the word "interface" in above the interface name.

Accepted Answer

A)  italics.
B)  carets.
C)  guillemets.
D)  bold.E) A) and B)
F) B) and C) C

Question 4

Assigning a subclass reference to a superclass variable is safe ________.

Accepted Answer

A)  because the subclass object has an object of its superclass.
B)  because the subclass object is an object of its superclass.
C)  only when the superclass is abstract.
D)  only when the superclass is concrete.E) B) and C)
F) A) and B)

Question 5

A(n)  class cannot be instantiated.

Accepted Answer

A)  final.
B)  concrete.
C)  abstract.
D)  polymorphic.E) B) and D)
F) B) and C)

Question 6

Which of the following statements is false?

Accepted Answer

A)  References to interface types do not have access to method toString.
B)  Method toString can be invoked implicitly on any object.
C)  With inheritance,classes and their inherited classes tend to be very similar.
D)  Dramatically different classes can often meaningfully implement the same interface.E) A) and B)
F) A) and C)

Question 7

Which of the following is not possible?

Accepted Answer

A)  A class that implements two interfaces.
B)  A class that inherits from two classes.
C)  A class that inherits from one class,and implements an interface.
D)  All of the above are possible.E) B) and C)
F) C) and D)

Question 8

Which of the following statements is false?

Accepted Answer

A)  In Java SE 8,an interface may declare default methods-that is,public methods with concrete implementations that specify how an operation should be performed.
B)  When a class implements an interface,the class receives the interface's default concrete implementations if it does not override them.
C)  When you enhance an existing interface with default methods-any class that implemented the original interface will break.
D)  With default methods,you can declare common method implementations in interfaces (rather than abstract classes) ,which gives you more flexibility in designing your classes.E) A) and B)
F) A) and D)

Question 9

Which statement best describes the relationship between superclass and subclass types?

Accepted Answer

A)  A subclass reference cannot be assigned to a superclass variable and a superclass reference cannot be assigned to a subclass variable.
B)  A subclass reference can be assigned to a superclass variable and a superclass reference can be assigned to a subclass variable.
C)  A superclass reference can be assigned to a subclass variable,but a subclass reference cannot be assigned to a superclass variable.
D)  A subclass reference can be assigned to a superclass variable,but a superclass reference cannot be assigned to a subclass variable.E) A) and C)
F) B) and C)

Question 10

Which of the following statements is false?

Accepted Answer

A)  As of Java SE 8,any interface containing only one method is known as a functional interface.
B)  There are many functional interfaces throughout the Java APIs.
C)  Functional interfaces are used extensively with Java SE 8's new lambda capabilities.
D)  Anonymous methods provide a shorthand notation for creating lambdas.E) A) and B)
F) A) and C) D

Question 11

Which of the following statements is false?

Accepted Answer

A)  Prior to Java SE 8,it was common to associate with an interface a class containing static helper methods for working with objects that implemented the interface.
B)  Class Collections contains many static helper methods for working with objects that implement interfaces Collection,List,Set and more.
C)  Collections method sort can sort objects of any class that implements interface List.
D)  With non-static interface methods,helper methods can now be declared directly in interfaces rather than in separate classes.E) A) and C)
F) C) and D)

Question 12

If the superclass contains only abstract method declarations,the superclass is used for ________.

Accepted Answer

A)  implementation inheritance.
B)  interface inheritance.
C)  Both.
D)  Neither.E) A) and D)
F) C) and D)

Question 13

Which of the following statements about abstract superclasses is true?

Accepted Answer

A)  abstract superclasses may contain data.
B)  abstract superclasses may not contain implementations of methods.
C)  abstract superclasses must declare all methods as abstract.
D)  abstract superclasses must declare all data members not given values as abstract.E) A) and D)
F) C) and D) A

Question 14

When a superclass variable refers to a subclass object and a method is called on that object,the proper implementation is determined at execution time.What is the process of determining the correct method to call?

Accepted Answer

A)  early binding.
B)  non-binding.
C)  on-time binding.
D)  late binding.E) A) and B)
F) All of the above

Question 15

All of the following methods are implicitly final except:

Accepted Answer

A)  a method in an abstract class.
B)  a private method.
C)  a method declared in a final class.
D)  static method.E) A) and B)
F) A) and D)

Question 16

For which of the following would polymorphism not provide a clean solution?

Accepted Answer

A)  A billing program where there is a variety of client types that are billed with different fee structures.
B)  A maintenance log program where data for a variety of types of machines is collected and maintenance schedules are produced for each machine based on the data collected.
C)  A program to compute a 5% savings account interest for a variety of clients.
D)  An IRS program that maintains information on a variety of taxpayers and determines who to audit based on criteria for classes of taxpayers.E) B) and D)
F) A) and B)

Question 17

Which of the following is false?

Accepted Answer

A)  You should not call overridable methods from constructors-when creating a subclass object,this could lead to an overridden method being called before the subclass object is fully initialized.
B)  It's OK to any of a class's methods from its constructors.
C)  When you construct a subclass object,its constructor first calls one of the direct superclass's constructors.If the superclass constructor calls an overridable method,the subclass's version of that method will be called by the superclass constructor.
D)  It's acceptable to call a static method from a constructor.E) B) and C)
F) C) and D)

Question 18

In Java SE 7 and earlier,an interface may contain:

Accepted Answer

A)  private static data and public abstract methods.
B)  only public abstract methods.
C)  public static final data and public abstract methods.
D)  private static data and public final methods.E) A) and C)
F) C) and D)

Question 19

Polymorphism allows for specifics to be dealt with during:

Accepted Answer

A)  execution.
B)  compilation.
C)  programming.
D)  debugging.E) None of the above
F) C) and D)

Question 20

Interfaces can have methods.

Accepted Answer

A)  0
B)  1
C)  2
D)  any number ofE) A) and D)
F) C) and D)

Exam 10: Object-Oriented Programming: Polymorphism

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

Correct AnswerverifiedShow Answer

Consider classes A,B and C,where A is an abstract superclass,B is a concrete class that inherits from A and C is a concrete class that inherits from B.Class A declares abstract method originalMethod,implemented in class B.Which of the following statements is true of class C?

Correct AnswerverifiedShow Answer

The UML distinguishes an interface from other classes by placing the word "interface" in above the interface name.

Correct AnswerverifiedC

Assigning a subclass reference to a superclass variable is safe ________.

Correct AnswerverifiedShow Answer

A(n) class cannot be instantiated.

Correct AnswerverifiedShow Answer

Which of the following statements is false?

Correct AnswerverifiedShow Answer

Which of the following is not possible?

Correct AnswerverifiedShow Answer

Which of the following statements is false?

Correct AnswerverifiedShow Answer

Which statement best describes the relationship between superclass and subclass types?

Correct AnswerverifiedShow Answer

Which of the following statements is false?

Correct AnswerverifiedD

Which of the following statements is false?

Correct AnswerverifiedShow Answer

If the superclass contains only abstract method declarations,the superclass is used for ________.

Correct AnswerverifiedShow Answer

Which of the following statements about abstract superclasses is true?

Correct AnswerverifiedA

When a superclass variable refers to a subclass object and a method is called on that object,the proper implementation is determined at execution time.What is the process of determining the correct method to call?

Correct AnswerverifiedShow Answer

All of the following methods are implicitly final except:

Correct AnswerverifiedShow Answer

For which of the following would polymorphism not provide a clean solution?

Correct AnswerverifiedShow Answer

Which of the following is false?

Correct AnswerverifiedShow Answer

In Java SE 7 and earlier,an interface may contain:

Correct AnswerverifiedShow Answer

Polymorphism allows for specifics to be dealt with during:

Correct AnswerverifiedShow Answer

Interfaces can have methods.

Correct AnswerverifiedShow Answer

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C

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D

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A

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