Question 1

To avoid duplicating code, use ________, rather than ________.

Accepted Answer

A)  inheritance, the "copy-and-past" approach. 
B)  the "copy-and-paste" approach, inheritance. 
C)  a class that explicitly extends Object, a class that does not extend Object. 
D)  a class that does not extend Object, a class that explicitly extends Object. 
A)  inheritance, the "copy-and-past" approach. 
B)  the "copy-and-paste" approach, inheritance. 
C)  a class that explicitly extends Object, a class that does not extend Object. 
D)  a class that does not extend Object, a class that explicitly extends Object. A

Question 2

Which superclass members are inherited by all subclasses of that superclass?

Accepted Answer

A)  private instance variables and methods. 
B)  protected instance variables and methods. 
C)  private constructors. 
D)  protected constructors. 
A)  private instance variables and methods. 
B)  protected instance variables and methods. 
C)  private constructors. 
D)  protected constructors. B

Question 3

When a subclass constructor calls its superclass constructor, what happens if the superclass's constructor does not assign a value to an instance variable?

Accepted Answer

A)  A syntax error occurs. 
B)  A compile-time error occurs. 
C)  A run-time error occurs. 
D)  The program compiles and runs because the instance variables are initialized to their default values. 
A)  A syntax error occurs. 
B)  A compile-time error occurs. 
C)  A run-time error occurs. 
D)  The program compiles and runs because the instance variables are initialized to their default values. D

Question 4

Which of the following is the superclass constructor call syntax?

Accepted Answer

A)  keyword super, followed by a dot (.) . 
B)  keyword super, followed by a set of parentheses containing the superclass constructor arguments. 
C)  keyword super, followed by a dot and the superclass constructor name. 
D)  None of the above. 
A)  keyword super, followed by a dot (.) . 
B)  keyword super, followed by a set of parentheses containing the superclass constructor arguments. 
C)  keyword super, followed by a dot and the superclass constructor name. 
D)  None of the above.

Question 5

The default implementation of method clone of Object performs a ________.

Accepted Answer

A)  empty copy. 
B)  deep copy. 
C)  full copy. 
D)  shallow copy. 
A)  empty copy. 
B)  deep copy. 
C)  full copy. 
D)  shallow copy.

Question 6

Which of the following keywords allows a subclass to access a superclass method even when the subclass has overridden the superclass method?

Accepted Answer

A)  base. 
B)  this. 
C)  public. 
D)  super. 
A)  base. 
B)  this. 
C)  public. 
D)  super.

Question 7

Every class in Java, except ________, extends an existing class.

Accepted Answer

A)  Integer. 
B)  Object. 
C)  String. 
D)  Class. 
A)  Integer. 
B)  Object. 
C)  String. 
D)  Class.

Question 8

The default equals implementation of class Object determines:

Accepted Answer

A)  whether two references refer to the same object in memory. 
B)  whether two references have the same type. 
C)  whether two objects have the same instance variables. 
D)  whether two objects have the same instance variable values. 
A)  whether two references refer to the same object in memory. 
B)  whether two references have the same type. 
C)  whether two objects have the same instance variables. 
D)  whether two objects have the same instance variable values.

Question 9

Which of the following statements is false?

Accepted Answer

A)  A subclass is often larger than its superclass. 
B)  A superclass object is a subclass object. 
C)  The class following the extends keyword in a class declaration is the direct superclass of the class being declared. 
D)  Java uses interfaces to provide the benefits of multiple inheritance. 
A)  A subclass is often larger than its superclass. 
B)  A superclass object is a subclass object. 
C)  The class following the extends keyword in a class declaration is the direct superclass of the class being declared. 
D)  Java uses interfaces to provide the benefits of multiple inheritance.

Question 10

When overriding a superclass method and calling the superclass version from the subclass method, failure to prefix the superclass method name with the keyword super and a dot (.) in the superclass method call causes ________.

Accepted Answer

A)  a compile-time error. 
B)  a syntax error. 
C)  infinite recursion. 
D)  a runtime error. 
A)  a compile-time error. 
B)  a syntax error. 
C)  infinite recursion. 
D)  a runtime error.

Question 11

Which method changes the text the label displays?

Accepted Answer

A)  changeText. 
B)  setText. 
C)  changeLabel. 
D)  setLabel. 
A)  changeText. 
B)  setText. 
C)  changeLabel. 
D)  setLabel.

Question 12

Using the protected keyword also gives a member:

Accepted Answer

A)  public access. 
B)  package access. 
C)  private access. 
D)  block scope. 
A)  public access. 
B)  package access. 
C)  private access. 
D)  block scope.

Question 13

private fields of a superclass can be accessed in a subclass

Accepted Answer

A)  by calling private methods declared in the superclass. 
B)  by calling public or protected methods declared in the superclass. 
C)  directly. 
D)  All of the above. 
A)  by calling private methods declared in the superclass. 
B)  by calling public or protected methods declared in the superclass. 
C)  directly. 
D)  All of the above.

Question 14

An advantage of inheritance is that:

Accepted Answer

A)  All methods can be inherited. 
B)  All instance variables can be uniformly accessed by subclasses and superclasses. 
C)  Objects of a subclass can be treated like objects of their superclass. 
D)  None of the above. 
A)  All methods can be inherited. 
B)  All instance variables can be uniformly accessed by subclasses and superclasses. 
C)  Objects of a subclass can be treated like objects of their superclass. 
D)  None of the above.

Question 15

Which statement is true when a superclass has protected instance variables?

Accepted Answer

A)  A subclass object can assign an invalid value to the superclass's instance variables, thus leaving an object in an inconsistent state. 
B)  Subclass methods are more likely to be written so that they depend on the superclass's data implementation. 
C)  We may need to modify all the subclasses of the superclass if the superclass implementation changes. 
D)  All of the above. 
A)  A subclass object can assign an invalid value to the superclass's instance variables, thus leaving an object in an inconsistent state. 
B)  Subclass methods are more likely to be written so that they depend on the superclass's data implementation. 
C)  We may need to modify all the subclasses of the superclass if the superclass implementation changes. 
D)  All of the above.

Question 16

Superclass methods with this level of access cannot be called from subclasses.

Accepted Answer

A)  private. 
B)  public. 
C)  protected. 
D)  package. 
A)  private. 
B)  public. 
C)  protected. 
D)  package.

Question 17

Which of the following is not a superclass/subclass relationship?

Accepted Answer

A)  Employee/Hourly Employee. 
B)  Vehicle/Car. 
C)  Sailboat/Tugboat. 
D)  None of the above. 
A)  Employee/Hourly Employee. 
B)  Vehicle/Car. 
C)  Sailboat/Tugboat. 
D)  None of the above.

Question 18

Class ________ represents an image that can be displayed on a JLabel.

Accepted Answer

A)  Image. 
B)  Icon. 
C)  ImageIcon. 
D)  IconImage. 
A)  Image. 
B)  Icon. 
C)  ImageIcon. 
D)  IconImage.

Question 19

Inheritance is also known as the

Accepted Answer

A)  knows-a relationship. 
B)  has-a relationship. 
C)  uses-a relationship. 
D)  is-a relationship. 
A)  knows-a relationship. 
B)  has-a relationship. 
C)  uses-a relationship. 
D)  is-a relationship.

Question 20

Consider the classes below, declared in the same file:
Class A
{
Int a;
Public A()
{
A = 7;
}
}
Class B extends A
{
Int b;
Public B()
{
B = 8;
}
}
Which of the statements below is false?

Accepted Answer

A)  Both variables a and b are instance variables. 
B)  After the constructor for class B executes, the variable a will have the value 7. 
C)  After the constructor for class B executes, the variable b will have the value 8. 
D)  A reference of type A can be treated as a reference of type B. 
A)  Both variables a and b are instance variables. 
B)  After the constructor for class B executes, the variable a will have the value 7. 
C)  After the constructor for class B executes, the variable b will have the value 8. 
D)  A reference of type A can be treated as a reference of type B.

Exam 9: Object Oriented Programming: Inheritance

To avoid duplicating code, use ________, rather than ________.

Which superclass members are inherited by all subclasses of that superclass?

When a subclass constructor calls its superclass constructor, what happens if the superclass's constructor does not assign a value to an instance variable?

Which of the following is the superclass constructor call syntax?

The default implementation of method clone of Object performs a ________.

Which of the following keywords allows a subclass to access a superclass method even when the subclass has overridden the superclass method?

Every class in Java, except ________, extends an existing class.

The default equals implementation of class Object determines:

Which of the following statements is false?

When overriding a superclass method and calling the superclass version from the subclass method, failure to prefix the superclass method name with the keyword super and a dot (.) in the superclass method call causes ________.

Which method changes the text the label displays?

Using the protected keyword also gives a member:

private fields of a superclass can be accessed in a subclass

An advantage of inheritance is that:

Which statement is true when a superclass has protected instance variables?

Superclass methods with this level of access cannot be called from subclasses.

Which of the following is not a superclass/subclass relationship?

Class ________ represents an image that can be displayed on a JLabel.

Inheritance is also known as the

Consider the classes below, declared in the same file: Class A { Int a; Public A() { A = 7; } } Class B extends A { Int b; Public B() { B = 8; } } Which of the statements below is false?

Introduction to Computers and Java

Introduction to Java Applications

Control Statements

Control Statements

Methods

Arrays and Arraylists

Introduction to Classes and Objects

Classes and Objects: a Deeper Look

Object-Oriented Programming: Polymorphism

Exception Handling

Gui Components

Graphics and Java 2D

Fundamentals of Characters and Strings

Files, Streams and Object Serialization

Generic Collections

Lambdas

Recursion

Searching, Sorting and Big O

Generic Classes and Methods

Custom Generic Data Structures

GUI

Concurrency

Accessing Databases With JDBC

JavaFX

Filters

To avoid duplicating code, use , rather than .