Question 1

Overriding a method differs from overloading a method because:

Accepted Answer

A) Overloaded methods have the same signature. 
B) Overridden methods have the same signature. 
C) Both of the above. 
D) Neither of the above. 
A) Overloaded methods have the same signature. 
B) Overridden methods have the same signature. 
C) Both of the above. 
D) Neither of the above. B

Question 2

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. D

Question 3

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. B

Question 4

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 5

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 6

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 7

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 8

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 9

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 10

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

Accepted Answer

A) Ford/Taurus. 
B) University/Boston University. 
C) Sailboat/Tugboat. 
D) Country/USA. 
A) Ford/Taurus. 
B) University/Boston University. 
C) Sailboat/Tugboat. 
D) Country/USA.

Question 11

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.

Question 12

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

Accepted Answer

A) inheritance,the "copy-and-past" approach. 
B) the "copy-and-past" 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-past" 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.

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

Using the protected keyword 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 15

Which of the following statements is (are)true? a)We can use inheritance to customize existing software.
b)A superclass specifies commonality.
c)A superclass can be modified without modifying subclasses
d)A subclass can be modified without modifying its superclass.

Accepted Answer

A) All of the above. 
B) None of the above. 
C) A,B and C. 
D) A,B and D. 
A) All of the above. 
B) None of the above. 
C) A,B and C. 
D) A,B and D.

Question 16

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 17

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 18

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.

Question 19

Failure to prefix the superclass method name with the keyword super and a dot (. )separator when referencing the superclass's method 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 20

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.

Exam 9: Object Oriented Programming: Inheritance

Overriding a method differs from overloading a method because:

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?

Which of the following statements is false?

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.

Which of the following is the superclass constructor call syntax?

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

Which method changes the text the label displays?

Inheritance is also known as the

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

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

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

Private fields of a superclass can be accessed in a subclass

Using the protected keyword gives a member:

Which of the following statements is (are)true? a)We can use inheritance to customize existing software. b)A superclass specifies commonality. c)A superclass can be modified without modifying subclasses d)A subclass can be modified without modifying its superclass.

An advantage of inheritance is that:

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

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

Failure to prefix the superclass method name with the keyword super and a dot (. )separator when referencing the superclass's method causes ________.

The default equals implementation of class Object determines:

Introduction to Computers and Java

Introduction to Java Applications

Introduction to Classes and Objects

Control Statements: Part 1

Control Statements: Part 2

Methods: a Deeper Look

Arrays and Arraylists

Classes and Objects: a Deeper Look

Object-Oriented Programming: Polymorphism

Exception Handling

Atm Case Study,part 1: Object-Oriented Design With the Uml

Atm Case Study,part 2: Implementing an Object-Oriented Design

Gui Components: Part 1

Graphics and Java 2d

Strings

Files,streams and Object Serialization

Recursion

Searching, Sorting and Big O

Generic Collections

Generic Classes and Methods

Custom Generic Data Structures

Applets and Java Web Start

Multimedia: Applets and Applications

Gui, Part 2

Multithreading

Networking

Accessing Databases With Jdbc

Java Server Faces Web Applications

Ajax-Enabled Jsf Web Applications

Web Services

Filters

To avoid duplicating code,use ,rather than .