Deck 8: Inheritance

Question 1

A class declared as final _________________________________ .

A) cannot be changed.
B) cannot have subclasses.
C) cannot have superclasses.
D) has several abstract methods.
E) cannot be used in a program.

Answer 1

B
Explanation: The final modifier restricts inheritance. In particular, a class declared as final cannot have subclasses.

Question 2

Methods and variables declared as private in a parent class cannot be accessed in a child class.

Answer 2

True
Explanation: In order for a child class to have access to the private data and methods of a parent class, they should be declared using the protected modifier, which still enforces encapsulation, but allows for flexibility in an inheritance hierarchy.

Question 3

The special reference _________________ is used to refer to the parent class in a child class.

A) this
B) super
C) null
D) parent
E) none of the above

Answer 3

B
Explanation: The super reference refers to the parent class in a derived class.

Question 4

Once a method is overridden in a subclass, the original version can never be referenced from within the subclass.

Question 5

In Java subclass can only extend one parent class.

Question 6

The original class that is used to derive a new class using inheritance is called ____________________ .

A) a superclass
B) a parent class
C) a base class
D) all of the above
E) neither a, b, nor c

Question 7

If a subclasses constructor does not make an explicit call to a superclass's constructor, ______________________ .

A) a run-time error will result.
B) a compile-time error will result.
C) the constructor will be called anyway.
D) the class will be implicitly declared as abstract.
E) none of the above

Question 8

The derived class created using inheritace is called ______________________ .

A) a child class
B) a superclass
C) a parent class
D) all of the above
E) neither a, b, nor c

Question 9

A _______________________ class represents a generic concept in a class hierarchy.

A) super
B) abstract
C) interface
D) shadow
E) generic

Question 10

A child class is allowed to define a method with the same name and parameter list as a method in the parent class.

Question 11

Which of the following key words indicates a new class is being derived from an existing class?

A) super
B) final
C) extends
D) inherits
E) expands

Question 12

To invoke a parents constructor in a subclass, we use the ______________ method.

A) abstract
B) construct
C) parent
D) super
E) extends

Question 13

The process of inheritance should establish a(n) ___________________ relationship.

A) is-a
B) has-a
C) static
D) not-a
E) none of the above

Question 14

In order for derived classed to have access to encapsulated data members and methods of superclasses, the data members and methods should be declared using the ____________________ modifier.

A) private
B) public
C) protected
D) final
E) static

Question 15

When designing a class hierarchy, it is important that common features be ________________________ .

A) higher in the class hierarchy.
B) lower in the class hierarchy.
C) near the middle of the class hierarchy.
D) in abstract classes.
E) in the Object class.

Question 16

Which of the following methods are included in every class created in Java by inheritance?

A) next
B) toString
C) compareTo
D) charAt
E) none of the above

Question 17

Of the classes below, the one that is most likely to be declared abstract is _________________.

A) Bat
B) Squirrel
C) Animal
D) Iguana
E) Parrot

Question 18

All Java classes are subclasses of the ___________________ class.

A) String
B) java.lang
C) Java
D) Class
E) Object

Question 19

When a variable is declared in a subclass has the same name as a variable declared in a superclass, it is called a _______________ variable.

A) final
B) shadow
C) static
D) dead
E) this is not allowed in Java

Question 20

Java supports multiple inheritance.

Question 21

What is a shadow variable?

Question 22

What does it mean for a class to be declared as final? What does it mean for a method to be declared as final?

Question 23

Explain what it means for a child class to override a parent class. Why might this be useful?

Question 24

What is an abstract class, and why might it be useful in an inheritance hierarchy?

Question 25

Inheritance should not be considered in the software design process.

Question 26

Explain how a subclass can can access its parent classes private instance variables and methods.

Question 27

An abstract class must contain abstract methods.

Question 28

Explain the relevance of the Object class to the Java programming language.

Question 29

It is possible to derive a class from an abstract class without overriding all of the parents abstract methods.

Question 30

It makes sense to declare most abstract methods as final.

Question 31

Can a class be a parent of more than one subclass? Can a class be a child of more than one parent? Explain.

Question 32

A child class is allowed to declare a variable with the same name as one that is contained in the parent class.

Question 33

Explain why inheritance is useful.

Question 34

Describe the behavior of the toString method and the equals method of the Object class.

Question 35

Draw a hierarchy of Animals. The hierarchy should include the following entities: Animal, Reptile, Mammal, Bear, Human, Iguana, and Dolphin.

Question 36

A programmer tries to create a subclass of String called MyString. When the programmer compiles her new class, the compiler produces the following message:
MyString.java:1: cannot inherit from final java.lang.String
public class MyString extends String {
^
1 error
Explain the cause of this error.

Question 37

Consider an software system that will implement the following classes: Student, Professor, StaffMember, ContractWorker. List some common attributes of these classes. What would be a good abstract class from which these classes may be extended via inheritance?

Question 38

Suppose we create a subclass from a class that has a method called someMethod. If we override someMethod in the subclass, is it possible to access the superclass's version of someMethod? If so, how?

Question 39

Draw a hierarchy of people at a University.

Question 40

Compare and contrast the private visibility modifier to the protected visibility modifier. Why is the protected visibility modifier a better choice in an inheritance hierarchy?