Inheritance

Question 1

The process of creating derived classes from a base class to enhance code reusability.

Answer 1

Inheritance

Question 2

Inheritance relationship can be described as

Answer 2

superclass-subclass
is-a/an, is-a-kind-of
has-a

Question 3

the “is-a” rule states that __________ of the subclass is an object of the superclass

Answer 3

every object

Question 4

You can use a subclass object whenever the program expects a superclass.

Answer 4

Substitution Principle

Question 5

What features can be inherited by the subclass?

Answer 5

Public and Protected

Question 6

The super constructor must always be the ____________ in another constructor.

Answer 6

first statement

Question 7

The collection of classes extending from a common superclass is called an ________________________

Answer 7

Inheritance Hierarchy

Question 8

The path from a particular class to its ancestor is its ______________________.

Answer 8

Inheritance chain

Question 9

When some methods in superclass is not appropriate for the subclasses, the solution is to _________________________

Answer 9

override methods

Question 10

When designing Classes, place the _______________ in the superclass

Answer 10

general methods

Question 11

Place the more ______________ in the subclass(es)

Answer 11

specialized methods

Question 12

Subclasses are more superior because they have more functionality than superclasses

Answer 12

TRUE

Question 13

Benefits of Inheritance

Answer 13

• Forms ranking or ordering of abstractions
• Simplifies our understanding of a problem
• Allows code reuse

Question 14

Java employs _______ inheritance

Answer 14

Single

Question 15

top of hierarchy

Answer 15

java.lang.Object

Question 16

All classes in the Java Platform are descendants of the _____________

Answer 16

Object class

Question 17

user within the subclass to refer to its superclass, or to invoke constructor, method or attribute (discouraged) of the super class.

Answer 17

Super keyword

Question 18

constructors are not inherited.

Answer 18

TRUE

Question 19

Redeclaring and redefining a method of the superclass in the subclass

Answer 19

Method Overriding

Question 20

In overriding a method, the _____ and _________ (name, parameter types) should be the same as the original method

Answer 20

return type, method signature

Question 21

When overriding a method, the access modifier should be the same or less strict.

Answer 21

TRUE

Question 22

Given the method:

int add (int x, int y);

is the method overriding:

protected int add (int a, int b);

valid?

Answer 22

YES, from default to a less strict access modifier (protected)

Question 23

With ___________ keyword, there is no need to implement the method (no method body required)

Answer 23

Abstract

Question 24

For added clarity, a class with one or more abstract methods must itself be declared abstract

Answer 24

TRUE

Question 25

Other than the abstract methods, an abstract class can have attributes and
concrete methods, just like any normal class

Answer 25

TRUE

Question 26

are classes designed to become superclasses

Answer 26

Abstract Classes

Question 27

TRUE or FALSE:

You can instantiate abstract classes.

Answer 27

FASLE

Question 28

TRUE or FALSE:

When a method is abstract in the superclass, the subclass has the option not to override it.

Answer 28

FALSE. All abstract methods from the superclass must be overridden by the derived class.

Question 29

are classes designed to be leaf nodes in
the hierarchy. That is, final classes cannot be extended.

Answer 29

Final Classes

Question 30

________________
cannot be overridden by the
subclasses

Answer 30

Final methods

Question 31

Problems of Inheritance

Answer 31

Yoyo Problem
* When understanding the behavior of an object whose
class comes from a hierarchy, we might have to go up
and down the hierarchy to trace the behavior.

Dependency Problem
* Stability and existence of a subclass demands the
same from a superclass.
* Therefore when “transporting” a superclass B, it must
be transported with its superclasses.

Size and Efficiency Problem
* Note that subclasses are actually larger than their
superclasses (although they might appear to be
written with less code).
* Sometimes, not all inherited methods are required in a
given problem.
* It does save us programming time but performance
may suffer when dealing with larger than required
objects.
* Therefore, inheritance trees should be as shallow as possible.