Unit 9 - Inheritance

Question 1

Superclass

Answer 1

Class hierarchy can be developed by putting common attributes & behaviors of related classes into a single class

Question 2

Subclasses

Answer 2

Extend a superclass
Can draw upon existing attributes & behaviors of superclass without repeating in code

Question 3

Extending a subclass from a superclass creates an

Answer 3

"is-a" relationship from subclass to superclass
(Lower class) is a (Upper class)

Question 4

Inheritance

Answer 4

Parent classes have attributes & behaviors that can be inherited by child classes

Question 5

Why use inheritance

Answer 5

Code reusability
Prevents repeating code
Readability & organization
Ease of maintenance

Question 6

Each subclass can only have

Answer 6

one superclass

Question 7

All subclasses inherit

Answer 7

attributes and methods of their superclasses

Question 8

A superclass can’t

Answer 8

inherit attributes and methods of subclass implicitly

Question 9

keyword extend

Answer 9

Used to establish an inheritance relationship between subclass and a superclass
Can only extend one superclass

Question 10

Constructors are

Answer 10

NOT inherited

Question 11

When a subclass’s constructor does not explicitly call a superclass’s constructor using super,

Answer 11

Java inserts a call to superclass’s no-argument constructor

Question 12

Superclass constructor can be called from first line of subclass constructor by using

Answer 12

keyword super and passing appropriate parameters

Question 13

Actual parameters passed in call to superclass constructor provides

Answer 13

values that constructor can use to intialize the object’s instance variabes

Question 14

Using super will call

Answer 14

No-argument constructor of superclass
MUST be the first line of body of constructor

Question 15

Whether superclass constructor is called implicitly or explicitly, process of calling superclass constructors continue up

Answer 15

inheritance hierarchy with each constructor calling constructor of superclass until Object constructor is called

Question 16

Method overriding occurs when

Answer 16

a public method in a subclass has the same method signature as a public method the superclass

Question 17

Any method that is called must be defined withint tis

Answer 17

own class or superclass

Question 18

Subclass is usually designed to have

Answer 18

modified or additional methods or instance variables

Question 19

Subclass inherit all

Answer 19

public methods of superclass and will remain public in subclass

Question 20

What are options with methods when we extend a superclass?

Answer 20

Inherit methods
Write new methods
Override methods

Question 21

Inherit methods

Answer 21

Public methods in superclass become valid public methods of subclass
Important to acces private instance variables

Question 22

Write new methods

Answer 22

Additional methods completely independent of methods in superclass
Includes overloaded methods and treated as independent methods

Question 23

Override methods

Answer 23

Write a new or different implementation of a method that already exists in superclass

Question 24

keyword super

Answer 24

Can be used to call superclass’s constructors and methods

Question 25

Superclass method can be called in a subclass by using

Answer 25

keyword super with method name and passing appropriate parameters

Question 26

Subclass

Answer 26

Class that extends another class

Question 27

Superclass

Answer 27

Class being extended

Question 28

Polymorphic reference variable

Answer 28

Can refer to objects from different classes at different points in code
Can store a reference to its declared class or tan any subclass of its declared class

Question 29

Why would we declare a variable using a superclass if we plan to store a reference to a subclass object?

Answer 29

A collection needs to be declared as a data type

Question 30

If s is a subclass of T, then assigning an object of type s to a reference of type t facilitates

Answer 30

polymorphism

T obj = new S(arguments)

Question 31

If s is a subclass of T, then a reference of type T can be used to refer to

Answer 31

An object of type T or S

Question 32

Declaring references of type T when s is a subclass of T is useful in followin declarations

Answer 32

Formal method parameters

Arrays T[ ] var or ArrayList ,T> var

Question 33

Method is considered polymorphic when it is

Answer 33

overridden in at least one subclass

Question 34

Polymorphism

Answer 34

Act of executing an overridden non-static method from correct class at runtime based on actual object type

Question 35

Object superclass

Answer 35

Superclass of all other classes in Java

Question 36

When a class does not expliciting extend another class, then

Answer 36

it implicitly extends Object

Question 37

Subclasses of Object often

Answer 37

override the equals and toString methods with class specific implementations

Question 38

When an object is passed as a parameter to the print() or println() method,

Answer 38

object’s toString() method is implicitly called