Ch.11

Question 1

What is Inheritance?

Answer 1

Defining a new class by extending an existing class. (like child class from parent class)

Question 2

What is a Superclass?

Answer 2

AKA “parent class”,
A general class that can be used to create specialized classes (subclasses).

Question 3

What is a Subclass?

Answer 3

AKA “child class”,
A specialized class that is created using a general class (Superclass).

Question 4

What are Subtypes and Supertypes?

Answer 4

Ex: Circle is “subtype” of GeometricObject,
GeometricObject is “supertype” for Circle.

Question 5

How do you write the class declaration for a Subtype?

Answer 5

public class Subclass extends Superclass

Question 6

Is it possible to change parent/supertype data fields from the child/subtype class?

Answer 6

Yes, using the parent/supertype’s public methods: getter/setter/etc

Question 7

Multiple Inheritance

Answer 7

Capability NOT ALLOWED BY JAVA.
Means a subclass can be derived from multiple classes.

Question 8

Single Inheritance

Answer 8

Restriction only allowing a subclass to be derived from a single superclass.

Question 9

“super” Keyword

Answer 9

Refers to the superclass of the class the keyword appears in. Used to call the superclass constructor and reference superclass’s accessible(public) members.

Question 10

Calling Superclass Constructors from Subclass

Answer 10

Superclass constructors aren’t inherited by a subclass. They can only be invoked by subclass constructors using keyword ‘super’.
Ex: super() or super(arguments);

Question 11

What Superclass Constructor is invoked automatically by a Subclass Constructor?

Answer 11

The Superclass Default Constructor.
super();

Question 12

Why should every class contain a no-arg/default constructor?

Answer 12

It’s easier to extend the class and avoid errors with reuse.

Question 13

What constructor does a subclass invoke first?

Answer 13

The superclass constructor.
If that superclass is derived from its own superclass, then that ‘ancestor’ class would be invoked first.

Question 14

Constructor Chaining

Answer 14

A subclass invokes its superclass’s constructor before it performs other tasks.
If that superclass has its own superclass, then that parent class would also invoke the parent class before doing its own functions.

Question 15

Calling Superclass Methods

Answer 15

super.method(arguments);

Question 16

Overriding Superclass Method in Subclass

Answer 16

Method must be defined in subclass with same signature as superclass. This only goes for accessible/public superclass methods.

Question 17

Static Methods

Answer 17

Static methods cannot be overridden. If Superclass and Subclass define the same static method, then the superclass’s is hidden unless specifically invoked:
SuperClassName.staticMethodName.

Question 18

Method Overriding

Answer 18

Subclass modifies implementation of method defined in superclass.

Question 19

Overload vs Override

Answer 19

Override has the same signature, Overload has the same function name, but different parameter list.

Question 20

Polymorphism

Answer 20

Supertype variable can refer to a subtype object.

Question 21

Dynamic Binding

Answer 21

An object’s class will be determined at runtime, like in the case of the toString() example.

Question 22

Casting Object

Question 23

Create Array List from an Array

Answer 23

ArrayList<array_type> list = new ArrayList<>(Arrays.asList(array))</array_type>

Question 24

Create Array from an Array List

Answer 24

type[] array = new type[list.size()];
list.toArray(array1);