Module 01-09 Introduction to Classes

Question 1

What are classes?

Answer 1

Classes serve as blueprints that indicate what variables and methods an object has.

Many individual objects with different variables and methods can be made from the same class.

Question 2

Variables and properties represent an object’s…

Answer 2

State

Question 3

Methods indicate an object’s

Answer 3

Behaviors

Question 4

How would you declare an instance of class Clock called clock?

Answer 4

Clock clock = new Clock();

Question 5

Private and Public are called…

Answer 5

Access modifiers.

They control visibility to methods and properties to the rest of your program.

Question 6

A derived property…

Answer 6

Lets you generate a value by relying on the other properties within the class.

A derived property is a getter that, instead of returning a member variable, returns a calculation taken from member variables. If we have firstName and lastName, we don’t need to also store fullName, we can derive it from what we already have.

Question 7

Methods are for when you need and object to…

Answer 7

do something! (perform a behavior)

Question 8

What does Encapsulation do?

Answer 8

Encapsulation lets you restrict access to the internal mechanism of how the class works by hiding or protecting its variables.

It’s the first pillar of object-oriented programming.

Question 9

What do methods with “void” method signatures return?

Answer 9

Nothing!

Question 10

What is a constructor?

Answer 10

A constructor is a special method that runs every time a new object is instantiated. It allows for the object to be initialized with a starting state.

It doesn’t return anything.
It must have the same name as the Class.
It can have arguments that set the value of member variables, like a Setter.
It can be Overloaded to provide multiple ways to instantiate the object.
If no constructor is present, then Java provides a default constructor, which has no arguments.

Question 11

Three Rules of an Overloaded Method

Answer 11

1. Overloaded methods must have the same name.
2. Overloaded methods must have the same return type (does not apply to constructors).
3. Overloaded methods must differ in the number of parameters and/or parameter types.

Question 12

What is Inheritance?

Answer 12

Inheritance is the practice of creating a hierarchy for classes in which descendants obtain the attributes and behaviors from other classes.

Question 13

What is Polymorphism?

Answer 13

Polymorphism is the ability for our code to take on different forms. In other words, we have the ability to treat classes generically and get specific results.

Question 14

All Reference Types are defined by a…

Answer 14

Class

Question 15

All Classes are defined by a…

Answer 15

Data Type

Question 16

True or False: Class name must match the file name

Answer 16

True.

Inside of Car.java file you have the class Car

Question 17

Classes should be named

Answer 17

with singular nouns or noun phrases in Pascal case (OneTwoThree)

Question 18

What do Member Variables (aka Instance Variables) do?

Answer 18

Member variables create object state. They should always be private.

Getters and Setters should be the only way to access member variables from outside the class.

Question 19

Getter and Setter methods should always begin with…

Answer 19

the “get” or “set” prefix, except for Getter methods that return a boolean, which should begin with the prefix “is”.

Question 20

The this keyword refers to…

Answer 20

the member variable specific to the instance of an object where the code is run.

Question 21

How do you declare a public method that takes a String and returns the String reversed?

Answer 21

public String reverser(String x)