Beginner's Guide to Kotlin Programming

Preface
Chapter Organization
What You Need
Using an IDE
Downloading the IntelliJ IDEA IDE
Conventions
Example Code and Sample Solutions
Contents
1 Introduction
What is Kotlin?
Kotlin Versions
Kotlin Programming
Kotlin Libraries
Kotlin Execution Environment
Where is Kotlin Used
Kotlin JVM Environment
Kotlin Documentation
Running Kotlin Programs
Interactively Using the Kotlin REPL Interpreter
Running a Kotlin File
Executing a Kotlin Script
Using Kotlin in an IDE
Useful Resources
Part I Kotlin Programming
2 A First Kotlin Program
Introduction
Hello World
Setting up Your Program
Starting up Kotlin
Create a New Kotlin File
Create the Main Function
Interactive Hello World
Variables
Vals and Vars
String Formatting
Naming Conventions
Assignment Operator
Kotlin Statements and Expressions
Comments in Code
Basic Types
Unsigned Integer Types
Numeric Conversions
Online Resources
Exercises
3 Flow of Control
Introduction
Operators
Comparison Operators
Logical Operators
Numeric Operators
Assignment Operators
The if Statement
Working with an if Statement
Else in an if Statement
The Use of Else If
Kotlin if Expression
Nesting if Statements
Null and Conditional Statements
Explicitly Checking for Null Conditions
The Safe Call Operator
The Elvis Operator
The Not-Null Assertion Operator
Smart Compilation
Safe Casting to Non Null Type
When Expression
While Loop
Do Loop
For Loop
Repeat Loops
Loop Control Statements
Break Loop Statement
Continue Loop Statement
When with Continue and Break
A Note on Loop Variable Naming
Dice Roll Game
Online Resources
Exercises
Check Input is Positive or Negative
Test if a Number is Odd or Even
Kilometres to Miles Converter
Calculate the Factorial of a Number
4 Number Guessing Game
Introduction
Setting Up the Program
What Will the Program Do?
Creating the Game
Generate the Random Number
Obtain an Input from the User
Check to See if the Player Has Guessed the Number
Check They Haven't Exceeded Their Maximum Number of Guess
Notify the Player Whether Higher or Lower
End of Game Status
The Complete Listing
Hints
Blank Lines Within a Block of Code
Exercises
5 Functions in Kotlin
Introduction
What Are Functions?
Defining Functions
An Example Named Function
Function Parameters
A Function with Parameters
Multiple Parameter Functions
Default Parameter Values
Named Arguments
Arbitrary Number of Arguments
Parameters Are Vals
Returning Values from Functions
Anonymous Functions
Single Expression Functions
Lambdas
Lambdas Versus Anonymous Functions
Recursive Functions
Calculating Factorial Recursively
Tail Recursion Optimisation
Inline Functions
Online Resources
Exercises
Calculate Prime Numbers
Adding Functions to the Number Guess Game
6 Higher Order Functions
Introduction
Recap on Functions in Kotlin
Functions as Entities
Box Operator
Higher Order Function Concepts
Higher Order Function Example
Higher Order Functions and Lambdas
Using Higher Order Functions
Functions Returning Functions
Online Resources
Exercises
7 Curried Functions
Introduction
Currying Concepts
Kotlin and Curried Functions
Closure
Online Resources
Exercises
Part II Object-Oriented Kotlin
8 Kotlin Classes
Introduction
Classes
What are Classes for?
What Should a Class Do?
Class Terminology
Classes Versus Instances
Class Definitions
Working with the Class Person
Be Careful with Assignment
Working with Properties
Accessing Member Properties
Using String Templates
Updating Properties
Classes and Constructors
Simplifying the Class Person
Primary Constructors
Defining Default Constructor Parameters
Named Constructor Parameters
Private Properties
Auxiliary Constructors
Initialisation Behaviour
Defining Instance Behaviour
Writing Member Functions
Member Functions with Parameters
Member Functions Returning Values
Parameters Are Vals
Named Member Function Parameters
Default Parameter Values
Variable Parameter Lists
The This Reference
Referencing Member Functions
Single Expression Member Functions
Defining a Default String Representation
Providing KDoc
Equality Between Instances
Automatic Memory Management
Class Design Considerations
Online Resources
Exercises
9 Objects and Companion Objects
Introduction
Singleton Objects
Singleton Objects in Kotlin
Anonymous Objects
Companion Objects
Companion Object Behaviour
An Object or An Instance
Online Resources
Book References
Exercises
10 Further Kotlin Properties
Introduction
Property Declarations
Types Held by a Property
Top Level Properties
Constructor Parameters
Member Level Properties
Property Visibility
Property Declaration Modifiers
Applying const to val Properties
Applying lateinit to var Properties
Applying Lazy Initialisation to val Properties
Summary
Creating Custom Property Setters and Getters
Using an Implicit Backing Field
Using an Explicit Backing Field
Properties Without a Backing Field
Modifying Setter Visibility
GameObject with Properties
Online Resources
Exercises
11 Scope and Conditional Functions
Introduction
The User Class
The Apply Scope Function
The Also Scope Function
The Run Scope Function
The Let Scope Function
The with Scope Function
Scope Functions and Nullability
Scope Function Categories
Conditional Functions
Exercises
12 Class Inheritance
Introduction
What is Inheritance?
Terminology Around Inheritance
Types of Hierarchy
Purpose of Subclasses
Kotlin Class Hierarchy
Kotlin Classes and Inheritance
Objects and Inheritance
Anonymous Objects and Inheritance
The Class Any and Inheritance
Inheritance and Member Functions
Overriding Member Functions
Declaring Member Functions as Open
Inheritance and Properties
Extending Behaviour Using Super
Casting and Inheritance
Smart Casting
Checking the Type
Explicit Casts
Safe Casts
Closing a Member
Closing Member Functions
Closing Properties
Inheritance Summary
Online Resources
Exercises
13 Abstract Classes
Introduction
Abstract Classes as a Concept
Abstract Classes in Kotlin
Defining an Abstract Class and Member Functions
Subclassing an Abstract Class
Abstract Properties
Abstract Subclasses
Online Resources
Exercises
14 Interfaces, Delegation and Enumerated Types
Introduction
Kotlin Interfaces
Defining an Interface
Implementing an Interface
Objects Can Implement Interfaces
Extending a Class and Implementing Interfaces
Inheritance by Interfaces
Interfaces and Concrete Member Functions
Multiple Interfaces with the Same Concrete Member Functions
Interface Companion Objects
Marker Interfaces
Delegation
Enumerated Types
Kotlin Enums
Ordering Enumerated Type
Providing Additional Enum Data
Online Resources
Exercises
15 Packages
Introduction
Packages
Declaring a Package
How Packages Relate to Directories
Finding a Package
Importing a Package
Using the Fully Qualified Name
Importing a Type, Function or Property
Import Options
Dealing with Name Clashes
Kotlin Default Imports
Visibility Modifiers
Visibility Modifiers and Constructors
Online Resources
Exercise
16 Nested/Inner Types
Introduction
What are Nested/Inner Types
Nested Types
Member Inner Classes/Anonymous Objects
Member Function Inner Classes/Objects
Function Inner Classes/Objects
Online Resources
Exercise
17 Data Classes
Introduction
Defining Data Classes
Data Classes with Non Constructor Properties
Data Classes and Inheritance
Data Classes and Interfaces
Copying Data Classes
Data Classes and De-structuring
Exercise
18 Sealed and Inline Classes and Typealias
Introduction
Sealed Classes
Sealed Classes in Kotlin 1.4
Sealed Classes and Interfaces in Kotlin 1.5
Inline Classes
Inline Class Constraints
Simple Inline Class Example
Additional Inline Class Concepts
Typealias
19 Operator Overloading
Introduction
Why Have Operator Overloading?
Why Not Have Operator Overloading?
Implementing Operator Overloading
Overloading the Operator Member Functions
Mutable Data Types
Numerical Operators
Unary Prefix Operators
Postfix Increment and Decrement Operators
Comparison Operators
Augmented Assignment Operators
Containment (in) Operators
Infix Named Operators
Summary
Online Resources
Exercises
20 Error and Exception Handling
Introduction
Errors and Exceptions
What is an Exception?
What Is Exception Handling?
Handling an Exception
Multiple Catch Blocks
Accessing the Exception Object
Jumping to Exception Handlers
The Finally Clause
Throwing an Exception
Try Catch as an Expression
Defining an Custom Exception
Chaining Exceptions
Nesting Exception Handlers
Limitations of Try-Catch
Functional Exception Handling
Accessing the Failure Exception
Accessing the Successful Value
Treating Result as a Container
Recovery Operations
Providing Explicit OnFailure and OnSuccess Behaviour
Online Resources
Exercises
21 Extension Functions and Properties
Introduction
Extensions
Extension Functions
Extension Properties
Infix Extension Operators
Extensions Scope
Online Resources
Exercises
Part III Data Containers
22 Arrays
Introduction
Kotlin Arrays
Creating Arrays
Using Class Array
Using Specialised Array Classes
Using Factory Function arrayOf
Specialised arrayOf Functions
Create Empty Arrays
Create an Array of Different Types
Working with Arrays
Arrays of Reference Types
Working with Primitive Type Arrays
Working with User Defined Types
Iteration and Arrays
Iterating Over an Array
Iterating Over the Indices for an Array
Multi-Dimensional Arrays
Ragged Arrays
Array Operations/Functions
23 Collections
Introduction
Collections Library
Kotlin Collection Types
24 Lists
Introduction
Lists
List Creation
Using Classes Directly
Using Factory Functions
Nested Lists
Accessing List Data
Obtaining the Size of a List
Accessing Elements from a List
Updating Elements Using an Index
Obtaining a Slice or Sub List
Adding to a List
Inserting Into a List
List Concatenation
Removing from a List
Checking for List Membership
Iterating Over Lists
List Member Functions
Online Resources
Exercises
25 Sets
Introduction
Sets
Creating Sets
Set Properties and Member Functions
Accessing Elements in a Set
Working with Sets
Checking for Presence of an Element
Adding Items to a Set
Removing an Item
Nesting Sets
Set like Operations
Online Resources
Exercises
26 Maps
Introduction
Maps
Creating a Map
Map Properties
Working with Maps
Accessing Items via Keys
Adding a New Entry
Changing a Keys Value
Removing an Entry
Values, Keys and Items
Iterating Over Keys
Iterating Over Values
Iterating Over Map Entries
Checking Key Membership
Nesting Dictionaries
Online Resources
Exercises
27 Pairs and Triples
Introduction
Creating Pairs and Triples
Creating Pairs
Creating Triples
Working with Pairs and Triples
Accessing Elements of a Pair or Triple
Copying Pairs and Triples
Converting Pairs and Tiples to Lists
Destructuring Pairs and Triples
Nested Pairs and Triples
Things You Can’t Do with Pairs and Triples
Exercises
28 Generic Types
Introduction
The Generic Set Class
Writing a Generic Type
Declaration-Site Variance
Generic Functions
Generic Constraints
Creating a Parameterised Type
Exercises
29 Functional Programming and Containers
Introduction
ForEach
Filter
Map
Flatten
FlatMap
Sorting Iterables
Fold
FoldRight
Reduce
Labelled Return from Lambdas
Online Resources
Exercises
Part IV Concurrent Kotlin
30 Coroutines
Introduction
Concurrency
Parallelism
Threads
The Problems with Threads
Coroutines Introduction
Working with Coroutines
Adding Coroutine Library Dependencies
Implementing a Coroutine
Launching Coroutines
Suspending Functions
Running Multiple Concurrent Coroutines
Coroutine Scope
Custom Coroutine Scope
Coroutine Dispatchers
Coroutine Builders/Launchers
Coroutine Jobs
Online Resources
Exercise
31 Coroutine Channel Communications
Introduction
Coroutine Channels
Rendezvous Channel
Buffered Channel
Unlimited Buffered Channel
Conflated Channel
Multiple Senders and Receivers
Multiple Coroutine Channel Senders
Multiple Coroutine Channel Receivers
Pipelines
Exercise
Part V Android Development
32 Android Overview
Introduction
What is Android?
Android Versions
Android Programming Languages
Android Runtime
Deploying to Android
Packaging an Application
Application Core Building Blocks
Core Element Types
How Core Elements Fit Together
Android JetPack
Online Resources
33 Applications and Activities
Introduction
Android Studio
Setting Up a Project
Android SDKs
Android Studio AVD
Creating an Android Application
Creating a New Project
Run the Application
Android Application
Basic Application Structure
Gradle Build Files
Actual Directory Structure
HelloWorld Application
Online Resources
34 Android Layouts and Events
Introduction
Activity Uses Layouts
Views
View Layouts
View Hierarchy
View Layout Options
Linear Layout
Constraint Layout
Containers
Creating Displays
Working with the Layout Editor
Programmatically Creating Layout
Interacting with the Application
Event Generation
View Handler Architecture
Shortcut OnClick Resource
Online Resources
35 Android Tic Tac Toe
Introduction
Classes in the Game
Counter Class
Move Class
The Player Class
The ComputerPlayer Class
The Board Class
The MainActivity Class
The Screen Layout
Running the Game