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Basic Types
Hello World Basic Types Variables Functions Collections Branches and Loops Classes Properties Visibility Scope Abstract Classes and Interfaces Object Nested Objects and Classes Enums and Sealed Classes Generics Exceptions Nullability Scope Functions Functional Programming Sequence Extension Functions Delegates Coroutine Basics Flows and Channels Advanced Syntax
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As with Java, a character literal is a single character surrounded by apostrophes (').

You can learn more about this in:

the documentation
Elements of Kotlin

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Characters

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Kotlin/JS 1.4.32 with Coroutines 1.4.3

Abstract Classes
Abstract val Custom Getter
Abstract val Properties
Abstract var

Anonymous Functions
Anonymous Functions as Parameters
return and Anonymous Functions

Accessing Elements via []
Array Modification
Arrays
filter()
for Loop
forEach()
forEach() is a Function
map()
map() Type Conversions
Typed Arrays

async()

break Statements
Capturing Values in when
continue Statements
else if
if
if as an Expression
if as an Expression, Using Blocks
if Without else
Single-Line if
when
when as an Expression
when with Commas
when with Expressions for Branches
when with Ranges
when Without an Expression
when Works with Any Type
while

A Conflated Channel
A Fixed-Buffer Channel
A Simple Channel
A Zero-Buffer Channel
BroadcastChannel
Channel and receive()
Channels and Fan-out
Hot Channels Via offer()
The Channel() Function
toList() for Channel

Characters

Accessing Elements via []
any()
any() and Short Circuits
Array Modification
Arrays
Combining Collections
filter()
first()
first() Sans Lambda
firstOrNull()
firstOrNull() and the Elvis Operator
fold()
for Loop
forEach()
forEach() is a Function
joinToString()
Lists
map()
map() Type Conversions
Maps
Mutable Lists
Sets
Typed Arrays

Companion Objects
Companion Objects and Private Members
Named Companion Objects

Classes and Instances
Constructor Init-Only Parameters
Constructors
Formal Constructor Declaration
Inheritance and Constructors
Init Block
Secondary Constructors

cancelAndJoin()
Canceling a Job
Canceling a Parent Cancels Its Children
Canceling and Cooperation
Cooperation by Checking isActive
Cooperation by Yielding
Jobs Cancel When They Crash
Non-Cancellable Coroutines
Parent Jobs Cancel When a Child Crashes

Abstract val Custom Getter
Abstract var
Custom Accessor Parallelism
Custom Accessors and the Field
Custom Getter Functions
Custom Setter Functions
Inline Custom Getter Functions

Class Delegates

Destructuring Declarations
Destructuring Declarations and Lambdas
Destructuring Declarations of Maps

Elvis Returns!
The Elvis Operator

enum and Functions
enum and when()
enum Class
enum name and ordinal
enum valueOf()
enum values()

Content and Instance Equality

Custom Exception Classes
Exceptions
Exceptions and the Call Stack
Jobs Cancel When They Crash
Multiple catch Blocks
Parent Jobs Cancel When a Child Crashes
Throwing Exceptions
try and catch
try as an Expression

Extension Functions
Extension Functions on Nullable Types
Private Extension Functions

Extension val Property
Extension var Property

Assigning Function Results
Chaining to Superclass Functions
Default Parameter Values
Expression Bodies
Expression Bodies and Return Types
Functions with Parameters
Functions with Return Types
Hello, World! (In a Function)
Infix Functions
Inheritance and Functions
Inheritance and Overriding Functions
Local Variables
Named Parameter Values
override is Transitive
Spread Operator
Spread Operator with Primitive Types
Values for Varargs
Varargs

any()
any() and Short Circuits
Chaining Higher-Order Functions
first()
first() Sans Lambda
firstOrNull()
firstOrNull() and the Elvis Operator
fold()
Function Reference
Function Reference for Member Functions
Function References and Receivers
Function Types
Function Types and Direct Invocation
Function Types and Parameters
Functional Interfaces
joinToString()
Type Aliases

Adding Functions to Classes

Nullable Generic Types
Nullable Generic Types, Continued

As Generic As You Want
Generics
Generics and Supertypes
Generics and Upper Bounds
Implied Generic Type
Reified Types
Your Own Generic Classes

Hello, World! (In a Class)
Hello, World! (In a Function)

else if
if
if as an Expression
if as an Expression, Using Blocks
if Without else
Single-Line if

Chaining to Superclass Functions
Checking Inheritance Via is
Inheritance
Inheritance and Constructors
Inheritance and Functions
Inheritance and Overriding Functions
is and when
Manual Casts
override is Transitive
Overriding Properties
Smart Casts

Infix Functions
Inline Functions
Inline Properties
Reified Types

Interfaces
Multiple Interfaces

Contexts and Jobs
Jobs and Parents

Lambda Expressions
Lambda Expressions and Parameters

Accessing Elements via []
Combining Collections
filter()
for Loop
forEach()
forEach() is a Function
Lists
map()
map() Type Conversions
Mutable Lists

Accessing Elements via []
Combining Collections
for Loop
forEach()
forEach() is a Function
Maps

Basic Math

Nothing As a Return Type

Elvis Returns!
Functions on Nullable Types
Nullable Casts
Nullable Casts, Continued
Nullable Generic Types
Nullable Generic Types, Continued
Nullable Types
Safe Call Chains
Safe Calls
Smart Contracts
The Elvis Operator

Basic Math
Printing the Class of Numbers
Using Underscores for Thousands Separators

Companion Objects
Companion Objects and Private Members
Manual Singletons
Named Companion Objects
Named Nested Objects
Object Properties
Object Singletons
Objects and Superclasses

Augmented Assignments
Increment and Decrement Operators
Unary Operators

invoke() Operator
Operator Overloading

Default Parameter Values
Functions with Parameters
Named Parameter Values

promise()

Adding Properties to Classes
Passing this as a Parameter
The this Pseudo-Property

Abstract val Custom Getter
Abstract val Properties
Abstract var
lateinit Properties
lazy Properties
Overriding Properties
Property Initialization in Declaration
Property Initialization in Init Block

Delegates.observable()
Delegates.vetoable()
lazy Properties
Map as a Property Delegate

Reified Types

Custom Labels
Default return Behavior
Labeled Returns
return and Anonymous Functions

Safe Call Chains
Safe Calls

Block-Local Scope
Function-Local Scope
Instance Scope

also()
apply()
apply() Return Value
let()
let() Return Value
run()
run() and Safe Calls
with()

Non-Nested Sealed Classes
Sealed Classes
Sealed Classes and when

generateSequence()
Sequences and sequenceOf()

filter()
for Loop
forEach()
forEach() is a Function
map()
map() Type Conversions
Sets

Raw Strings
String Concatenation
String Interpolation
String Interpolation with Expressions
trimMargin()

Read-Only Variables
Type Conversions
Variables and Operators
You Cannot Modify Read-Only Variables

Augmented Assignments
Increment and Decrement Operators
Type Conversions
Typed Variables
Variables
Variables and Operators
You Can Modify Normal Variables

private Members
protected Members

Capturing Values in when
enum and when()
when
when as an Expression
when with Commas
when with Expressions for Branches
when with Ranges
when Without an Expression
when Works with Any Type

break Statements
continue Statements
while