This tutorial assumes that all you know is Java, but you want to learn Kotlin.
Please note that the resources are in the wiki page.
A few things that are worth watching to know more about Kotlin.
By me: Odd things to look out for when converting code to Kotlin
By me: Code clean-up with Kotlin
By me (newer article!): An opinionated guide on how to make your Kotlin code fun to read and joy to work with
Android KTX source code: Github snapshot or AOSP (actively developed)
inverted argument order, no semi-colons, void vs Unit, Object vs Any?, fun-Major-Syntax-Differences#inverted-argument-order-no-semi-colons-void-vs-unit-object-vs-any-fun)
interfaces with val, var and fun-Major-Syntax-Differences#interfaces-with-val-var-and-fun)
constructors, inheritance-Major-Syntax-Differences#constructors-inheritance)
lateinit vars-Major-Syntax-Differences#lateinit-vars)
enum class-Major-Syntax-Differences#enum-class)
annotation class-Major-Syntax-Differences#annotation-class)
final by default vs open-Major-Syntax-Differences#final-by-default-vs-open)
for loops (in ranges, until)-Major-Syntax-Differences#for-loops-in-ranges-until)
object for singleton-Major-Syntax-Differences#object-for-singleton)
statics via companion object, const val-Major-Syntax-Differences#statics-via-companion-object-const-val)
visibility in Kotlin (public by default, private, protected, internal)-Major-Syntax-Differences#visibility-in-kotlin-public-by-default-private-protected-internal)
static nested class in Java vs inner class in Kotlin-Major-Syntax-Differences#static-nested-class-in-java-vs-inner-class-in-kotlin)
backticks for reserved keywords (Mockito.when, $) and import aliases-Major-Syntax-Differences#backticks-for-reserved-keywords-mockitowhen--and-import-aliases)
is instead of instanceof, as and as? for casting-Major-Syntax-Differences#is-instead-of-instanceof-as-and-as-for-casting)
creating anonymous implementations for classes/interfaces-Major-Syntax-Differences#creating-anonymous-implementations-for-classesinterfaces)
there is no condition ? true : false ternary operator-Major-Syntax-Differences#there-is-no-condition--true--false-ternary-operator)
arrayOf and arrayOfNulls and listOf and mutableListOf and linkedMapOf-Major-Syntax-Differences#arrayof-and-arrayofnulls-and-listof-and-mutablelistof-and-linkedmapof)
array literals in annotations (for vararg parameters)-Major-Syntax-Differences#array-literal-in-annotations-even-for-single-argument-vararg-parameter)
operator conventions (get() vs [], .equals() vs ==)-Major-Syntax-Differences#operator-conventions-get-vs--equals-vs-)
there are no checked exceptions, try-with-resources as .use {}-Major-Syntax-Differences#there-are-no-checked-exceptions-use)
@Volatile and synchronized-Major-Syntax-Differences#volatile-is-replaced-with-volatile)
multiple generic bounds-Major-Syntax-Differences#multiple-generic-bounds)
typed nullability, and null-safety operators (?., ?:)-Basic-Kotlin-Features#typed-nullability-and-null-safety-operators--)
smart casting (and mutable vars gotcha)-Basic-Kotlin-Features#smart-casting-and-mutable-vars-gotcha)
lateinit vars-Basic-Kotlin-Features#lateinit-vars)
properties, backing fields-Basic-Kotlin-Features#properties-backing-fields)
string interpolation and """multiline escaped ${strings}"""-Basic-Kotlin-Features#string-interpolation-and-multiline-escaped-strings)
data classes-Basic-Kotlin-Features#data-classes)
when keyword (and complex conditions, such as ranges)-Basic-Kotlin-Features#when-keyword)
control statement as expression (assignment of when, return, ...)-Basic-Kotlin-Features#control-statement-as-expression-assignment-of-when-return)
named arguments, default arguments-Basic-Kotlin-Features#named-arguments-default-arguments)
vararg and the * spread operator-Basic-Kotlin-Features#vararg-and-the--spread-operator)
interfaces and default implementation-Basic-Kotlin-Features#interfaces-and-default-implementation)
generics (<T: Blah>, in/out, and star projection <*>)-Basic-Kotlin-Features#generics-t-blah-inout-and-star-projection-)
lambda types, trailing lambdas-The-Cool-Stuff#lambda-types-trailing-lambdas)
method reference-The-Cool-Stuff#method-reference)
typealias-The-Cool-Stuff#typealias)
lambdas with receivers-The-Cool-Stuff#lambdas-with-receivers)
extension functions, extension properties-The-Cool-Stuff#extension-functions-extension-properties)
standard library functions - scoping functions: apply, let, also, run, with-The-Cool-Stuff#standard-library-functions---scoping-functions-apply-let-also-run-with)
standard library functions - more utility functions: takeIf, takeUnless-The-Cool-Stuff#standard-library-functions---more-utility-functions-takeif-takeunless)
tailrec keyword-The-Cool-Stuff#tailrec-keyword)
inline functions (crossinline, noinline)-The-Cool-Stuff#inline-functions-crossinline-noinline)
*a glance at the Collections API-The-Cool-Stuff#a-glance-at-the-collections-api) (see API here)
inline fun <reified T>-The-Cool-Stuff#inline-fun-reified-t)
sealed classes-The-Cool-Stuff#sealed-classes)
infix keyword-The-Cool-Stuff#infix-keyword)
tuples (to) and destructuring-The-Cool-Stuff#infix-keyword)
*extension operators (componentN)-The-Tricky-Stuff#extension-operators-componentn)
*property delegates (and built-in ones: lazy, observable/vetoable, by map for configurations via Map<String, Any?>)-The-Tricky-Stuff#property-delegates-and-built-in-ones-lazy-observablevetoable-by-map-for-configurations-via-mapstring-any)
delegation by class-The-Tricky-Stuff#delegation-by-class)
*JVM annotations: @JvmOverloads, @JvmField, @JvmSuppressWildcards, @get: and @set: and @field:-The-Tricky-Stuff#jvm-annotations-jvmoverloads-jvmfield-jvmstatic-jvmsuppresswildcards-get-and-set-and-field)
synthetic view accessors with kotlin android extensions (deprecated)-Android-Specific-Stuff#synthetic-view-accessors-with-kotlin-android-extensions)
@Parcelize data class with experimental kotlin android extensions-Android-Specific-Stuff#parcelize-data-class-with-experimental-kotlin-android-extensions)
Coroutines, coroutines on Android, suspend fun
Channels: LinkedListChannel, BroadcastChannel
@DslMarker
multi-platform things: expect and actual
contracts
Copyright 2018-2020 Gabor Varadi
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