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1# kotlinx.coroutines
2
3[![Kotlin Stable](https://kotl.in/badges/stable.svg)](https://kotlinlang.org/docs/components-stability.html)
4[![JetBrains official project](https://jb.gg/badges/official.svg)](https://confluence.jetbrains.com/display/ALL/JetBrains+on+GitHub)
5[![GitHub license](https://img.shields.io/badge/license-Apache%20License%202.0-blue.svg?style=flat)](https://www.apache.org/licenses/LICENSE-2.0)
6[![Download](https://img.shields.io/maven-central/v/org.jetbrains.kotlinx/kotlinx-coroutines-core/1.6.4)](https://search.maven.org/artifact/org.jetbrains.kotlinx/kotlinx-coroutines-core/1.6.4/pom)
7[![Kotlin](https://img.shields.io/badge/kotlin-1.6.21-blue.svg?logo=kotlin)](http://kotlinlang.org)
8[![Slack channel](https://img.shields.io/badge/chat-slack-green.svg?logo=slack)](https://kotlinlang.slack.com/messages/coroutines/)
9
10Library support for Kotlin coroutines with [multiplatform](#multiplatform) support.
11This is a companion version for the Kotlin `1.6.21` release.
12
13```kotlin
14suspend fun main() = coroutineScope {
15    launch {
16       delay(1000)
17       println("Kotlin Coroutines World!")
18    }
19    println("Hello")
20}
21```
22
23> Play with coroutines online [here](https://pl.kotl.in/hG_tKbid_)
24
25## Modules
26
27* [core](kotlinx-coroutines-core/README.md) — common coroutines across all platforms:
28  * [launch] and [async] coroutine builders returning [Job] and [Deferred] light-weight futures with cancellation support;
29  * [Dispatchers] object with [Main][Dispatchers.Main] dispatcher for Android/Swing/JavaFx, and [Default][Dispatchers.Default] dispatcher for background coroutines;
30  * [delay] and [yield] top-level suspending functions;
31  * [Flow] — cold asynchronous stream with [flow][_flow] builder and comprehensive operator set ([filter], [map], etc);
32  * [Channel], [Mutex], and [Semaphore] communication and synchronization primitives;
33  * [coroutineScope][_coroutineScope], [supervisorScope][_supervisorScope], [withContext], and [withTimeout] scope builders;
34  * [MainScope()] for Android and UI applications;
35  * [SupervisorJob()] and [CoroutineExceptionHandler] for supervision of coroutines hierarchies;
36  * [select] expression support and more.
37* [core/jvm](kotlinx-coroutines-core/jvm/) — additional core features available on Kotlin/JVM:
38  * [Dispatchers.IO] dispatcher for blocking coroutines;
39  * [Executor.asCoroutineDispatcher][asCoroutineDispatcher] extension, custom thread pools, and more.
40* [core/js](kotlinx-coroutines-core/js/) — additional core features available on Kotlin/JS:
41  * Integration with `Promise` via [Promise.await] and [promise] builder;
42  * Integration with `Window` via [Window.asCoroutineDispatcher], etc.
43* [test](kotlinx-coroutines-test/README.md) — test utilities for coroutines:
44  * [Dispatchers.setMain] to override [Dispatchers.Main] in tests;
45  * [TestCoroutineScope] to test suspending functions and coroutines.
46* [debug](kotlinx-coroutines-debug/README.md) — debug utilities for coroutines:
47  * [DebugProbes] API to probe, keep track of, print and dump active coroutines;
48  * [CoroutinesTimeout] test rule to automatically dump coroutines on test timeout.
49  * Automatic integration with [BlockHound](https://github.com/reactor/BlockHound).
50* [reactive](reactive/README.md) — modules that provide builders and iteration support for various reactive streams libraries:
51  * Reactive Streams ([Publisher.collect], [Publisher.awaitSingle], [kotlinx.coroutines.reactive.publish], etc),
52  * Flow (JDK 9) (the same interface as for Reactive Streams),
53  * RxJava 2.x ([rxFlowable], [rxSingle], etc), and
54  * RxJava 3.x ([rxFlowable], [rxSingle], etc), and
55  * Project Reactor ([flux], [mono], etc).
56* [ui](ui/README.md) — modules that provide coroutine dispatchers for various single-threaded UI libraries:
57  * Android, JavaFX, and Swing.
58* [integration](integration/README.md) — modules that provide integration with various asynchronous callback- and future-based libraries:
59  * JDK8 [CompletionStage.await], Guava [ListenableFuture.await], and Google Play Services [Task.await];
60  * SLF4J MDC integration via [MDCContext].
61
62## Documentation
63
64* Presentations and videos:
65  * [Kotlin Coroutines in Practice](https://www.youtube.com/watch?v=a3agLJQ6vt8) (Roman Elizarov at KotlinConf 2018, [slides](https://www.slideshare.net/elizarov/kotlin-coroutines-in-practice-kotlinconf-2018))
66  * [Deep Dive into Coroutines](https://www.youtube.com/watch?v=YrrUCSi72E8) (Roman Elizarov at KotlinConf 2017, [slides](https://www.slideshare.net/elizarov/deep-dive-into-coroutines-on-jvm-kotlinconf-2017))
67  * [History of Structured Concurrency in Coroutines](https://www.youtube.com/watch?v=Mj5P47F6nJg) (Roman Elizarov at Hydra 2019, [slides](https://speakerdeck.com/elizarov/structured-concurrency))
68* Guides and manuals:
69  * [Guide to kotlinx.coroutines by example](https://kotlinlang.org/docs/coroutines-guide.html) (**read it first**)
70  * [Guide to UI programming with coroutines](ui/coroutines-guide-ui.md)
71  * [Debugging capabilities in kotlinx.coroutines](docs/topics/debugging.md)
72* [Compatibility policy and experimental annotations](docs/topics/compatibility.md)
73* [Change log for kotlinx.coroutines](CHANGES.md)
74* [Coroutines design document (KEEP)](https://github.com/Kotlin/KEEP/blob/master/proposals/coroutines.md)
75* [Full kotlinx.coroutines API reference](https://kotlinlang.org/api/kotlinx.coroutines/)
76
77## Using in your projects
78
79### Maven
80
81Add dependencies (you can also add other modules that you need):
82
83```xml
84<dependency>
85    <groupId>org.jetbrains.kotlinx</groupId>
86    <artifactId>kotlinx-coroutines-core</artifactId>
87    <version>1.6.4</version>
88</dependency>
89```
90
91And make sure that you use the latest Kotlin version:
92
93```xml
94<properties>
95    <kotlin.version>1.6.21</kotlin.version>
96</properties>
97```
98
99### Gradle
100
101Add dependencies (you can also add other modules that you need):
102
103```kotlin
104dependencies {
105    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.4")
106}
107```
108
109And make sure that you use the latest Kotlin version:
110
111```kotlin
112plugins {
113    // For build.gradle.kts (Kotlin DSL)
114    kotlin("jvm") version "1.6.21"
115
116    // For build.gradle (Groovy DSL)
117    id "org.jetbrains.kotlin.jvm" version "1.6.21"
118}
119```
120
121Make sure that you have `mavenCentral()` in the list of repositories:
122
123```kotlin
124repositories {
125    mavenCentral()
126}
127```
128
129### Android
130
131Add [`kotlinx-coroutines-android`](ui/kotlinx-coroutines-android)
132module as a dependency when using `kotlinx.coroutines` on Android:
133
134```kotlin
135implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4")
136```
137
138This gives you access to the Android [Dispatchers.Main]
139coroutine dispatcher and also makes sure that in case of a crashed coroutine with an unhandled exception that
140this exception is logged before crashing the Android application, similarly to the way uncaught exceptions in
141threads are handled by the Android runtime.
142
143#### R8 and ProGuard
144
145R8 and ProGuard rules are bundled into the [`kotlinx-coroutines-android`](ui/kotlinx-coroutines-android) module.
146For more details see ["Optimization" section for Android](ui/kotlinx-coroutines-android/README.md#optimization).
147
148#### Avoiding including the debug infrastructure in the resulting APK
149
150The `kotlinx-coroutines-core` artifact contains a resource file that is not required for the coroutines to operate
151normally and is only used by the debugger. To exclude it at no loss of functionality, add the following snippet to the
152`android` block in your Gradle file for the application subproject:
153
154```kotlin
155packagingOptions {
156    resources.excludes += "DebugProbesKt.bin"
157}
158```
159
160### Multiplatform
161
162Core modules of `kotlinx.coroutines` are also available for
163[Kotlin/JS](https://kotlinlang.org/docs/reference/js-overview.html) and [Kotlin/Native](https://kotlinlang.org/docs/reference/native-overview.html).
164
165In common code that should get compiled for different platforms, you can add a dependency to `kotlinx-coroutines-core` right to the `commonMain` source set:
166
167```kotlin
168commonMain {
169    dependencies {
170        implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.4")
171    }
172}
173```
174
175No more additional dependencies are needed, platform-specific artifacts will be resolved automatically via Gradle metadata available since Gradle 5.3.
176
177Platform-specific dependencies are recommended to be used only for non-multiplatform projects that are compiled only for target platform.
178
179#### JS
180
181Kotlin/JS version of `kotlinx.coroutines` is published as
182[`kotlinx-coroutines-core-js`](https://search.maven.org/artifact/org.jetbrains.kotlinx/kotlinx-coroutines-core-js/1.6.4/jar)
183(follow the link to get the dependency declaration snippet) and as [`kotlinx-coroutines-core`](https://www.npmjs.com/package/kotlinx-coroutines-core) NPM package.
184
185#### Native
186
187Kotlin/Native version of `kotlinx.coroutines` is published as
188[`kotlinx-coroutines-core-$platform`](https://mvnrepository.com/search?q=kotlinx-coroutines-core-) where `$platform` is
189the target Kotlin/Native platform. [List of currently supported targets](https://github.com/Kotlin/kotlinx.coroutines/blob/master/gradle/compile-native-multiplatform.gradle#L16).
190
191## Building and Contributing
192
193See [Contributing Guidelines](CONTRIBUTING.md).
194
195<!--- MODULE kotlinx-coroutines-core -->
196<!--- INDEX kotlinx.coroutines -->
197
198[launch]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/launch.html
199[async]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/async.html
200[Job]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-job/index.html
201[Deferred]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-deferred/index.html
202[Dispatchers]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-dispatchers/index.html
203[Dispatchers.Main]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-dispatchers/-main.html
204[Dispatchers.Default]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-dispatchers/-default.html
205[delay]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/delay.html
206[yield]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/yield.html
207[_coroutineScope]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/coroutine-scope.html
208[_supervisorScope]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/supervisor-scope.html
209[withContext]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/with-context.html
210[withTimeout]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/with-timeout.html
211[MainScope()]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-main-scope.html
212[SupervisorJob()]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-supervisor-job.html
213[CoroutineExceptionHandler]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-coroutine-exception-handler/index.html
214[Dispatchers.IO]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-dispatchers/-i-o.html
215[asCoroutineDispatcher]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/as-coroutine-dispatcher.html
216[Promise.await]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/await.html
217[promise]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/promise.html
218[Window.asCoroutineDispatcher]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/as-coroutine-dispatcher.html
219
220<!--- INDEX kotlinx.coroutines.flow -->
221
222[Flow]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/-flow/index.html
223[_flow]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/flow.html
224[filter]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/filter.html
225[map]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/map.html
226
227<!--- INDEX kotlinx.coroutines.channels -->
228
229[Channel]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.channels/-channel/index.html
230
231<!--- INDEX kotlinx.coroutines.selects -->
232
233[select]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.selects/select.html
234
235<!--- INDEX kotlinx.coroutines.sync -->
236
237[Mutex]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.sync/-mutex/index.html
238[Semaphore]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.sync/-semaphore/index.html
239
240<!--- MODULE kotlinx-coroutines-test -->
241<!--- INDEX kotlinx.coroutines.test -->
242
243[Dispatchers.setMain]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-test/kotlinx.coroutines.test/set-main.html
244[TestCoroutineScope]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-test/kotlinx.coroutines.test/-test-coroutine-scope/index.html
245
246<!--- MODULE kotlinx-coroutines-debug -->
247<!--- INDEX kotlinx.coroutines.debug -->
248
249[DebugProbes]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-debug/kotlinx.coroutines.debug/-debug-probes/index.html
250
251<!--- INDEX kotlinx.coroutines.debug.junit4 -->
252
253[CoroutinesTimeout]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-debug/kotlinx.coroutines.debug.junit4/-coroutines-timeout/index.html
254
255<!--- MODULE kotlinx-coroutines-slf4j -->
256<!--- INDEX kotlinx.coroutines.slf4j -->
257
258[MDCContext]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-slf4j/kotlinx.coroutines.slf4j/-m-d-c-context/index.html
259
260<!--- MODULE kotlinx-coroutines-jdk8 -->
261<!--- INDEX kotlinx.coroutines.future -->
262
263[CompletionStage.await]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-jdk8/kotlinx.coroutines.future/await.html
264
265<!--- MODULE kotlinx-coroutines-guava -->
266<!--- INDEX kotlinx.coroutines.guava -->
267
268[ListenableFuture.await]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-guava/kotlinx.coroutines.guava/await.html
269
270<!--- MODULE kotlinx-coroutines-play-services -->
271<!--- INDEX kotlinx.coroutines.tasks -->
272
273[Task.await]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-play-services/kotlinx.coroutines.tasks/await.html
274
275<!--- MODULE kotlinx-coroutines-reactive -->
276<!--- INDEX kotlinx.coroutines.reactive -->
277
278[Publisher.collect]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-reactive/kotlinx.coroutines.reactive/collect.html
279[Publisher.awaitSingle]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-reactive/kotlinx.coroutines.reactive/await-single.html
280[kotlinx.coroutines.reactive.publish]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-reactive/kotlinx.coroutines.reactive/publish.html
281
282<!--- MODULE kotlinx-coroutines-rx2 -->
283<!--- INDEX kotlinx.coroutines.rx2 -->
284
285[rxFlowable]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-rx2/kotlinx.coroutines.rx2/rx-flowable.html
286[rxSingle]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-rx2/kotlinx.coroutines.rx2/rx-single.html
287
288<!--- MODULE kotlinx-coroutines-rx2 -->
289<!--- INDEX kotlinx.coroutines.rx2 -->
290<!--- MODULE kotlinx-coroutines-reactor -->
291<!--- INDEX kotlinx.coroutines.reactor -->
292
293[flux]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-reactor/kotlinx.coroutines.reactor/flux.html
294[mono]: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-reactor/kotlinx.coroutines.reactor/mono.html
295
296<!--- END -->
297