Coroutine

Setup from commandline

Refer to https://stackoverflow.com/questions/79103733/how-to-use-kotlinx-with-the-command-line-compiler-kotlinc

Visit https://mvnrepository.com/artifact/org.jetbrains.kotlinx/kotlinx-coroutines-core-jvm, select a version, e.g., 1.10.1, and it goes to https://mvnrepository.com/artifact/org.jetbrains.kotlinx/kotlinx-coroutines-core-jvm/1.10.1. Click the link https://repo1.maven.org/maven2/org/jetbrains/kotlinx/kotlinx-coroutines-core-jvm/1.10.1/kotlinx-coroutines-core-jvm-1.10.1.jar.

Hint

For android, it is kotlinx-coroutines-android. For js, it is kotlinx-coroutines-core-js.

./code/coroutine/Hello.kt

import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking

fun main() =
  runBlocking {
    launch {
      delay(1000)
      println("Kotlin Coroutines World!")
  }
  println("Hello")
}

Run:

kotlinc -cp ./kotlinx-coroutines-core-jvm-1.10.1.jar Hello.kt -d hello.jar

It gives the following error:

kotlinx-coroutines-core-jvm-1.10.1.jar!/META-INF/kotlinx-coroutines-core.kotlin_module:
error: module was compiled with an incompatible version of Kotlin.
The binary version of its metadata is 2.1.0, expected version is 1.8.0.

kotlinc --version prints:

info: kotlinc-jvm 1.8.0 (JRE 17.0.5+9-LTS-191)

so we need to update our kotlin:

cd $HOME/software/
mkdir -p kotlin
cd kotlin
wget https://github.com/JetBrains/kotlin/releases/download/v2.1.0/kotlin-compiler-2.1.0.zip
unzip kotlin-compiler-2.1.0.zip

mv kotlinc 2.1.0
export PATH=$HOME/software/kotlin/2.1.0/bin:$PATH

Then we can run:

kotlinc -cp ./kotlinx-coroutines-core-jvm-1.10.1.jar Hello.kt -d hello.jar

It will generate a file hello.jar.

ls -lh hello.jar
-rw-r--r--  1 fangjun  staff   4.0K Jan  1 16:20 hello.jar

We can run it with:

kotlin -classpath ./hello.jar:./kotlinx-coroutines-core-jvm-1.10.1.jar  HelloKt

Alternatively, we can use:

kotlinc -cp ./kotlinx-coroutines-core-jvm-1.10.1.jar Hello.kt -include-runtime -d hello.jar

hello.jar is much larger than before:

ls -lh hello.jar
-rw-r--r--  1 fangjun  staff   4.6M Jan  1 16:22 hello.jar

Then we can use:

java -classpath ./hello.jar:./kotlinx-coroutines-core-jvm-1.10.1.jar  HelloKt
java -cp ./hello.jar:./kotlinx-coroutines-core-jvm-1.10.1.jar  HelloKt
kotlin -cp ./hello.jar:./kotlinx-coroutines-core-jvm-1.10.1.jar  HelloKt
kotlin -classpath ./hello.jar:./kotlinx-coroutines-core-jvm-1.10.1.jar  HelloKt

thread related functions

Thread.sleep(1000L) # sleep 1000ms, i.e., 1s

common suspendable functions

delay(1000L) # sleep 1000m, i.e., 1s

Predefined coroutine dispatcher

• Dispatchers.Default: Compute-intensive

• Dispatchers.IO: File I/O, blocking socket I/O, etc

• Dispatchers.Main: For UI thread

functions without a scope

• runBlocking, it is not a suspend function, coroutine builder, scope builder

• coroutineScope(), it is a suspend function, scope builder

• withContext(), it is a suspend function

functions requiring a scope

• launch(), e.g., GlobalScope.lanuch, it is not a suspend function. coroutine builder

• async(), e.g., GlobalScope.async, it is not a suspend function. coroutine builder