'Unrecognized VM option 'UseConcMarkSweepGC' when running sample project

I have followed the instructions for getting started with codenameone in IntelliJ, yet when I set up my first project, based on the sample app I get this error:

"C:\Program Files\Java\jdk-15.0.1\bin\java.exe" -Xms128m -Xmx1014m -XX:ReservedCodeCacheSize=512m -XX:+UseConcMarkSweepGC -XX:SoftRefLRUPolicyMSPerMB=50 -XX:CICompilerCount=2 -XX:+HeapDumpOnOutOfMemoryError -XX:-OmitStackTraceInFastThrow -ea -Dsun.io.useCanonCaches=false -Djdk.http.auth.tunneling.disabledSchemes=\"\" -Djdk.attach.allowAttachSelf=true -Djdk.module.illegalAccess.silent=true -Dkotlinx.coroutines.debug=off "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2020.3.1\lib\idea_rt.jar=61544:C:\Program Files\JetBrains\IntelliJ IDEA 2020.3.1\bin" -Dfile.encoding=UTF-8 -classpath "C:\Users\reinp\OneDrive - beuthhs\beuth\Patterns und Frameworks\justtrivia\out\production\justtrivia;C:\Users\reinp\OneDrive - beuthhs\beuth\Patterns und Frameworks\justtrivia\src;C:\Users\reinp\OneDrive - beuthhs\beuth\Patterns und Frameworks\justtrivia\lib\CodenameOne.jar;C:\Users\reinp\OneDrive - beuthhs\beuth\Patterns und Frameworks\justtrivia\JavaSE.jar;native\internal_tmp;lib\impl\cls" com.codename1.impl.javase.Simulator com.patrickreinbold.justtrivia.JustTrivia
Unrecognized VM option 'UseConcMarkSweepGC'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

Process finished with exit code 1

I saw that this has to do with Java 8 but in the IntelliJ instructions it says nothing about using Java 8. Is Java 8 always necessary or can codenameone run with Java 15, too?

EDIT: I have now got it to open by simply copying the first line with the java command and removing the UseConcMarkSweepGC flag, then running it in terminal. But I am still not sure if that is "the correct way" to do it or if something could break along the way now.

javaintellij-ideacodenameone


Solution 1:[1]

This is a problem with the netbeans build script but this isn't really relevant as Codename One only supports Java 8 and Java 11 (at this time) so you should use one of those versions at the moment.

Solution 2:[2]

Try ignore unsupported VM options: -XX:+IgnoreUnrecognizedVMOptions

Solution 3:[3]

run export JAVA_HOME=$(/usr/libexec/java_home -v 1.8)

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Shai Almog
Solution 2 Mikhail U
Solution 3 Vinayak Gupta

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