Environment:

~~~

$ java -version
openjdk version "17.0.9" 2023-10-17
OpenJDK Runtime Environment (Red_Hat-17.0.9.0.9-4) (build 17.0.9+9)
OpenJDK 64-Bit Server VM (Red_Hat-17.0.9.0.9-4) (build 17.0.9+9, mixed mode, sharing)

~~~

Downloading the Resteasy application

https://code.quarkus.redhat.com/?e=resteasy-reactive

and trying to compile the code 

Results in following Build Failure

~~~

INFO] Compiling 1 source file with javac [debug release 21] to target/classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  04:11 min
[INFO] Finished at: 2024-05-27T14:55:34+10:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.12.1:compile (default-compile) on project code-with-quarkus: Fatal error compiling: error: release version 21 not supported -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

~~~

Has to  be manually corrected from 21 to 17, in pom.xml

e.g

~~~

 <maven.compiler.release>17</maven.compiler.release>

~~~