Maven compile error

[<michalk AT awpi.com>]

I am trying to build gs-core 2.1.0-SNAPSHOT with maven 3.6.3, java 11.0.16, 
and
am getting an error:

[INFO] 
------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] 
------------------------------------------------------------------------
[INFO] Total time:  5.588 s
[INFO] Finished at: 2022-07-29T13:42:44-05:00
[INFO] 
------------------------------------------------------------------------
[ERROR] Failed to execute goal org.jacoco:jacoco-maven-plugin:0.8.5:report
(default-report) on project gs-core: Execution default-report of goal
org.jacoco:jacoco-maven-plugin:0.8.5:report failed: A required class was
missing while executing org.jacoco:jacoco-maven-plugin:0.8.5:report:
org/codehaus/plexus/util/xml/XmlStreamReader
[ERROR] -----------------------------------------------------

Can anyone else validate this problem?  I can't upgrade Maven at this time due
to apt package dependency problems on my machine.

I want to make org.graphstream.stream.SourceBase.manageEvents() syncronized.  
I
think the non-atomic operation with the boolean test is causing problems.