Exit code: 1 - javadoc: error - The code being documented uses packages in the unnamed module, but the packages defined in https://docs.oracle.com/en/java/javase/11/
I was facing the same issue. I was using Java 11.0.3 and org.apache.maven.plugins:maven-javadoc-plugin:2.10.4:jar. Updating the maven-javadoc-plugin version to 3.2.0 worked perfectly for me.