This is a well known limitation of our Java analyzer. It is using the IDE runtime JRE to resolve JDK classes, while in a perfect world it should be using the JRE configured to compile the project.
See: https://jira.sonarsource.com/browse/SONARJAVA-3056
For now your only option is to upgrade SonarJava to a more recent version, and it might indeed require to also upgrade your server. Or stop using connected mode…