Beginning in macOS 10.14.5, software signed with a new Developer ID certificate and all new or updated kernel extensions must be notarized to run. Beginning in macOS 10.15 (Catalina), all software built after June 1, 2019, and distributed with Developer ID must be notarized. However, you aren’t required to notarize software that you distribute through the Mac App Store because the App Store submission process already includes equivalent security checks.

https://help.apple.com/xcode/mac/current/#/dev033e997ca

When running an app that is NOT notarized you will get this error:

xxx can’t be opened because Apple cannot check it for malicious software

To open it, user need to go to System Preferences > Security & Privacy > General tab and click “Open Anyway…”. (or right click the app to open?)

According to Oracle, Java 14 is the first release that complies with the new macOS 10.15 hardening and notarization requirements.

https://www.oracle.com/technetwork/java/javase/using-jdk-jre-macos-catalina-5781620.html

AdoptOpenJDK is working on getting OpenJDK8 notarizable. Currently the latest version 8u252 is not notarized however 8u252.1 will be.

https://blog.adoptopenjdk.net/2020/04/adoptopenjdk-8u252-1107-and-1401-available/

https://blog.adoptopenjdk.net/2020/05/a-simple-guide-to-notarizing-your-java-application/