I have installed the OpenJDK11+OpenJFX11 from the suggested link in the B4J and B4A product page.
I unzipped it, I updated my paths in B4J and compiled successfully an Application. I exited B4J and tried to run the jar by double clicking on it but I see a black command prompt windows which closes and nothing runs.
C:\Users\Nikos>java -version
Error: opening registry key 'Software\JavaSoft\Java Runtime Environment'
Error: could not find java.dll
Error: Could not find Java SE Runtime Environment.
C:\Users\Nikos>java
Error: opening registry key 'Software\JavaSoft\Java Runtime Environment'
Error: could not find java.dll
Error: Could not find Java SE Runtime Environment.
C:\Users\Nikos>java -jar c:\B4X\Tools\JsonTree.jar
Error: opening registry key 'Software\JavaSoft\Java Runtime Environment'
Error: could not find java.dll
Error: Could not find Java SE Runtime Environment.
C:\Users\Nikos>cd\B4X\Java\Jdk-11.0.1\bin
C:\B4X\Java\jdk-11.0.1\bin>java -jar c:\B4X\Tools\JsonTree.jar
Error: JavaFX runtime components are missing, and are required to run this application