The file "gradlewj.bat" defines the path to a JDK.
It may be used, when another java, than defined via JAVA_HOME is needed for the project.
Modify that file, so that the path in it points to your JDK.
Use it, as if you would use gradlew.
gradlewj <GRADLEW COMMANDS>
To package the project as a jar type:
gradlew build
The output will be under .\out
To run the project as a java applicaiton type
gradlew run
The application will be started.