shebang script:

$ cat Hello
#!/usr/bin/env java --enable-preview

void main() {
   println("hello");
}

$ chmod 755 Hello

$ ./Hello
Error: Could not find or load main class ..Hello
Caused by: java.lang.ClassNotFoundException: //Hello

Per JEP 330

"The --source option must also be used to specify the source version of the source code when the --enable-preview option is used."

But, the error message above is misleading. The error message may mention about --source option requirement.