ExtraPropDefns the class which handles "extra property definitions" for @requires clauses uses the following patterns to extract the class name java source:

    private static Pattern packagePattern =
            Pattern.compile("package\\s+(((?:\\w+\\.)*)(?:\\w+))\\s*;");
    private static Pattern classPattern =
            Pattern.compile("(?:public\\s+)?(?:class|enum|interface)\\s+(\\w+)");

When I defined my class as:
/**
 * The class to be invoked by jtreg prior Test Suite execution to
 * collect information about VM.
 */
public class VMProps implements Callable<Map<String, String>> {
   ...
}

jtreg reported a very confusing message:

java.lang.ClassNotFoundException: requires.to
Error: failed to get JDK properties for /set/java/re/jdk/9/promoted/latest/binaries/solaris-x64/bin/java ; exit code 1