JDK 9 supports a new environment variable `JDK_JAVA_OPTIONS` to prepend options to those specified on the command line. The new environment variable has several advantages over the legacy/unsupported `_JAVA_OPTIONS` environment variable including the ability to include `java` launcher options and `@file` support. The new environment variable may also be useful when migrating from JDK 8 to JDK 9 for cases where new command line options (that are not supported by JDK 8) are needed.

For more details, see [java launcher reference guide](http://docs.oracle.com/javase/9/tools/java.htm#JSWOR-GUID-3B1CE181-CD30-4178-9602-230B800D4FAE).