Caché Monitor have no support for Java 9 and later cause of some very fundamental code breaking changes in this java runtime versions.
Please notice the End of Public Updates for Oracle JDK 7
As outlined in the Oracle JDK Support Roadmap, after April 2015, Oracle will not post further updates of Java SE 7 to its public download sites. Customers who need continued access to critical bug fixes and security fixes as well as general maintenance for Java SE 7 or older versions can get long term support through Oracle Java SE Support. The process of migrating users from Java 7 to Java 8 through the auto update feature is expected to take place after the January 2015 CPU release.
Java 8 is not supported with Caché Monitor 2.54 and earlier. For these releases, we recommend using the latest release of Java 7.