Java 9 is a major feature release. The following summarizes features and enhancements in Java language version 9.
- Allow @SafeVargs annotation on private instance methods
- Allow final variables to be used as resources in the try-with-resources statement
- Allow the use of diamond with anonymous classes if the type of the inferred type is denotable.
- Complete the removal of underscore from the set of legal identifier names. This was started in java version 8.
- Add support for private interface methods.
Reference : https://docs.oracle.com/javase/9/language/toc.htm#JSLAN-GUID-16A5183A-DC0D-4A96-B9D8-AAC9671222DD