What's new in JDK 9(my short version)

1.Java platform module system
- optional phase, link time, between compile and run time.
- options to javac, jlink and java where you can specify module paths
- modular JAR file, which is a JAR with module-info.class in root dir
- JMOD format, which can include native code compared to JAR
- JDK divided into modules, thus enabling combination of modules.
- new URI scheme for naming modules, classes and resources stored in a runtime image without revealing the internal structure or format of the image.
- Removes rt.jar and tools.jar from the Java runtime.
- Makes most JDK internal APIs inaccessible by default, with some widely used exceptions.

2.New version-string scheme. $MAJOR.$MINOR.$SECURITY.$PATCH
- A major release contains new features and changes to existing features, which are planned and announced well in advance - A minor version number that is incremented for each minor update, such as bug fixes, revisions to standard APIs or implementation of features outside the scope of the relevant platform specifications
- Security is the version number that is incremented for a security-update release, which contains critical fixes, including those necessary to improve security. PATCH is the version number that is incremented for a release containing security and high-priority customer fixes that have been tested together

3.Language features
- @SafeVargs annotation
- effectively final variables to be used in try with resources
- support for private interface methods.

4.JVM
- G1 improvements.
- common logging system.
- G1 made Default.
- Concurrent Mark Sweep is deprecated.

5.Core
- Improvements on the OS Processes API
- Changed internal representation of strings from char array with 2 bytes for each character to a byte array plus encoding flag field.
- Minimal logging API that can be defined by apps to route logging to library of choice, or default to java.util.logging is used.
- Easier to make collections of small number of elements, like Set.of("","","")
- @Deprecated interface gets new parameters, like since and forRemoval.
- New API that can be used to hind that a spin loop is executing, this info being available for futher use for performance improvements.
- Stack walking API. Easy access to the information in stack traces.
- Support for 2.11.0 Xerces parser.

6.Nashorn
- Allows apps to parse and analyze ECMAScript code, parsing returns Abstract Syntax Tree.
- Implements features introduced in ECMAScript 6, like:
   a)template strings
   b)let, const and block scope
   c)iterators and for..of loops
   d)Map, Set, WeakMap, WeakSet
   e)Symbols
   f)Binary and Octal literals

7.Client Technologies
- Supports in AWT for multi resolution images, in order to adapt to different devices.
- public APIs for JavaFx UI controls and CSS that were previously available only through internal packages.
- @beaninfo replaced with JavaBean, BeanProperty, SwingContainer
- Add TIFF as standard to javax.imageio
- Automatic scale and size of AWT and Swing components to HiDPI on Windows and Linux.
Prior, apps were sized and rendered based on pixels, which led to components too small to read or use.
- New methods to java.awt.Desktop

8.Internationalization
- Support for Unicode 8.0. JDK 8 supported 6.2. 10555 more chars, 29 scripts and 42 blocks.
- Use of Common Locale Data Repository XML based locale data, which was added in JDK 8, as default. Previously, JRE was used.
- Loads properties files in UTF-8. Previously ISO-8859-1 was used. UTF-8 is better at representing non-Latin characters.