technosynoptic

More Module System, e.g. self-describing collection of code and data
- Using jlink, to introduce a new optional phase, link time, which is in-between compile time and run time, during which a set of modules can be assembled and optimized into a custom runtime image
- The modular JAR file with module-info.class file in its root directory.
- Using jmod tool, the New JMOD format can be created. (new packaging format similar to JAR)
New version schema ($MAJOR.$MINOR.$SECURITY.$PATCH)
java shell: jshell
Compile for old java version (6 – java6)
```
javac -source 6 -target 6 HelloWorld.java
```
More Diagnostic Commands: jcmd (jcmd pid help command)
Multi-Release JAR Files: Extends the JAR file format to enable multiple, Java release-specific versions of class files to coexist in a single archive
Removes the hprof, jhat from the JDK
More Security: DTLS, TLS, disable X.509 certificate chains with SHA-1-based signatures, PKCS12 keystores by default, SHA-3 cryptographic hash functions
The Garbage-First Garbage Collector (G1 GC) is the default garbage collector in JDK 9.
JavaDB, which was a rebranding of Apache Derby, isn’t included in JDK 9.
The launchers java-rmi.exe from Windows and java-rmi.cgi from Linux and Solaris have been removed.
In JDK 9, the Windows 32–bit client VM is not available. Only a server VM is offered.
Java VisualVM isn’t bundled with JDK 9.
The AppleScript engine is removed in JDK 9.

The Java 9 installer creates these Windows registry keys when installing the JRE:

The Java 8u152 installer creates these Windows registry keys when installing the JRE:

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