Java 9 sneak peek

Who am I
Software consultant (CoffeeCupConsulting)
BG JUG board member (http://jug.bg)
OpenJDK and Oracle RBDMS enthusiast
Twitter: @martin_fmi

Agenda
• Java 9: module system
• Networking break
• Java 9: the good parts

Goals
• Break the monolith JDK into smaller modules
• Provide module system for Java applications
java.base
java.logging
java.xml
java.sql

Supporting work …
• JDK 8 compact profiles
javac -profile <profile_name>
compact 1 compact 2 compact 3

Module metadata
• Provided by module-info.java
• Extends the syntax of the Java language
• Exposed at runtime via the java.lang.Module class

Module metadata
module application.demo {
requires java.logging;
requires banking.server;
provides
bg.jug.banking.server.applications.BankingApplication
with bg.jug.banking.app.demo.DemoApplication;
}
Module module = object.getClass().getModule();

Sneak peek
• Java Shell (JShell)
• New process API
• Small language enhancements
• G1 as the default garbage collector

Sneak peek
• New HTTP/2 client
• New stack walking API
• New reactive programming API
• Misc

Java Shell (JShell)
• Provides a read-eval-print-loop (REPL) shell for the
Java platform
• Provides a playground for the Java language and its
supporting APIs
• Provided by the jshell tool part of the JDK installation

New process API
• Before Java 9 ….
Process p = Runtime.getRuntime().exec("cmd /c notepad");
ProcessBuilder pb = new ProcessBuilder("cmd", "/c", “notepad");
Process p = pb.start();

New process API
• Limited support for process handling up to JDK 9
• Mostly for creation of a process …

New process API
• java.lang.Process extended with new methods
• New Java.lang.ProcessHandle class for process
management in a streamlike manner
onExit()
supportsNormalTermination()
toHandle()
children()
descendants()
pid()
info()

Small language enhancements
• Not really many … (var definitions did not make it
in Java 9)
• A few very minor enhancements part of project
Coin (the most significant being private methods
in interfaces)

G1 GC
• Replaces parallel GC as the default GC
• A low-pause collector
• Sacrifyes higher throughput
(… targets to provide better experience for users)

G1 GC
• The unit of work is a heap region in a generation
• Provides new framework for further optimizations
• Most other GCs work on generations directly

G1 GC
• Targets to clear as much garbage as possible
• Has larger footprint than parallel GC

HTTP/2 client
• Still in incubation (although part of release)
• Provides support for HTTP 2.0

Stack walking API
• new API for easier manipulation of stack traces
• Provided by the java.lang.Stackwalker class

Reactive programming API
• New publish-subscribe API
• Provided by the java.util.concurrent.Flow interface

Misc
• New collection factory methods
Set.of(…)
Map.of(…)
Map.ofEntries(…)
List.of(…)

Misc
• Multirelease JAR files
• Compact strings
• Variable handles

Misc
• A number of TLS enhancements
• Javadoc enhancements
• A number of others …

Summary
• The new module system is beyond doubt the
most significant feature of JDK 9
• There are many new APIs in JDK 9 that extend
the developer’s toolbox

References
New features in Java 9
https://docs.oracle.com/javase/9/whatsnew/
Project Jigsaw
http://openjdk.java.net/projects/jigsaw/
Oracle JDK 9 Documentation Early Access
https://docs.oracle.com/javase/9/javase-docs.htm

References
JShell tutorial
http://cr.openjdk.java.net/~rfield/tutorial/JShellTut
orial.html
Java 9 Process API: The Shape of Things to Come
http://iteratrlearning.com/java/2017/03/12/java9-
process-api.html

References
Process API – Java 9
https://blog.oio.de/2016/09/02/process-api-java-9/
JDK 9 early access download
http://jdk.java.net/9/
Java 9: The (G1) GC Awakens
https://www.slideshare.net/MonicaBeckwith/java-9-the-
g1-gc-awakens

Java 9 sneak peek

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