55 New Features in JDK 9

© Copyright Azul Systems 2017
@speakjava
55 New Features
In JDK 9
Simon Ritter
Deputy CTO, Azul Systems
1

Major Features

Modularity/Jigsaw
 Standard class libraries modularised (JEP 220)
– rt.jar now 85 modules
 Most internal APIs now encapsulated (JEP 260)
– Some can be used with command line option
– sun.misc.Unsafe
 Modular source code (JEP 201)
– JDK source code re-organised to support modules
– Not the module system
3

jlink: The Java Linker (JEP 282)
4
Modular run-time
image
…confbin
jlink
$ jlink --modulepath $JDKMODS
--addmods java.base –output myimage
$ myimage/bin/java –listmods
java.base@9.0

jlink: The Java Linker (JEP 282)
$ jlink --modulepath $JDKMODS:$MYMODS
--addmods com.azul.app –output myimage
$ myimage/bin/java –listmods
java.base@9.0
java.logging@9.0
java.sql@9.0
java.xml@9.0
com.azul.app@1.0
com.azul.zoop@1.0
com.azul.zeta@1.0
Version numbering for
information purposes only
“It is not a goal of the module
system to solve the version-
selection problem”

Factory Methods For Collections (JEP 269)
 Static factory methods on List, Set and Map interfaces
– Create compact, immutable instances
– 0 to 10 element overloaded versions
6
Set<String> set = new HashSet<>();
set.add("a");
set.add("b");
set.add("c");
set = Collections.unmodifiableSet(set);
Set<String> set = Set.of("a", "b", "c");

Stream Enhancements
 dropWhile()/takeWhile()
– Like skip/limit but uses Predicate rather than number
 Improved iterate
– Enables a stream to be more like a for loop
 Parallel Files.lines()
– Memory mapped, divided on line break boundary
 Stream from Optional
– Stream of zero or one elements
7

Multi-Release Jar Files (JEP 238)
 Multiple Java release-specific class files in a single archive
 Enhance jar tool to create multi-release files
 Support multi-release jar files in the JRE
– Classloaders
– JarFile API
 Enhance other tools
– javac, javap, jdeps, etc.
 Also, modular jar files
8

REPL: jshell (JEP 222)
 Read-Eval-Print Loop
– Simple prototyping
9

Concurrency Updates (JEP 266)
 Reactive streams publish-subscribe framework
 Asynchronous, non-blocking
 Flow
– Publisher, Subscriber, Processor, Subscription
 SubmissionPublisher utility class
– Asynchronously issues items to current subscribers
– Implements Flow.Processor
10

Concurrency Updates (JEP 266)
 CompletableFuture additions
– Delays and timeouts
– Better support for sub-classing
– New utility methods
 minimalCompletionStage
 failedStage
 newIncompleteFuture
 failedFuture
11

Enhanced Deprecation (JEP 277)
 We have @deprecated and @Deprecated
– Used to cover too many situations
 New methods in Deprecated annotation
– boolean forRemoval()
 Will this ever be removed?
– String since()
 JDK Version when this was deprecated
 Several @Deprecated tags added
– java.awt.Component.{show(),hide()} removed
12

Milling Project Coin (JEP 213)
 Underscore no longer valid as identifier
– Ready for use in Lambdas
 Private methods in interfaces
– Multiple inheritance of behaviour makes this logical
 Effectively final variables in try-with-resources
– Variables from outside try block
 Allow @SafeVarargs on private instance methods
– In addition to constructors, final and static methods
 Diamond operator with anonymous classes
– Extending type inference further
13

Standards

Updating To Relevant Standards
 Unicode 7.0/8.0 (JEP 227/267)
– 7.0: 2,834 new characters
– 8.0: 7,716 new characters
 PKCS12 key stores by default (JEP 229)
– Move from JKS to PKCS12
 HTML5 javadocs (JEP 224)
– Flashier documentation
 SHA 3 hash algorithms (JEP 287)
– Keeping ahead of the hackers
15
}seriously!

Smaller Features
 UTF-8 property files (JEP 226)
– ResourceBundle API updated to load these files
 DRBG-Based SecureRandom implementations (JEP 273)
– Deterministic Random Bit Generator
 XML Catalog API (JEP 268)
– Supports OASIS XML catalog API v1.1
– For use with JAXP
16

Inside The JVM

Default Collector: G1 (JEP 248)
 G1 now mature in development
 Designed as low-pause collector
 Concurrent class unloading (JEP 156) JDK8u40
– Useful enhancement to improve G1
 Still falls back to full compacting collection
– Pause times proportional to heap size
– Use Zing from Azul for truly pauseless
18

Better String Performance
 Compact strings (JEP 254)
– Improve the space efficiency of the String class
– Not using alternative encodings
 Store interned strings in CDS archive (JEP 250)
– Share String and char[] objects between JVMs
 Indify String concatenation (JEP 280)
– Change from static String-concatenation bytecode
sequence to invokedynamic
– Allow future performance improvements
19

Marlin Graphics Renderer (JEP 265)
 Replaces Pisces open-source renderer
– Comparable performance to closed-source Ductus
20

Smaller Features
 Improve contended locking (JEP 143)
– Field reordering/cache line alignment
 Leverage CPU instructions for GHASH and RSA (JEP 246)
– 34-150x better performance (for certain tests)
 Update JavaFX to newer version of GStreamer (JEP 257)
– Media class
– Better security, stability and performance
21

Smaller Features
 Segmented Code Cache (JEP 197)
– Separate non-method, profiled and non-profiled code
 Unified JVM logging (JEP 158)
– Common logging system for all components of JVM
 Unified GC logging (JEP 271)
– Re-implement GC logging using unified JVM logging
22

Specialised

Spin-Wait Hints (JEP 285)
 Proposed by Azul
– We rock!
 A new method for Thread class
– onSpinWait()
 Enables the x86 PAUSE instruction to be used from Java
code
– If available
– Ignored otherwise
– Improved performance for things like Disruptor
24

Variable Handles (JEP 193)
 Replacement for parts of sun.misc.Unsafe
 Fence operations
– Fine grained memory control
– Atomic operations on object fields and array elements
 VarHandle
– compareAndExchange(), compareAndSet()
– getAndAdd(), getAndSet()
– acquireFence(), releaseFence()
25

Enhanced Method Handles (JEP 274)
 Support for
– loops
– try/finally blocks
 Better argument handling
– Spreading
– Collection
– Folding
 More lookup functions
– Non-abstract methods in interfaces, classes
26

Smaller Features
 Compiler control (JEP 165)
– Control of C1/C2 JIT, not javac
– Directive file
– Runtime changes via jcmd
 Process API updates (JEP 102)
– Native process (Process/ProcessHandle)
– More information: pid, arguments, start time, CPU usage,
name
– Control subject to security manager permissions
27

Housekeeping

New Version String Format (JEP 223)
 Old
– Limited update release/Critical patch update (CPU)
– JDK 8u121 or jdk1.8.0_u121
– Which has more patches, JDK 7u55 or JDK 7u60?
 New
– JDK $MAJOR.$MINOR.$SECURITY.$PATCH
– Easy to understand by humans and apps
– Semantic versioning
29

JDK/JRE File Structure (JEP 220)
30
bin
Pre-JDK 9 JDK 9
lib
tools.jar
jre
bin
rt.jar
lib
libconfbin
jre directory
tools.jar
rt.jar

Smaller Features
 Searchable API documentation (JEP 225)
– Finally! Java API docs enter the 21st century
 Annotations pipeline 2.0 (JEP 217)
– Repeating, type and Lambda annotations in JDK 8
– Redesign of javac annotation pipeline
 Parser API for Nashorn (JEP 236)
– API for Nashorn abstract tree syntax
31

General Clean Up
 Disable SHA-1 certificates (JEP 288)
– Mostly
 In some situations SHA-1 certs. will still be accepted
 Deprecate the Applet API (JEP 289)
– Not many people still use this
32

Removed From JDK 9
 Six deprecated APIs (JEP 162)
– ActionListeners in Pack200 and LogManager
 JRE version selection command line option (JEP 231)
– -version: no longer accepted
 Demos and samples (JEP 298)
– Out-of-date, unmaintained
33

Removed From JDK 9
 JVM TI hprof agent (JEP 240)
– Only ever intended as a demo of JVM TI
– Useful features now in other tools (like jmap)
 Remove the jhat tool (JEP 241)
– Experimental tool added in JDK 6
– Unsupported
– Better heap visualisation tools available
34

Removed GC Options (JEP 214)
 Deprecated in JDK 8 (JEP 173)
35
DefNew + CMS : -XX:-UseParNewGC -XX:+UseConcMarkSweepGC
ParNew + SerialOld : -XX:+UseParNewGC
ParNew + iCMS : -Xincgc
ParNew + iCMS : -XX:+CMSIncrementalMode -XX:+UseConcMarkSweepGC
DefNew + iCMS : -XX:+CMSIncrementalMode -XX:+UseConcMarkSweepGC
-XX:-UseParNewGC
CMS foreground : -XX:+UseCMSCompactAtFullCollection
CMS foreground : -XX:+CMSFullGCsBeforeCompaction
CMS foreground : -XX:+UseCMSCollectionPassing

Incubator Modules (JEP 11)
 Develop APIs without making them part of the standard
– At least not straight away
 Allow developers to “kick the tyres”
– Not always possible to get a new API right first time
 Move from incubator to full module
– Becomes part of the standard
 JDK 9 only has one incubator: HTTP/2 (JEP 110)
 Some concerns about fragmentation
--do-not-resolve-by-default
36

Summary

JDK 9
 Big new feature is modularity
– Covers numerous different areas
– Modules, jink, jmods, etc.
 Smaller developer features
– New APIs for streams
– Reactive API
– REPL/jshell
 Many smaller performance/standards features
 Time to start testing, if you’re not already
38

Zulu Java
 Azul’s binary distribution of OpenJDK
– Passes all TCK tests
– Multi-platform (Windows, Linux, Mac)
– FREE!
 Happy to sell you support, including older versions
 JDK 6, 7, 8 and 9 (Early Access)
39
www.zulu.org/download

@speakjava
Questions
Simon Ritter
Deputy CTO, Azul Systems
40

55 New Features in JDK 9

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