Jdk 10 sneak peek

@martin_fmi
JDK 10 sneak peek
Martin Toshev
Martin Toshev

@martin_fmi
Who am I
Software consultant (CoffeeCupConsulting)
BG JUG board member (http://jug.bg)
OpenJDK and Oracle RBDMS enthusiast
Twitter: @martin_fmi
Martin Toshev Prague, 19-20 October 2017

@martin_fmi
Agenda
Release overview
Feature highlights
What’s next ?

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JDK 10
•First 6-month cadence release
•An STS (short-term release): end of support in September
•Class File Version Number: 54.0

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JDK 10
• Highlight of the release is the introduction of the var keyword
• A lot of focus put on internal performance and code improvements
• Not so many new features
• Still weak adoption from community (along with JDK 9) at present

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Implemented JEPs
•286: Local-Variable Type Inference
•296: Consolidate the JDK Forest
into a Single Repository
•304: Garbage-Collector Interface
•307: Parallel Full GC for G1
•310: Application Class-Data Sharing
•312: Thread-Local Handshakes
• 313: Remove the Native-Header
Generation Tool (javah)
• 314: Additional Unicode
Language-Tag Extensions
• 316: Heap Allocation
on Alternative Memory Devices
• 317: Experimental Java-Based JIT Compiler
• 319: Root Certificates
• 322: Time-Based Release Versioning

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Other enhancements
•Docker container awareness
•Collections API improvements
•Optional API improvement ( orElseThrow() )
•Removed and deprecated APIs
•Less significant enhancements (such as faster JShell startup and others)

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Feature highlights

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JEP 286: Local-Variable Type Inference
•var keyword introduced in the Java language
•allows developers to reduce the amount of boilerplate code they write
List<String> entities = new LinkedList<String>();
var entities = new LinkedList<String>();

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JEP 310: Application Class-Data Sharing
•Provides a mechanism to reduce memory footprint of class metadata
across JVM processes
•Provides a mechanism to reduce application startup time
•At present supports only classes bundled in JAR files
•Based on the CDS feature introduced in JDK 5 (which works only with the
bootstrap class loader)

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1.Determine application classes for AppCDS archive:
java -XX:+UnlockCommercialFeatures -Xshare:off -XX:+UseAppCDS
-XX:DumpLoadedClassList=application.lst -cp application.jar Main

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2. Generate the AppCDS archive:
java -XX:+UnlockCommercialFeatures -Xshare:dump -XX:+UseAppCDS
-XX:SharedClassListFile=application.lst
-XX:SharedArchiveFile=application.jsa

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3. Run the application with the AppCDS archive:
java -XX:+UnlockCommercialFeatures -Xshare:on -XX:+UseAppCDS
-XX:SharedArchiveFile=application.jsa -cp application.jar Main

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JEP 317: Experimental Java-Based JIT Compiler
•Enables Graal as an experimental JIT compiler on the Linux/x64 platform
-XX:+UnlockExperimentalVMOptions -XX:+UseJVMCICompiler

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Internal performance improvements
•JEP 307: Parallel Full GC for G1
- full GC made parallel
•JEP 312: Thread-Local Handshakes
- optimization techniques allowing to stop individual threads
- enabled by default
- can be disabled:
-XX:ParallelGCThreads=<count>
-XX:ThreadLocalHandshakes=false

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Internal code restructuring
•JEP 296: Consolidate the JDK Forest into a Single Repository
- previously there were child repositories (langtools, jaxp etc.)
- these are now consolidated as part of the root repository
•JEP 304: Garbage-Collector Interface
- changed source structure to allow for easier addition of new GCs
- previous structure didn’t sandbox GCs enough

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JEP 319: Root Certificates
•cacerts file now contains a default set of Cas
•they are part of Oracle’s Java SE Root CA program
keytool -list -v -keystore %JAVA_HOME%jre_10.0.1libsecuritycacerts

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JEP 313: Remove the Native-Header
Generation Tool (javah)
•The javah tool removed from JDK distribution
•javah functionality replaced by enhancements to javac

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JEP 314: Additional Unicode
Language-Tag Extensions
•Java.util.Locale and other APIs (such as java.text.DateFormat) support the
following language-tag extensions:
• cu (currency type)
• fw (first day of week)
• rg (region override)
• tz (time zone)

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JEP 316: Heap Allocation
on Alternative Memory Devices
•Provides the ability to allocate heap space on alternative memory devices
-
XX:AllocateHeapAt=<path>

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JEP 322: Time-Based Release Versioning
•Required due to the 6-month release cadence
•Runtime.Version API enhanced with new methods
•Two new system properties added:
o java.version.date
o java.vendor.version
•Java launcher enhanced to display additional version information

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Docker container awareness
•The JVM is modified to support Docker container awareness
•Proper information (CPU/memory) retrieved from the container rather than
the OS
-XX:-UseContainerSupport

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Docker container awareness
•More options introduced in that regard:
-XX:ActiveProcessorCount=<count>
-XX:InitialRAMPercentage=<percentage>
-XX:MaxRAMPercentage=<percentage>
-XX:MinRAMPercentage=<percentage>

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Optional API
•A new method introduced: orElseThrow()
•A better alternative of get()
Optional x = Optional.ofNullable(null);
x.orElseThrow( () -> {
return new RuntimeException("Optional value is null");});

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Collections API
• New collection API methods that allow the creation of unmodifiable
collections:
List<String> entitiesListCopy = List.copyOf(entitiesList);
Set<String> entitiesSetCopy = Set.copyOf(entitiesSet);
Map<String, String> entitiesMapCopy = Map.copyOf(entitiesMap);
entitiesList.stream().collect(Collectors.toUnmodifiableList());
entitiesSet.stream().collect(Collectors.toUnmodifiableSet());
entitiesMap.entrySet().stream().collect(
Collectors.toUnmodifiableMap(e -> e.getKey(), e -> e.getValue()));

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JDK 11
• Target proposals:
o 309: Dynamic Class-File Constants
o 318: Epsilon: A No-Op Garbage Collector
o 320: Remove the Java EE and CORBA Modules
o 321: HTTP Client (Standard)
o 323: Local-Variable Syntax for Lambda Parameters
o 324: Key Agreement with Curve25519 and Curve448
o 327: Unicode 10
o 328: Flight Recorder
o 329: ChaCha20 and Poly1305 Cryptographic Algorithms
o 330: Launch Single-File Source-Code Programs

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JDK <N>
• Project Panama
• Project Valhalla
• Project Loom
• GraalVM/Truffle
• Project Metropolis
• More to come …

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Summary
• JDK 10 is a milestone for new release cadence of the JDK
• Major highlights: var keyword, AppCDS, Graal JIT experimental support
• Provides performance improvements
• Provides container awareness for JVM applications

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References
JDK 10 enhancement proposals
http://openjdk.java.net/projects/jdk/10/
JDK 10 release notes
http://openjdk.java.net/projects/jdk/10/

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References
JDK 10 Whitepaper
https://developer.oracle.com/devo/res/pdf/1385446602743/Oracle-
Java10.pdf
Java SE 10 final release specification
http://cr.openjdk.java.net/~iris/se/10/latestSpec/

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