What to expect from Java 9?

Ivan KrylovMay 21, 2016

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@JohnWings#J_OnTheBeach

Why talking about it now?

• Less then 1 year till scheduled release

• Now is a good time to plan and prep for it

• I am from Azul Systems - maker of compliant JDKs

• Observing the process from aside, unbiased view on changes

• All sources for this talk are public

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Java 9 and community

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http://wiki.netbeans.org/InternalAPIsUnavailableInJava9

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Subject: module-info.java just causes problems Date: Wed, 4 May 2016 13:33:06 -0500 From: David M. Lloyd <david.lloyd@redhat.com> To: jigsaw-dev <jigsaw-dev@openjdk.java.net>

Tools like Maven and JUnit are yet still having a difficult time coping with the oddball module-info.java file. Can we just drop this thing and let the layer provide metadata for the module? This way of defining module metadata is clearly causing trouble. Reference: all previous arguments from non-Oracle people over the last 5 years or so.

So far none of our software actually functions with Jigsaw, and the prospect is not improving. In the meantime the EG is alternately completely dead or in a state of we'll-register-your-issue-but-cannot-help-resolve-them mode. I'm highly concerned.

Concerns

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“There are only two kinds of languages: the ones people complain about and the ones nobody uses.”

Bjarne Stroustrup

Java Timeline

JDK 6Dec 2006

JDK 7July 2011

JDK 8March 2014

JDK 9exp.

March 2017

JDK 6Nov 2012

JDK 7Apr

2015

JDK 8exp. Mar 2018

J2SE 1.4 Dec 2006

JDK 5Oct 2009

7

GA

EOL

Java EOL & You?

EOL datepassed

Security vulnerabilities

keep appearing&

Sign Support contact

Adopt OpenJDK (Zulu, IcedTea,

homebrew builds)Updated to latest

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What (was) new in Java 8• Lambdas

• Method references

• Type annotations

• Repeated annotations • Interface a.k.a. default

methods

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• Stream API

• Date Time API

• PermGen replacement (vendor specific)

• Nashorn, JavaScript Engine

• new tools (jdeps,jjs,..)

http://www.oracle.com/technetwork/java/javase/8-whats-new-2157071.html

How new features become part of Java standard?

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JEP process

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Source: http://cr.openjdk.java.net/~mr/jep/jep-2.0-02.html

JSR

Source: https://groups.google.com/forum/#!topic/java-social/InafCPMLLaA13

Modules

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Modules

Packages

Classes

fields & methods

Interfaces

…

Abstract Classes

…

Code encapsulation

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Problems being addressed• Java Runtime keep getting bigger and bigger

• Java 8 profiles 1, 2, 3 provide partial solutions

• Jar / Classpath Hell

• What depends on what ..

• Optional dependancies, transitive dependancies

• Lazy class loading and initialisation -> NoClassDefFoundError

• For code that escapes packages the visibility mechanism is poor - only public

• Classes from different packages “see” each other, even from different class loaders

• SecurityManager helps to protect, but it is not on by default16

Jigsaw

JEP 162: Prepare for ModularizationJEP 200: The Modular JDKJEP 220: Modular Run-Time ImagesJEP 201: Modular Source CodeJEP 260: Encapsulate Most Internal APIsJEP 282: jlink: The Java Linker

JSR 376: Java Platform Module SystemJEP 261: Module System

ModularityJava Module

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Example 1s_module/module-info.java

module s_module { exports services; }

p_module/module-info.java

module p_module { requires s_module; }

s_module/services/LocProvider.java

package services; import java.lang.String;

public class LocProvider { public static String getLocation() { return "J on the beach 2016"; } }

p_module/presentations/ModulesDemo.java

package presentations; import services.LocProvider;

public class ModulesDemo { public static void main(java.lang.String[] argv) { System.out.println("I am at “ + LocProvider.getLocation()); } }

Module s_module

Modulep_module

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New params javac/java (1)• # Compile

• >javac -d target -modulesourcepath . s_module/services/LocProvider.java

• >javac -d target -modulepath target -modulesourcepath . p_module/presentations/ModulesDemo.java

• # Run

• >java -mp target -m p_module/presentations.ModulesDemo

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New parameters for javac/java (2)

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• # Packaging

• jar --create --file=jars/s_module.jar -C target/s_module .

• jar --create --file=jars/p_module.jar --main-class=presentations/ModulesDemo -C target/p_module .

• # Run

• $j/bin/java -mp jars -m p_module

Reference: http://openjdk.java.net/projects/jigsaw/quick-start

Example 2./langtools/src/jdk.compiler/share/classes/module-info.java

module jdk.compiler { requires public java.compiler;

exports com.sun.source.doctree; exports com.sun.source.tree; exports com.sun.source.util; exports com.sun.tools.javac; exports com.sun.tools.doclint to jdk.javadoc; exports com.sun.tools.javac.api to jdk.javadoc, jdk.jshell; exports com.sun.tools.javac.code to jdk.javadoc, jdk.jshell; exports com.sun.tools.javac.comp to jdk.javadoc, jdk.jshell; exports com.sun.tools.javac.file to jdk.jdeps, jdk.javadoc; exports com.sun.tools.javac.jvm to jdk.javadoc; exports com.sun.tools.javac.main to jdk.javadoc; exports com.sun.tools.javac.model to jdk.javadoc; exports com.sun.tools.javac.parser to jdk.jshell; exports com.sun.tools.javac.platform to jdk.javadoc; exports com.sun.tools.javac.tree to jdk.javadoc, jdk.jshell; exports com.sun.tools.javac.util to jdk.jdeps, jdk.javadoc, jdk.jshell;

uses javax.annotation.processing.Processor; uses com.sun.source.util.Plugin; uses com.sun.tools.javac.platform.PlatformProvider;

provides com.sun.tools.javac.platform.PlatformProvider with com.sun.tools.javac.platform.JDKPlatformProvider;

provides javax.tools.JavaCompiler with com.sun.tools.javac.api.JavacTool; }

META-INF/services

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Can modularised & non-modularised code co-exist?

• Whatever is in classpath - going into unnamed modules

• Unnamed modules can access all named modules (requires *) /See next slide for a special note/

• The reverse isn’t true - must specify requires unnamed or …

• jar file in -mp automatically being converted to a module with a name matching the name of the jar file

• Therefore referred as automodules

• Provide transition path to jigsaw modules design

• Unnamed modules are being searched for types as a last option 22

Unnamed modules can access all named modules

• Not so true since JDK9 build 118

• These modules are not accessible from unnamed modules:java.activation - java.annotations.common - java.corbajava.transaction - java.xml.bind - java.xml.ws

• One can still add visibility with a flag like `-addmods java.corba`

• Source: May 17th letter from Alan Bateman: http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-May/004309.html

• More info: http://openjdk.java.net/jeps/26123

Types of modules

• Named

• i.e. containing module-info.class

• Automatic

• i.e. jar files placed to the module path

• Unnamed

• contains all types in the classpath

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jdeps -genmoduleinfo

cat /Users/ivan/test/modules/generated/glassfish.corba.omgapi/module-info.java module glassfish.corba.omgapi { requires public java.corba; requires public java.desktop; requires public java.rmi; exports com.sun.corba.ee.org.omg.CORBA; exports javax.rmi.CORBA; exports org.omg.CORBA; exports org.omg.CORBA.DynAnyPackage; exports org.omg.CORBA.ORBPackage; exports org.omg.CORBA.TSIdentificationPackage; exports org.omg.CORBA.TypeCodePackage; exports org.omg.CORBA.portable; exports org.omg.CORBA_2_3; exports org.omg.CORBA_2_3.portable; exports org.omg.CosNaming; exports org.omg.CosNaming.NamingContextExtPackage; exports org.omg.CosNaming.NamingContextPackage; exports org.omg.CosTSInteroperation; exports org.omg.CosTSPortability; exports org.omg.CosTransactions; exports org.omg.Dynamic; exports org.omg.DynamicAny; exports org.omg.DynamicAny.DynAnyFactoryPackage; exports org.omg.DynamicAny.DynAnyPackage; exports org.omg.IOP; exports org.omg.IOP.CodecFactoryPackage; exports org.omg.IOP.CodecPackage; exports org.omg.Messaging; exports org.omg.PortableInterceptor; exports org.omg.PortableInterceptor.ORBInitInfoPackage; exports org.omg.PortableServer; exports org.omg.PortableServer.CurrentPackage; exports org.omg.PortableServer.POAManagerPackage; exports org.omg.PortableServer.POAPackage; exports org.omg.SendingContext; exports org.omg.stub.java.rmi; }

jdeps

-genmoduleinfo ~/test/modules/generated/

glassfish-4.1.1/glassfish/modules/glassfish-corba-omgapi.jar

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jdeps -jdkinternalsglassfish-corba-orb.jar -> java.corba com.sun.corba.ee.impl.copyobject.OldReflectObjectCopierImpl (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.copyobject.OldReflectObjectCopierImpl$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.encoding.BufferManagerWriteStream (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.IIOPInputStream (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.IIOPInputStream$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.IIOPOutputStream (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.IIOPOutputStream$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.ObjectStreamClass (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.ObjectStreamClass$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.ObjectStreamField (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.ObjectStreamField$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.presentation.rmi.JNDIStateFactoryImpl$1 (glassfish-corba-orb.jar) -> com.sun.jndi.cosnaming.CNCtx JDK internal API (java.corba) com.sun.corba.ee.impl.util.JDKClassLoader (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.util.JDKClassLoader$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba)

jdeps

-jdkinternals

glassfish/ modules/ glassfish-corba-orb.jar

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java -XaddExportsjava -XaddExports :java.base/sun.security.provider=ALL-UNNAMED, java.base/sun.security.pkcs=ALL-UNNAMED, java.base/sun.security.util=ALL-UNNAMED, java.base/sun.security.x509=ALL-UNNAMED, :

java -XaddReads-XaddReads:java.management=testng

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• Consider an app with extensions

• The extension might require a different version of a module than loaded before

• The extension might require service providers

• Layer of modules encapsulates

• a module graph

• mapping from each module in that graph to a class loader

• Boot layer - created by vm at start time and suitable for most apps

• App can create a new layer - new universe of modules

• Stackable - package resolution starts with the app layer and goes down to the boot layer

Layers

Modularity

Source: http://openjdk.java.net/projects/jigsaw/doc/jdk-modularization.html

JDK 7 b65 JDK 8 b48JDK9 EA

29http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html

More to discover

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• Reflection. java.lang.reflect.Module class.

• multirelease jar (Since b109. Bug 8132734)

• Packages with the same name possibly leading to NoClassDefFoundException

• Layers - new concept for classloaders

• New instruments for modules development

• <java9_jigsaw>/bin/jdeps -help

• IDE are now supporting modules

• Classloaders and ways for circular dependancies between modules

Jigsaw - Unresolved issueshttp://openjdk.java.net/projects/jigsaw/spec/issues/

• Module declarations

• #ModuleNameSyntax · #CompileTimeDependences · #ModuleAnnotations

• Module artifacts

• #MultiModuleExecutableJARs · #MultiModuleJARs · #ReifiedModuleGraphs

• Module descriptors

• #StandardModuleAttributes

• Module graphs

• #CyclicDependences

• Reflection

• #ClassFilesAsResources · #ResourceEncapsulation · #ReflectiveAccessToNonExportedTypes · #ReflectionWithoutReadability

• Class loaders

• #AvoidConcealedPackageConflicts · #PlatformClassLoader

• Versioning

• #StaticLayerConfiguration · #MultipleModuleVersions · #VersionsInModuleNames · #VersionedDependences

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(My) takeaways on Java 9 modules• Purpose - explicit listing of dependancies

• OSGi compatible and complementary

• Will provide new optimisation paths

• Compatible with jar/cp

• jigsaw - rough flight all way along, loosing features

• lost ability to match versions 32

Jigsaw - links• If you google it - discard all posts before 2014, probably even before 2015 too

• State of Jigsaw (March 8 2015)

• http://openjdk.java.net/projects/jigsaw/spec/sotms/

• JavaOne 2015 (also Devoxx BE)

• http://openjdk.java.net/projects/jigsaw/j1/

• Code was integrated in JDK9 EA build 111

• See also: http://blog.codefx.org/java/dev/features-project-jigsaw-java-9/

• http://blog.codefx.org/java/dev/javaone-2015-under-the-hood-of-project-jigsaw/33

Syntax changes - Milling Project Coin• Private default methods

interface I { void a() { /*Common code*/ ; /*a’s specific code*/ } void b() { /*Common code*/ ; /*b’s specific code*/ } private void c() { /*Common code*/ ; } }

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interface II { private void foo_private(String s); // Error: private method must declare body. private abstract void foo_abstract(int i, int j); // Error: private & abstract: bad combo void foo_decl(int x); // OK. private I foo_with_body() { return null; } // OK. }

Syntax changes - Milling Project Coin

• Effectively-final variables in try-with-resources expressions

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public static void main(String... args) throws …{ FileReader f = new FileReader(“test.txt”); br =new BufferedReader(fr); try (br) { // do something } catch (Exception ex) { } }

public static void main(String... args) throws …{ FileReader f = new FileReader(“test.txt"); try (br =new BufferedReader(fr)) { // do something } catch (Exception ex) { } }

Syntax changes - Milling Project Coin• @SafeVarargs in private methods

class VarargsFinalOnly { @SafeVarargs private void m(List<String>... args) { }}

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public class TypeInferrenceTest { Map<String, String> map = new HashMap<String, String>() { { map.put("key", "value"); } }; }

• Using diamond with anonymous classes when actual type may be deduced

public class TypeInferrenceTest { Map<String, String> map = new HashMap<> () { { map.put("key", "value"); } }; }

Syntax changes - Milling Project Coin

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Prior to Java 9./TypeInferrenceTest.java:7: error: cannot infer type arguments for HashMap<K,V> new HashMap<>() ^ reason: cannot use '<>' with anonymous inner classes where K,V are type-variables: K extends Object declared in class HashMap V extends Object declared in class HashMap 1 error

http://c2.com/cgi/wiki?DoubleBraceInitialization

Syntax changes - Milling Project Coin• Can’t use single _ as a name

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// key: compiler.warn.underscore.as.identifier // options: -source 8 -Xlint:-options

class UnderscoreAsIdentifierWarning { String _ = null;}

Process API Updates• JEP 102: Process API Updates

• New:

• Get pid for this JVM

• Get list of processes

• Operations on trees of processes

Source: http://blog.takipi.com/java-9-the-ultimate-feature-list/

Process proc = Runtime.getRuntime() .exec(new String[]{"/bin/sh", "-c", "echo $PPID"}); if (proc.waitFor() == 0) { InputStream in = proc.getInputStream(); int available = in.available(); byte[] outputBytes = new byte[available]; n.read(outputBytes); String pid = new String(outputBytes); System.out.println("Your pid is " + pid); }

System.out.println("Your pid is " + ProcessHandle.current().getPid());

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Spin Loop Hint• JEP 285: Spin-Wait Hints

• Scope: latency & performance

• Features:

• New method j.l.Thread.onSpinWait()

• Just a hint

• on x86 - translates into the ‘pause’ instruction

class EventHandler { volatile boolean eventNotificationNotReceived; void waitForEventAndHandleIt() { while ( eventNotificationNotReceived ) { java.lang.Thread.onSpinWait(); } readAndProcessEvent(); } void readAndProcessEvent() { // Read event from some source and process it . . . } }

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Producer/Consumer and SLH

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Spin Loop Hint• Cool. I have spin loops. Wait for 9?

• Just include the agrona library

• or look at java/org/agrona/hints/ThreadHints.java

• Works for older JDKs

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https://github.com/real-logic/Agrona/blob/master/src/main/java/org/agrona/hints/ThreadHints.java

JShell• Project `Kulla

• http://openjdk.java.net/projects/kulla/

• In main trunk since JDK 9 EA build 90

• REPL as you know it for other languages

• Helps teaching Javaclass HelloWorld { public static void main(String[] args) { System.out.println("Hello World!"); } }

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Jshell Demo

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JShell - examples• > ./images/jdk/bin/jshell

• -> String s=new String("hello");

• | Added variable s of type String with initial value “hello”

• -> new String("hello");

• | Expression value is: "hello"

• | assigned to temporary variable $1 of type String

• -> System.out.println($1);

• h

• -> ello

• -> System.out.println(“hello”); System.out.flush();

• hello45

Garbage First is on by default• Pros

• State-of-the-art GC in HotSpot (albeit being 10+ years old)

• Regional parallel concurrent collector

• Targeting both low pause and high throughput

• Default => Great number of users => Bugs detecter sooner => G1 will become even more robust shortly

• Cons

• Due to different characteristics it may reveal synchronisation problems in the code

• Eve after 9 years G1 has bugs with Cassandra, Elasticsearch, Lucene, perhaps, other ones are yet not discovered?

• source (dated July 2015): https://groups.google.com/forum/#!topic/mechanical-sympathy/JxsuVtIIOaY

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Surviving the change of default GC• If you used no i.e. default GC settings

• capture the ergonomics at your deployment sites

• consider explicitly setting GC flags in all deployment scripts

• If you already had selected and tuned GC flags

• No changes, old collectors not phasing out

• In any case - keep trying G1

• Understand how GC works

• Basic algorithms and associated metrics

• More reading: http://www.infoq.com/minibooks/java-garbage-collection47

New JEPs briefly. Performance

• 193: Variable Handles

• 143: Improve Contended Locking

• 266: More Concurrency Updates

• 197: Segmented Code Cache

• 165: Compiler Control

• 243: Java-Level JVM Compiler Interface

• 246: Leverage CPU Instructions for GHASH and RSA

• 250: Store Interned Strings in CDS Archives

• 254: Compact Strings

• JEP 280: Indify String Concatenation

• 230: Microbenchmark Suite48

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Unified JVM Logging• For better diagnostics, uniform across all components• 6 levels of logging x dozens of tags • Output to stdout / stderr / file / rotating file • No more badly interleaved lines• -Xlog:help• 11 decorators

-Xlog:classinit -Xlog:classloaderdata -Xlog:defaultmethods -Xlog:itables -Xlog:monitormismatch -Xlog:safepoint -Xlog:startuptime -Xlog:vmoperation -Xlog:vtables -Xlog:verification

-XX:+TraceClassInitialization -XX:+TraceClassLoaderData -XX:+TraceDefaultMethods -XX:+TraceItables -XX:+TraceMonitorMismatch -XX:+TraceSafepoint -XX:+TraceStartupTime -XX:+TraceVMOperation -XX:+PrintVtables -XX:+VerboseVerification

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JEP 223: New Version-String Scheme• System Property Existing Proposed • ------------------------------- ------------ -------- • Early Access • java.version 1.9.0-ea 9-ea • java.runtime.version 1.9.0-ea-b73 9-ea+73 • java.vm.version 1.9.0-ea-b73 9-ea+73 • java.specification.version 1.9 9 • java.vm.specification.version 1.9 9

• Major (GA) • java.version 1.9.0 9 • java.runtime.version 1.9.0-b100 9+100 • java.vm.version 1.9.0-b100 9+100 • java.specification.version 1.9 9 • java.vm.specification.version 1.9 9

• Minor #1 (GA) • java.version 1.9.0_20 9.1.2 • java.runtime.version 1.9.0_20-b62 9.1.2+62 • java.vm.version 1.9.0_20-b62 9.1.2+62 • java.specification.version 1.9 9 • java.vm.specification.version 1.9 9

• Security #1 (GA) • java.version 1.9.0_5 9.0.1 • java.runtime.version 1.9.0_5-b20 9.0.1+20 • java.vm.version 1.9.0_5-b20 9.0.1+20 • java.specification.version 1.9 9

New JEPs briefly. What’s going away?• 231: Remove Launch-Time JRE Version Selection

• 240: Remove the JVM TI hprof Agent

• 241: Remove the jhat Tool———————————

• Because of modules (JEP - 261)

• -Xbootclasspath & -Xbootclasspath/p

• system property sun.boot.class.path

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New JEPs briefly. Client/graphics• 258: HarfBuzz Font-Layout Engine

• 263: HiDPI Graphics on Windows and Linux

• 265: Marlin Graphics Renderer

• 262: TIFF Image I/O

• 257: Update JavaFX/Media to Newer Version of GStreamer (1.4.4)

• 251: Multi-Resolution Images

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New JEPs briefly. Security

• 219: Datagram Transport Layer Security (DTLS)

• 229: Create PKCS12 Keystores by Default

• 244: TLS Application-Layer Protocol Negotiation Extension

• 249: OCSP Stapling for TLS

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Azul Systems• Zing: A better JVM for the enterprise

• Azul’s innovative Java runtime for business applications• Certified Java SE builds• Removes GC as a factor in your operation• Supports large in-memory data stores• Solves Java’s “warm-up” problem• Runs on distros of RHEL, Ubuntu, SLES and CentOS

•Zulu: Java when all you need is Support • Free and Open Source (based on OpenJDK)• Certified Java SE builds• Runs on Windows, Linux & Mac• Performance parity with Oracle Hotspot• Optional customized “embedded” offerings

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Unicode in Java 9

• 227: Unicode 7.0…

• … & 267: Unicode 8.0

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Conclusions

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Thanks

Q&A

@JohnWings

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Backup on @SafeVarargs @SafeVarargs // Not actually safe!

static void m(List<String>... stringLists) {

Object[] array = stringLists;

List<Integer> tmpList = Arrays.asList(42);

array[0] = tmpList; // Semantically invalid, but compiles without warnings

String s = stringLists[0].get(0); // Oh no, ClassCastException at runtime!

}

that’s it

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