What to Expect from Java 9

What to expect from Java 9?
Ivan Krylov

May 21, 2016
1
@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
2

4
http://wiki.netbeans.org/InternalAPIsUnavailableInJava9

5
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

6
“There are only two kinds of languages:  
the ones people complain about and the ones nobody uses.”
Bjarne Stroustrup

Java Timeline
JDK 6 
Dec 2006
JDK 7 
July
2011
JDK 8 
March
2014
JDK 9 
exp.
March
2017
JDK 6 
Nov 2012
JDK 7 
Apr
2015
JDK 8 
exp.
Mar
2018
J2SE 1.4 
Dec 2006
JDK 5 
Oct 2009
7
GA
EOL

Java EOL & You?
EOL date

passed

Security
vulnerabilities

keep appearing
&
Sign Support
contact
Adopt OpenJDK
(Zulu, IcedTea,
homebrew builds)
Updated to latest
JDK
8
Updates needed

Java 9 schedule (tent.)Featurecomplete
ZeroBugBounce
Rampdownphase2
FinalReleaseCandidate
May’16
Alltestsrun
RampdownStart
GeneralAvailability
Aug’16
Sept’16
Oct’16
Dec’16
Jan’17
Mar’17
9

What (was) new in Java 8
• Lambdas

• Method references

• Type annotations

• Repeated annotations

• Interface a.k.a. default
methods

10
• 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?
11

JEP process
12
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
Packages
Classes
ﬁelds &
methods
Interfaces
…
Abstract
Classes
…
Code encapsulation
15

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 default
16

Jigsaw
JEP 162: Prepare for Modularization

JEP 200: The Modular JDK 
JEP 220: Modular Run-Time Images

JEP 201: Modular Source Code

JEP 260: Encapsulate Most Internal
APIs

JEP 282: jlink: The Java Linker 
JSR 376: Java Platform Module System

JEP 261: Module System 
ModularityJava Module
17

Example 1
s_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
Module
p_module
18

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
19

New parameters for javac/java (2)
20
• # 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
21

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.corba 
java.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/261
23

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
24

25
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

26
jdeps -jdkinternals
glassfish-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)
com.sun.corba.ee.impl.encoding.BufferManagerWriteStream (glassfish-corba-orb.jar)
com.sun.corba.ee.impl.io.IIOPInputStream (glassfish-corba-orb.jar)
com.sun.corba.ee.impl.io.IIOPInputStream$1 (glassfish-corba-orb.jar)
com.sun.corba.ee.impl.io.IIOPOutputStream (glassfish-corba-orb.jar)
com.sun.corba.ee.impl.io.IIOPOutputStream$1 (glassfish-corba-orb.jar)
com.sun.corba.ee.impl.io.ObjectStreamClass (glassfish-corba-orb.jar)
com.sun.corba.ee.impl.io.ObjectStreamClass$1 (glassfish-corba-orb.jar)
com.sun.corba.ee.impl.io.ObjectStreamField (glassfish-corba-orb.jar)
com.sun.corba.ee.impl.io.ObjectStreamField$1 (glassfish-corba-orb.jar)
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)
com.sun.corba.ee.impl.util.JDKClassLoader$1 (glassfish-corba-orb.jar)
jdeps
-jdkinternals
glassfish/
modules/
glassfish-corba-orb.jar

27
java -XaddExports
java -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

28
• 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 b65JDK 8 b48JDK9 EA
29
http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html

More to discover
30
• 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 issues

http://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
31

(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*/ ; }
}
34
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.
}

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

35
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) {
}
}

• @SafeVarargs in private methods
class VarargsFinalOnly {
@SafeVarargs private void m(List<String>... args) { }
}
36

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");
}
};
}
37
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

•
Can’t use single _as a name
38
// 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());
39

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
. . .
}
}
40

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

42
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 Java
class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
43

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();
• hello
45

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
46

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-collection
47

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 Suite
48

49
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

50
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
• 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
• 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

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

51

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
52

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
53

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
54

Unicode in Java 9
• 227: Unicode 7.0…

• … & 267: Unicode 8.0
55

58
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!
}

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