java8 - under the hood

© 2011 IBM Corporation

Java8 – under the hood

Lakshmi Narasimhan ([email protected])

Java Technology Center

mailto:[email protected]


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Agenda

Java eco-systemFeatures at a GlanceModularity in JavaLambda ExpressionsQ&A


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Disclaimer

Opinions/views expressed here are my own and should not be taken as IBM’s views.

Java8 is still under development and so ….


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Important Disclaimers

THE INFORMATION CONTAINED IN THIS PRESENTATION IS PROVIDED FOR INFORMATIONAL PURPOSES ONLY. WHILST EFFORTS WERE MADE TO VERIFY THE COMPLETENESS AND ACCURACY OF THE INFORMATION CONTAINED IN THIS PRESENTATION, IT IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED. ALL PERFORMANCE DATA INCLUDED IN THIS PRESENTATION HAVE BEEN GATHERED IN A CONTROLLED ENVIRONMENT. YOUR OWN TEST RESULTS MAY VARY BASED ON HARDWARE, SOFTWARE OR INFRASTRUCTURE DIFFERENCES.ALL DATA INCLUDED IN THIS PRESENTATION ARE MEANT TO BE USED ONLY AS A GUIDE.IN ADDITION, THE INFORMATION CONTAINED IN THIS PRESENTATION IS BASED ON IBM’S CURRENT PRODUCT PLANS AND STRATEGY, WHICH ARE SUBJECT TO CHANGE BY IBM, WITHOUT NOTICE. IBM AND ITS AFFILIATED COMPANIES SHALL NOT BE RESPONSIBLE FOR ANY DAMAGES ARISING OUT OF THE USE OF, OR OTHERWISE RELATED TO, THIS PRESENTATION OR ANY OTHER DOCUMENTATION. NOTHING CONTAINED IN THIS PRESENTATION IS INTENDED TO, OR SHALL HAVE THE EFFECT OF: - CREATING ANY WARRANT OR REPRESENTATION FROM IBM, ITS AFFILIATED COMPANIES OR ITS OR THEIR SUPPLIERS AND/OR LICENSORS


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Java eco-system Proliferation of Java

– At least 15 known proprietary JVMs– >30 Free and open source implementations

OpenJDK– OpenJDK is the Reference Implementation of J2SE Spec– More open participation through OpenJDK– Lot of big weights behind OpenJDK (IBM, Twitter, RedHat, SAP ..)– Release Cadence

Newer/simpler programming paradigms– Combine the best of interpreted and compiled languages– Allow for rapid prototyping and development

MMP and Cloud scale architectures– Thousands of “Clustered” JVMs– “Cloud aware” Vms– Network and memory no longer the constraints – but Java's awareness

of it is


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Java8 – features at a glance *Performance

Parallel Array Sorting Concurrency updates (JSR 166e) Charset implementation improvements

Modularity and Manageability Java Platform Module System Java Platform Module System (aka jigsaw)(aka jigsaw)

Ease of use Lambda Expressions Lambda Expressions (aka “Closures”/anonymous inner classes)(aka “Closures”/anonymous inner classes) Bulk data operations for collections Generalized Target-Type Inference Repeating annotations Date and time API

UI and “currency” updates Javadoc support through javax.tools Adopt unicode CLDR Data Unicode 6.1 Launch JavaFX applications

* Bound to change – For detailed list see http://openjdk.java.net/jeps/0


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Java8 - What’s out

Mtoolkit– Only XtoolKit (*nix) and WtoolKit (Windows) supported– Impact - Minimal

IO code page converters– sun.io.* classes removed– Deprecated in JDK7– Switch to NIO for all code-page conversion– Impact – High

“apt” tool– Deprecated in JDK7– Tool, associated API and docs will be removed– Users to switch to JSR269 (Pluggable Annotation Processing API)– Impact - Moderate

Watch out for modularity


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JDK8 Features - PerformanceParallel Array Sorting: Current sorting algorithms (in Collections and Arrays) are sequential Modified internally to use Fork/Join framework Sorting will still be synchronous Adds a default ForkJoin Pool to be used by both internal classes and applications

Read More : – http://openjdk.java.net/jeps/103


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JDK8 Features - PerformanceConcurrency updates Scalable updatable variables Cache-oriented enhancements to the ConcurrentHashMap API

– Less footprint (comparable to HashMap)– Better performance under concurrent load

ForkJoinPool improvements Additional Lock and Future classes and better support for software transactional

memory (STM) frameworks. Read More :

– http://openjdk.java.net/jeps/103

Charset Improvements:• Decrease the size of installed charsets• Reduce maintenance cost by generating charset implementations at build time

from simple text-based mapping tables• Improve the performance of encoding/decoding

http://openjdk.java.net/jeps/103


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Java Platform Module System

Enabling the IBM Blue Stack with Java

© 2010 IBM Corporation11

Modularity exists at App level (only) Work around inefficiencies in underlying

layer Application migration is a pain

Do you remember your class path sequencing? Has led to tools like Maven

The JVM knows everything about the

application and its usage“one-size fits all” doesn't scale


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JDK8 Features – Java Platform Module SystemMotivations

Jar Hell– Excellent distribution format– Poor versioning format– “jar” format is outdated– No way to reliably specify and manage dependencies– Currently worked around at deployment stage

Monolithic JDK– Delivered as one massive, indivisible artifact– Inter-dependencies between J2SE components– Increased start-up, footprint, download time

“Profile” based usage– A simple “Hello World” program internally loads > 300 classes– Load only those classes that are needed by application

• Why do I need to load a “javax.swing” for a OLTP app??– Merging J2SE and J2ME

Expose “modularity” to applications– Modularize the entire stack and not just application– Inter-op with existing modularity frameworks


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JDK8 Features – Java Platform Module SystemDesign Principles and Definitions

Modularity is a language construct Module boundaries are strictly enforced Static, single-version module resolution is usually sufficientDefinitions Module -Collection of Java types (i.e., classes and interfaces) with a name, an optional

version number and a formal description of its relationships to other modules. A module may be platform specific and embody native code.

Resolution - Process of locating additional modules, as required, and constructing a superset of that set in which every dependence is optimally satisfied.

Phases - – Compile time – A module’s dependences are resolved, its types are compiled from Java source files,

and its other content is compiled or constructed as appropriate. The results are then packaged up for publication and distribution.

– Install time – A module is inserted into a module library, i.e., a collection of previously-installed modules. If the module is invokable, i.e., it has an entry point, then it is made ready for use by resolving its dependences and storing the result of that computation in a persistent configuration.

– Run time – An invokable module is loaded into a running Java virtual machine and linked up to the other modules upon which it depends as recorded in its configuration during installation.


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JDK8 Features – Java Platform Module System

Anatomy of a Module

Source code for module-info.java


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JDK8 Features – Java Platform Module System

Module nameModule Version

Anatomy of a ModuleDependent Module

Dependent Module with specific version

What does this module provide to others

Main method in this module


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JDK8 Features – Java Platform Module SystemCompiling and installing modules

1) javac now understands “modulepath” keyword – use when compiling multiple modules

2) Create a repository deploy your modules

3) Install your module into the repository

4) Run your app


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JDK8 Features – Java Platform Module SystemDifferences between Jigsaw and OSGi

Static resolution – Module dependencies are resolved at module install time and not run-time

– More predictable– Faster class loading

Meta data– Jigsaw uses module-info.class– OSGi uses readable MANIFEST.MF

Dependency boundary– Modules for jigsaw– Packages for OSGi

Unit of sharing– Modules for jigsaw (packages can span modules)– Packages for OSGi


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JDK8 Features – Java Platform Module SystemWhat it means to you?

No more “non-standard” API access (sun.*)– Visibility might be enforced by module boundary

No more single “rt.jar” Faster start up time Easier dependency resolution

– At compiler, install time and not run-time– Quicker migration

Custom distributable formats??

To the JDK Developers?


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JDK8 Features – Java Platform Module SystemFrom this


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JDK8 Features – Java Platform Module SystemTo this...


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JDK8 Features – Lambda ExpressionsSupport for operating on an arbitrary "block of Java code", or body, which is either a

statement list, an expression, or a combination of both.Implementation of JSR 335

Background Consider the ActionListener Interface (an eg of functional interface a.k.a SAM)

http://cr.openjdk.java.net/~briangoetz/lambda/lambda-state-4.html

“Call-back” interfaces are not uncommon (remember Runnable, Comparator?) Too much boiler plate without adding value


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JDK8 Features – Lambda ExpressionsEnter Java8 style:

Lambda syntax & Examples

Argumentlist → body()

Examples:


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JSR 335 – Adding Lambda expressions to the Java Language


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JDK8 Features – Lambda Expressions – parting thoughts

http://jcp.org/aboutJava/communityprocess/ec-public/materials/2011-01-1112/2011-01_JCP_EC_ProjectLambda.pdf


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Where to go next?• Read the documentation

• Download the SDK

• Write/break the code

• Prepare for migration

• Give feedback

• Join the “Java Technology Community” - http://bit.ly/a7KpQj

http://bit.ly/a7KpQj


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Questions?

https://espresso.hursley.ibm.com/perl/secure/fetch/j9-60/Other/pxi32hs60/20090206_02/pxi32hs60-20090206_02-hsdk.jar


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Reference

List of propsed enhancements to jdk8 : http://openjdk.java.net/jeps/0

Modularity:Massive monolithic JDK - http://mreinhold.org/blog/massive-monolithic-jdk

Project jigsaw: Big picture : http://cr.openjdk.java.net/~mr/jigsaw/notes/jigsaw-big-picture-01

What's cooking in jdk 8 : http://www.javacodegeeks.com/2012/05/whats-cooking-in-java-8-project-jigsaw.html

Jigsaw quick start : http://openjdk.java.net/projects/jigsaw/doc/quickstart.html

Lambda Expressions:Project lambda homepage: http://openjdk.java.net/projects/lambda/

Enhanced collection APIs : http://www.javabeat.net/2012/05/enhanced-collections-api-in-java-8-supports-lambda-expressions/

Project lambda - multicore and beyond : http://jcp.org/aboutJava/communityprocess/ec-public/materials/2011-01-1112/2011-01_JCP_EC_ProjectLambda.pdf

http://openjdk.java.net/jeps/0

http://mreinhold.org/blog/massive-monolithic-jdk

http://cr.openjdk.java.net/~mr/jigsaw/notes/jigsaw-big-picture-01

http://www.javacodegeeks.com/2012/05/whats-cooking-in-java-8-project-jigsaw.html

http://openjdk.java.net/projects/jigsaw/doc/quickstart.html

http://openjdk.java.net/projects/lambda/

http://www.javabeat.net/2012/05/enhanced-collections-api-in-java-8-supports-lambda-expressions/