Slide Design by http://www.kerrykenneally.com

The WGJD - Intro to Java 7

Ben Evans and Martijn Verburg (@kittylyst @karianna)

http://www.teamsparq.net

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This is not an Oracle legal slide

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No, we’re not in sales!

• Directors of TeamSparq– “Optimisation for Technical Teams”– Ben is known for his performance & concurrency work– Martijn is the “Diabolical Developer” and Ben can be just as ‘evil’

• Authors of “The Well-Grounded Java Developer”

• Co-Leaders of the LJC (London’s Java User Group)– Hold a seat on the JCP SE/EE Executive Committee

• Regular conference speakers– JavaOne, Devoxx, OSCON, etc

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Who are these two anyway?

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How this university session is going to work

• This is a fact!– This is an opinion

• This session may be a little different to advertised...– Being a “Well-Grounded Java Developer” changes over time

• This session will go fairly quickly– But the slides will be made available– And you can always get hold of us for any questions

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Timetable

• Introduction to Java 7 (~35 mins)

• BREAK (5 minutes)

• Polyglot and functional programming (~50 mins)

• BREAK (5 minutes)

• Modern Java Concurrency (~60 mins)

• Conclusion and Extra Q&A

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Real Developers code through bathroom breaks

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The Well-Grounded Java Developer...

• Is not just a Java language whizz– Understands the basics of the JVM– Understands software development is a social activity– Utilises software craftsmanship approaches– Understands architecture

• Is looking at Java 7•

• Is looking at polyglot and functional programming

• Is looking at modern concurrency practices

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Java 7 - Why is it important

• The WGJD wants to code rapidly

• The WGJD wants to code concisely

• The WGJD wants to take advantage of:– The compiler (including JIT)– The JVM

• Java 7 gives you many improvements in these areas

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OpenJDK - The Java 7/8 split

• 20 Sep 2010 - Mark Reinhold announces Plan B– Splits OpenJDK effort into Java 7 (July 2011) and Java 8 (2013)– Popular choice with the community

• July 2011 - Java 7 goes gold

• Some new features to be delayed until JDK 8– Closures Lambdas SAM literals– Modularisation (aka Jigsaw)

• JRockit features to be merged into OpenJDK– Enhanced management of the JVM– Ongoing merge of the VM engineering groups

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Contents of JDK 7 Release

• Project Coin

• NIO.2

• Method Handles

• invokedynamic

• Concurrency Refresh

• Odds & Ends

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Project Coin

• “Small” changes

• Language Level, not VM

• Stay away from the type system

• Developed in a very OSS manner– Was an ‘interesting’ experience for all involved

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Project Coin - Highlights

• Strings in switch

• try-with-resources (aka ARM or TWR)

• Diamond Syntax

• Multicatch with precise rethrow

• Enhanced syntax for numeric literals

• Varargs / autoboxing warning

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Strings in switch

• Code along exercise: FeedingSchedule.java

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try-with-resources

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Diamond syntax

• Code along exercise: HordeOfOtters.java

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Personally I’d stick to Java 1.4

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NIO.2 - New I/O version 2

• A new file system and path abstraction

• Based on Path– An abstract view of a ‘file like’ system

• Files class contains many helper methods, including– File manipulation (copy, move, rename etc)– Walking directory trees– Native file system support (e.g. symbolic links)

• Works with existing java.io.File code

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NIO.2 - New I/O version 2

• Asynchronous (non-blocking) I/O

• For sockets and files

• Mainly utilises java.util.concurrent.Future

• New NetworkChannel– Socket/Channel construct– Binding, options and multicast

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Path and Files - Some examples

• Code along exercise: Housekeeping.java

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URL stream to file - Java 6 style NIO

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URL stream to file in Java 7

• Code along exercise: VetNotes.java

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NIO.2 - Future base file I/O

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Monty Python eat your heart out

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Method Handles

• We already have Reflection API– It’s all pretty horrible

• JDK 7 introduces a new way to inspect at runtime

• Method Handles– Represent the ability to call a method– Implement a subclass of java.lang.invoke.MethodHandle– Are strongly-typed and typesafe– Needed for invokedynamic - but also used standalone

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Example - ThreadPoolManager

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Cancelling using Reflection

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Cancelling using MethodHandle

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invokedynamic

• invokedynamic is a key new JVM feature– It’s the first new bytecode since Java 1.0– Joins invokevirtual, invokestatic, invokeinterface and

invokespecial

• Relaxes a key part of the static typing system– User code can determine dispatch at runtime

• Aims to be as fast as regular method dispatch– e.g. invokevirtual

• No Java syntax in Java 7– But maybe for Java 8

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invokedynamic contd.

• JRuby, Jython, Groovy, Clojure et al all benefit– JRuby gains a lot, Clojure not so much– Even Scala is using it now!

• JRuby has been working closely with the JSR-292 team– Big wins– Makes JRuby enticing to Ruby developers

• Java 8 also gets a boost– Lambdas have a much nicer design with invokedynamic

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Other JVM Languages?

Meh - Use the Golden Hammer!

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Java 7 Concurrency Refresh

• Java 7 has a number of new concurrency toys

• The headline item is Fork / Join– similar to MapReduce, useful for a certain class of problems– fork and join executions are not necessarily threads

• We’ll cover this in the final hour!

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Java 7 - That’s not all

• Nimbus Look & Feel for Swing

• New helper classes including Objects– .deepEquals() and friends

• Enhanced JDBC (including try-with-resources support)

• Better unicode support– Thanks in part to Tom Christiansen of Perl fame

• More small changes in niche areas

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New Faces in the OpenJDK

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What We Didn’t Have Time To Talk About

• Java 8– Java FX 2.0

• Java EE 6/7

• Java ME– Android and _that_ lawsuit

• OpenJDK changes & JDK Enhancement Proposals (JEP)

• Java Community Process (JCP)– Java Specification Requests (JSRs)– Java User Groups (JUGs) and reinvigorating the Community

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What? You still here?

Go take a break will you!

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