Introduction to Java 7 (Devoxx Nov/2011)

The WGJD - Intro to Java 7
Ben Evans and Martijn Verburg
(@kittylyst @karianna)

http://www.teamsparq.net

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

Saturday, 24 December 11 1

This is not an Oracle legal slide

2


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

3


Who are these two anyway?

4


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

5


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

6


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

8


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

9


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

10


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

23


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

30


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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Original Image by Acaben

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

35


What? You still here?
Go take a break will you!

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Introduction to Java 7 (Devoxx Nov/2011)

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