Slide Design by http://www.kerrykenneally.com The WGJD - Intro to Java 7 Ben Evans and Martijn Verburg (@kittylyst @karianna) http://www.teamsparq.net 1 Saturday, 24 December 11
May 12, 2015
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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