OSCON 2012 tutorial session Part I

1. The Well-Grounded Java Developer
Introduction to Java 7

2. This is not an Oracle legal slide
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3. No, we’re not in sales!
• Get in touch
- Ben is: @kittylist
- Martijn is: @karianna (and @diabolicaldev)
• What we do
- Authors of “The Well-Grounded Java Developer”
- CEO/CTO of jClarity - JVM/Hardware/Performance stuff
• We co-lead the LJC (London’s Java User Group)
- Hold a seat on the JCP SE/EE Executive Committee
- Run Adopt a JSR and Adopt OpenJDK programmes

4. Or in pictures...

5. How this session is going to work
• 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
• There are USB keys going around
- Copy over the WGJD into $WORKSPACE
- Install Java 7 if you haven't done so already!
- Your major IDEs should work
• Pair/Group programming works best
- Have the least experienced person do the actual typing!

6. Attempted Timetable
Introduction to Java 7 - 0900-0955 (~55 mins)
– BREAK (5 minutes)
Polyglot and functional programming - 1000-1030 (~30 mins)
BREAK (30 minutes)
Polyglot and functional programming - 1100-1125 (~25 mins)
– BREAK (5 minutes)
Modern Java Concurrency - 1130-1230(~60 mins)

7. Real developers code through
bathroom breaks
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8. 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 physical and logical architectures
• Is using Java 7
- At least at home if not at work
• Is looking at polyglot and functional programming
• Is looking at modern concurrency practices

9. 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 (including GC)
• Java 7 gives you many improvements in these areas

10. OpenJDK - The Java 7/8 split
• 20 Sep 2010 - Mark Reinhold announces Plan B
- Splits OpenJDK plan into Java 7 (July 2011) & Java 8 (2013)
- Popular choice with the community
• July 2011 - Java 7 goes gold
- Wow, a whole year ago now!
• Some new features to be delayed until JDK 8
- Lambda Expressions
- Modularisation (aka Jigsaw)
• JRockit features to be merged into OpenJDK
- Enhanced management of the JVM
- Ongoing merge of the VM engineering groups

11. Contents of JDK 7 Release
Project Coin
NIO.2
Method Handles
invokedynamic
Concurrency Refresh
Odds & Ends

12. 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

13. Project Coin - Highlights
Strings in switch
try-with-resources (aka ARM or TWR)
Diamond Syntax
Multi-catch with precise re-throw
Enhanced syntax for numeric literals
Varargs / autoboxing warning

14. Strings in switch
• Code along exercise: FeedingSchedule.java

15. try-with-resources

16. Diamond syntax
• Code along exercise: HordeOfOtters.java

17. Personally I’d stick to Java 1.4
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18. 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

19. 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

20. Path and Files - Some examples
• Code along exercise: Housekeeping.java

21. URL stream to file - Java 6 style NIO

22. URL stream to file in Java 7
• Code along exercise: VetNotes.java

23. NIO.2 - Future base file I/O
• See ExceptionExamples.java as well (multi-catch)

24. 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 subclass java.lang.invoke.MethodHandle
- Are strongly-typed and typesafe
- Needed for invokedynamic - but also used standalone

25. Example - ThreadPoolManager

26. Cancelling using Reflection

27. Cancelling using MethodHandle

28. 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

29. 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 works closely with the JSR-292 team
- Charlie Nutter (winner of JAX special jury award)
- Big wins
- Makes JRuby enticing to Ruby developers
• Java 8 also gets a boost
- Lambdas will be implemented with invokedynamic

30. Other JVM Languages?
Meh - Use the Golden Hammer!
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31. Java 7 Concurrency Refresh
• Java 7 has a number of new concurrency toys
• The headline item is Fork / Join
- Similar to Map/Reduce, useful for a certain class of problems
- Fork and join executions are not necessarily threads
• We’ll cover this in the final hour!

32. Java 7 - That’s not all
• Nimbus Look & Feel for Swing
• New helper classes including Objects
- deepEquals() and friends
• JDBC with try-with-resources support
• Better unicode support
- Thanks in part to Tom Christiansen of Perl fame
• More small changes in niche areas

33. New Faces in the OpenJDK

34. What We Didn’t Have Time To Talk About
• Java 8
- Java FX 2.x
• Java EE 6/7
• Java ME
• JDK Enhancement Proposals (JEPs)
• Java Community Process (JCP)
- Java Specification Requests (JSRs)
- Java User Groups (JUGs) and 'Adopt' programs

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