La idea de la charla es dar un comparación entre los diversos features de ambos lenguajes como: * Lambdas/Closures * Method references * Default Methods / Traits * Soporte de APIs de Java 8 en Groovy

1. Groovy & Java 8
A very simple comparison
@ JaverosMX, Mexico City
30/Marzo/2015Domingo Suárez Torres (@domix)

2. Agenda
• Background
• A little bit about Groovy
• Why is important to upgrade to Java 8
• Comparison
• Very small :’(

3. Groovy, just a little
• Optionally typed & dynamic language for the
JVM
• Static-typing and static compilation capabilities
• Scripting capabilities, Domain-Specific
Language authoring, runtime and compile-time
meta-programming and functional programming

4. Seamlessly and transparently
integrates and interoperates with
Java and any third-party libraries

6. Java 8 matters
• Java 7 EOL. April 2015
• Java 6 < go figure.
• “Brand new” techniques, patterns, paradigms. Built in the language.
• Very soon libraries and frameworks will adopt those improvements.
• Enhancements
• Nashorn
• Invoke-dynamic
• Java 8 arrived late to the party. Better late than never.

7. Java 8 features
• New Syntax
• Stream API
• Profiles
• JavaFX
• Date/Time API
• Nashorn
• Pack200
• JDBC
• Concurrency
• JAXP
• Hotspot
• Java Mission Control

8. Java 8 syntax
• Lambda expressions
• Method references
• static & default methods in interfaces
• Repeating annotations
• Annotation on types
• Improved type inference
• Method parameter reflection

10. Comparison

11. Feature similarities
• Java 8
• Lambda expressions
• Default methods
• Optional types
• Stream API
• Method references
• Groovy
• Closures
• Traits
• Truth & null handling
• GDK Collections
• Method closures

12. Code as data
• Interfaces with one method (functional interface)
• Single Abstract Method interfaces (SAM Interfaces)
• Inner classes are annoying due verbosity.
• Java 8 Lambda Expressions, Groovy Closures.
• JVM functions became almost first-class
citizens.

13. Java 8 Lambdas

15. Lambda expressions

17. Groovy Closures
• Since 2003.
• Is an open, anonymous, block of code that can take
arguments.
• Return a value and be assigned to a variable.
• A closure may reference variables declared in its
surrounding scope.
• Can also contain free variables which are defined outside
of its surrounding scope. In opposition to the formal
definition of a closure.

18. Closures in action

19. GDK (Groovy Dev Kit)

20. Closures behind scenes
• Groovy creates an inner anonymous class
• groovy.lang.Closure implements
• Cloneable
• Runnable
• GroovyCallable
• java.util.concurrent.Callable
• Serializable

21. Java 8 with Groovy

22. Java 8
Default methods

23. Default methods
• Non-abstract method implementations to
interfaces by utilizing the default keyword
• Also know as Extension Methods

24. Default methods

25. Default methods
• Can be static methods
• We can use them to implement multiple
inheritance
• Naming conflict¡

27. Groovy Traits

28. Traits
• The same idea as default methods in Java
• Interface with method bodies
• Can be stateful
• Multiple inheritance

31. Stream API

32. java.util.Stream
• Represents a sequence of elements on which one or
more operations can be performed.
• Stream operations are either intermediate or terminal.
• While terminal operations return a result of a certain type,
intermediate operations return the stream itself so you
can chain multiple method calls in a row.
• Streams are created on a source (Collection)
• Stream operations can either be executed sequential or
parallel.

33. Streams usage

34. Streams with
method references

35. Map-Reduce

36. GDK Collections

37. Groovy GDK
• Groovy add lots of enhancements into the
standard JDK
• Groovy “injects” additional methods on the
standard Java libraries
• GDK adds syntactic sugar to Java APIs for
better and easier usage.

38. Using GDK facilities

39. GDK and Java 8
• Some GDK facilities will be deprecated in favor
of Stream
• Stream is more efficient and performant
• Groovy will focus in better integration with Java 8
enhancements

40. Java 8 Optionals

41. java.util.Optional<T>
• NPE is awkward.
• A optional is a container object which may or
may not contain a non-null value.
• Additional methods that depend on the
presence or absence of a contained value are
provided, such as orElse() (return a default value
if value not present) and ifPresent() (execute a
block of code if the value is present).

42. Optional usage

43. Stream/Optional
real life example

44. Groovy Truth

45. Groovy Truth
• Everything that’s null, empty, zero-sized, equal to
zero is false. Otherwise is true
• Groovy Truth is quite simple: just implement a
custom asBoolean() method.

46. Null handling in Groovy

47. What to do?
• IMO, Java 8 is a great release
• Groovy is a madure alternative language for the
JVM
• My recommendation is to use both languages

48. Java 8 highlights
• Lambdas
• Stream API
• Nashorn. Avatar project

49. Groovy Highlights
• Traits
• Metaprogramming
• AST Transformations
• DSL authoring
• Android support
• @TypeChecked @CompileStatic

50. Contact
• @domix
• domingo.suarez@gmail.com
• #JaverosMX

51. Picture credits
• https://www.flickr.com/photos/eneas/3108310839/
• https://www.flickr.com/photos/eneas/6395912803/
• https://www.flickr.com/photos/80651083@N00/5641290457/
• https://www.flickr.com/photos/annuar_martinez/3282050044/
• https://www.flickr.com/photos/luismontemayor/2550701324/
• https://www.flickr.com/photos/guseher/2393646953/
• https://www.flickr.com/photos/annuar_martinez/2342099774/
• https://www.flickr.com/photos/luismontemayor/4306210583/
• https://www.flickr.com/photos/lastingimages/12262034856/
• https://www.flickr.com/photos/atejada/14169147706/
• https://www.flickr.com/photos/luismontemayor/3018556662/
• https://www.flickr.com/photos/eneas/2290156408/
• https://www.flickr.com/photos/122274109@N03/16154663524/
• https://www.flickr.com/photos/krynowekeine/2755263171/
• https://www.flickr.com/photos/nino_ary/2901716788/
• https://www.flickr.com/photos/eneas/5279761/
• https://www.flickr.com/photos/lastingimages/12373124983/
• https://www.flickr.com/photos/rmgg-photos/8503188042/
• https://www.flickr.com/photos/luajr/15127961825/
• https://www.flickr.com/photos/gtercero/8740734623/
• https://www.flickr.com/photos/egmzcp15/5237066174/
• https://www.flickr.com/photos/rouleau/109405487/
• https://www.flickr.com/photos/xavier333/2257501542/
• https://www.flickr.com/photos/pvcg/3087911579/
• https://www.flickr.com/photos/notocajrs/12785034584/
• https://www.flickr.com/photos/nahual_neo/8005123271/
• https://www.flickr.com/photos/chicotown/3189442699/
• https://www.flickr.com/photos/kootenayhulio/5497898774/
• https://www.flickr.com/photos/maybemaq/16579363326/
• https://www.flickr.com/photos/luajr/15484454837/

52. Picture credits
• https://www.flickr.com/photos/nahual_neo/4290121443/
• https://www.flickr.com/photos/70120970@N08/8493760801/
• https://www.flickr.com/photos/gustavothomastheatre/15823470423/
• https://www.flickr.com/photos/graficris_lgs/15543907818/
• https://www.flickr.com/photos/gustavothomastheatre/15708898754/
• https://www.flickr.com/photos/john_colby/8430729849/
• https://www.flickr.com/photos/egmzcp15/4144937818/
• https://www.flickr.com/photos/10066932@N03/2552609658/
• https://www.flickr.com/photos/bdebaca/2987372965/
• https://www.flickr.com/photos/beco/23806123