The document presents a comparison between Groovy and Java 8, highlighting the features and improvements introduced in Java 8, such as lambda expressions, stream API, and optional types. It emphasizes Groovy's capabilities, such as dynamic typing, closures, and traits, which enhance Java's static features. The conclusion recommends utilizing both languages for different advantages in JVM development.

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/
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• https://www.flickr.com/photos/luajr/15127961825/
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• 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