1.
Eclipse Collections, Java Streams & Vavr -
What's in them for
Functional Programming
Naresha K
Independent Consultant
@naresha_k
https://blog.nareshak.com/

2.
Java Streams

3.
https://www.eclipse.org/collections/

4.
A Taste of APIs

5.
public static List<Developer>
getSampleListOfDevelopers() {
List<Developer> developers = new
ArrayList<>();
developers.add(new Developer("Raj", 30,
Arrays.asList("Java", "JavaScript")));
developers.add(new Developer("Meena", 24,
Arrays.asList("Java", "Groovy", "Scala")));
developers.add(new Developer("Mark", 28,
Arrays.asList("Java", "JavaScript", "Groovy")));
return developers;
}

6.
List<Developer> developerYoungerThan30Years = developers
.stream()
.filter(developer -> developer.getAge() < 30)
.collect(Collectors.toList());
System.out.println(developerYoungerThan30Years);

7.
String namesOfDevelopersSeparatedByComma = developers
.stream()
.map(developer -> developer.getName())
.collect(Collectors.joining(", "));
System.out.println(namesOfDevelopersSeparatedByComma);

8.
Set<String> languagesKnown = developers
.stream()
.map(developer -> developer.getLanguages())
.flatMap(List::stream)
.collect(Collectors.toSet());
System.out.println(languagesKnown);

9.
MutableList<Developer> developers = Lists.mutable.of(
new Developer("Raj", 30, Arrays.asList("Java", "JavaScript")),
new Developer("Meena", 24, Arrays.asList("Java", "Groovy", "Scala")),
new Developer("Mark", 28, Arrays.asList("Java", "JavaScript", "Groovy"))
);

10.
MutableList<Developer> developersYoungerThan30 =
developers
.select(developer -> developer.getAge() < 30);
System.out.println("Age < 30: " + developersYoungerThan30);
System.out.println("All Devs: " + developers);
MutableList<Developer> developersYoungerThan30Alternate =
developers
.reject(developer -> developer.getAge() >= 30);
System.out.println("Age < 30: " + developersYoungerThan30Alternate);

11.
String namesOfDevelopers = developers
.collect(developer -> developer.getName())
.makeString(", ");
System.out.println("Names: " + namesOfDevelopers);

12.
MutableList<String> languages = developers
.flatCollect(developer ->
Lists.mutable.ofAll(developer.getLanguages()))
.distinct();
System.out.println(languages);

13.
List<Developer> developers = List.of(
new Developer("Raj", 30, Arrays.asList("Java", "JavaScript")),
new Developer("Meena", 24, Arrays.asList("Java", "Groovy", "Scala")),
new Developer("Mark", 28, Arrays.asList("Java", "JavaScript", "Groovy")));

14.
List<Developer> developersYoungerThan30 = developers
.filter(developer -> developer.getAge() < 30);
System.out.println(developersYoungerThan30);

15.
String namesOfDevelopers = developers
.map(developer -> developer.getName())
.intersperse(", ")
.reduce((v1, v2) -> v1 + v2);
System.out.println(namesOfDevelopers);

16.
List<String> languagesKnown = developers
.map(developer -> developer.getLanguages())
.flatMap(Function.identity())
.distinct();
System.out.println(languagesKnown);

17.
Mutable vs Immutable

18.
Mutable vs Immutable
Java Streams
Implicit (Effectively Final)
Collections - mostly mutable
Eclipse Collections Explicit / Different APIs
Vavr Immutable only

19.
Eager vs Lazy

20.
Eager vs Lazy
Java Streams Lazy
Eclipse Collections Explicit / Different APIs
Vavr Explicit / Different APIs

21.
Serial vs Parallel

22.
Serial vs Parallel
Java Streams
Serial (default)
Easy to switch to Parallel
Eclipse Collections
Serial (default)
Limited support for Parallel
Vavr No support for Parallel

23.
Streams Gotchas

24.
Error Handling

25.
Java Collections Inter-op

26.
Fluency of API

27.
https://github.com/eclipse/eclipse-collections/blob/master/docs/guide.md#-basic-collection-types

28.
Container Factory
List Lists
Set Sets, HashingStrategySets
Bag Bags
Stack Stacks
SortedBag SortedBags
SortedSet SortedSets
Map Maps, HashingStrategyMaps
SortedMap SortedMaps
BiMap BiMaps
Multimap Multimaps
https://github.com/eclipse/eclipse-collections/blob/master/docs/guide.md#-creating-mutable-collections

29.
References
• https://www.infoq.com/presentations/java8-functional-programming-vavr/
• https://github.com/naresha/fnconf2019