An introduction to ReactiveX library, one on the major implementations for reactive programming concepts.

2. ReactiveX
The best of functional programming and design
patterns !

3. Agenda
● Functional Programming (Java 8)
○ Getting Started
○ Examples
● Observer Pattern
○ Introduction
○ Real life example
○ UML
● ReactiveX
○ Introduction
○ Getting Started
○ Example
○ Operators

4. Getting Started with Functional Programming
(Java 8)

5. Functional Programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

6. Functional Programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

7. Introduction
● It is a declarative programming paradigm, which means programming is
done with expressions.
● Functional code, the output value of a function depends only on the
arguments that are input to the function.

8. Functional Programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

9. Lambda Expressions & Streams

10. Check Prime Numbers

11. Stream From Collection

12. Functional Programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

13. Filter Stream

14. Functional Programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

15. Sort Stream
- The ordering of stringCollection is untouched.

16. Functional programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

17. Map Stream

18. Functional programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

19. Match Stream

20. Match Stream

21. Match Stream

22. Functional programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

23. Count

24. Functional programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

25. Optional in Java 8

26. Functional programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

27. Reduce Stream

28. Functional programming
● Introduction
● Streams and lambda expressions
● Stream operations
⚪ Filter Stream
⚪ Sort Stream
⚪ Map Stream
⚪ Match Stream
⚪ Stream count
● Optionals
● Reduce Stream
● Parallel vs Sequential streams

29. Parallel vs Sequential Streams
Sequential stream
Parallel stream

30. Agenda
● Functional Programming (java 8)
○ Getting Started
○ Examples
● Observer Pattern
○ Introduction
○ Real life example
○ UML
● ReactiveX
○ Introduction
○ Getting Started
○ Example
○ Operators

31. Observer pattern

32. Introduction
● Defines a “one-to-many” dependency between objects so that when one
object changes state, all its dependents are notified and updated.
● Subject: the object which will frequently change its state and upon
which other objects depend.
● Observer: the object which depends on a subject and updates according
to its subject’s state.

33. Real Life Example

34. UML

35. Agenda
● Functional Programming (java 8)
○ Getting Started
○ Examples
● Observer Pattern
○ Introduction
○ Real life example
○ UML
● ReactiveX
○ Introduction
○ Getting Started
○ Example
○ Operators

36. ReactiveX
ReactiveX is a combination of the best ideas from
the Observer pattern, the Iterator pattern, and functional programming

37. Introduction
● Reactive programming is a programming paradigm
oriented around data flows and propagation of change.
● Let:
a = b + c
what about if b or c has been changed?!

38. Introduction
● Functional Reactive programming (FRP) is a style of
programming based on two keys ideas: continuous
time-varying behaviors, and event based reactively.
● Popularized by Erik Meijer when he created the Rx
library for .Net while at Microsoft.

39. Reactive Programming
Reactive programming is programming with asynchronous data streams.

40. What Are Reactive Extensions?
● It’s a library that allows you to use FRP at many
programming languages.
● Allows you to represent asynchronous data streams
with “Observables”.
● And Parametrize the concurrency in those
asynchronous data streams using “Schedulers”

41. Rx Family
● C#: Rx.NET
● Javascript: RxJS
● RxJava (Java, Scala, Groovy, Clojure, Kotlin).
● Ruby: Rx.rb
● Python: RxPY
● More at http://reactivex.io/

42. Why Functional Reactive Programming?
● Writing concurrent programs correctly is difficult.
● You can transform & compose asynchronous operations.
● High-level abstraction.
● Standard error handling.

43. Push vs Pull

44. Observables and Observer
● In ReactiveX an Observer subscribes to an Observable.
● Then That Observer reacts to whatever item or sequence of items the
Observable emits.
● This patterns facilitate concurrent operations because it does not need
to block while waiting for the observable.

45. Observer onNext, onCompleted, onError
An Observer implements a subset of the following methods:
● onNext: We call this method whenever the Observable emits an item.
● onError: Call this method to indicate the the observable has failed and
will not make further calls to onNext or onCompleted.
● onCompleted: Call this method after you have called onNext for the final
time and if we have not encountered any errors.

46. The “Subscribe” method

47. RxJava
● It’s a JVM implementation of Reactive Extensions.
● Started at Netflix but now Open Sourced.
● Supports Java 6+ & Android 2.3+.
● Java 8 lambda support.

48. Creating an Observable

49. Creating an Observable

50. Creating an Observable

51. Transforming Observables

52. Filtering Observables

53. Filtering Observables
● first()
● distinct()
● take()
● skip()
● elementAt()
● sample()
● more …
● More at
https://github.com/ReactiveX/RxJava/wiki/Filtering-Observables

54. Aggregate Operators

55. Combining Observables

56. Combining Observables

57. Thanks !