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Java Users Group

of

Greater Louisville

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Functional Java

Deven Phillips

Senior Software Engineer

Sungard Availability Services

juggl.us

@JUGGLou

+JugglUs

Functional Java

What does it mean to be "functional"?

f(x) = x \times 2

f (x) = x \times 2

Functional Java

Properties of functions

Idempotence

f(x) = x \times 2

f (x) = x \times 2

Functional Java

Properties of functions

Composable

f(x, y) = x \times y

f (x, y) = x \times y

g(x) = f(x, 5)

g (x) = f (x, 5)

g(10) = 50

g (10) = 50

Functional Java

Those are the MAIN tenets of Functions

What about everything else everyone is touting as "functional programming"?

Functional Java

How does Java implement these concepts?

Lambda Expressions

Concurrent Data Structures

Message Passing

Actors

"final" variables

Functional Java

Lambda ( ) Expressions

\lambda

λ

Functional Java

Concurrent Data Structures

java.util.concurrent.*

ConcurrentHashMap

Atomic<Numeric>

(Completable)Future

<Numeric>Accumulator

Functional Java

Streams

java.util.Collection

Collection.stream()

List.stream()

Map.stream()

Queue.stream()