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Java 8Level Up with new features!

Socal Code Camp 201514 Nov, Los Angeles

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Java 8Level Up with new features!

Image: http://blog.takipi.com/

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Who am I?

@cganoo@cganoo

Trademarks and pictures belong to respective copyright owners

@caganoo

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Agenda

Introduction

Default Methods

Lambdas

Streams

CompletableFuture

Demo

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Intro

Popularity Rank on GitHub

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https://redmonk.com/sogrady/2015/07/01/language-rankings-6-15/

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Intro

https://dzone.com/articles/java-version-statistics-2015http://www.oracle.com/technetwork/java/eol-135779.html

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Default Methods

Interview Question:

What is an interface in java?

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Default Methods

Interfaces can now declare methods with implementation: Static methods Default Methods

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Default Methods

List<Integer> numbers = Arrays.asList(3, 5, 1);

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Default Methods

List<Integer> numbers = Arrays.asList(3, 5, 1);

Collections.sort(numbers);

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Default Methods

List<Integer> numbers = Arrays.asList(3, 5, 1);

Collections.sort(numbers);

Collections.sort(numbers, myComparator);

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Default Methods

List<Integer> numbers = Arrays.asList(3, 5, 1);

numbers.sort(Comparator.naturalOrder());

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Default Methods

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Default Methodspublic class Dog implements Bark {

// No overridden method}

public interface Bark { default String bark() { return "Woof Woof!"; }}

public static void main(String[] args) { Dog dog = new Dog(); dog.bark(); // Woof Woof!}

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Default Methods

Interview Question:

What's the difference between Abstract classes and Interfaces?

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Default Methods

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Default Methods

3 Resolution Rules:

Classes always win Then, sub-interfaces win Then, the inheriting class inheriting has to

explicitly select

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Lambdas

Image: http://blog.takipi.com/

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Lambdas

Concise way to express Behavior Parametrization

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LambdasList<Student> filterByGrade(students, grade) {

List<Student> result = new ArrayList<>();

for (Student student : students) {if

( student.getGrade().equals(grade) ) {result.add(student);

}}return result;

}

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Lambdas

List<Student> gradeAStudents = filterByGrade(students, "A");

List<Student> gradeBStudents = filterByGrade(students, "B");

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LambdasList<Student> filterByAge(students, age) {

List<Student> result = new ArrayList<>();

for (Student student : students) {if ( student.getAge() > age ) {

result.add(student);}

}return result;

}

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Lambdas

List<Student> oldStudents = filterByAge(students, 30);

List<Student> youngStudents = filterByAge(students, 20);

Value Parameterization!

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Lambdaspublic interface Predicate<T> {

boolean test(T t);}

List<T> filter(List<T> list, Predicate<T> p) {

List<T> result = new ArrayList<>();for(T e: list) {

if(p.test(e)){ result.add(e); }}return result;

}

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Lambdas

filter( students,

(Student s) -> "A".equals(s.getGrade()));

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LambdasComparator<Student> c = new Comparator<Student>() {

public int compare(Student a1, Student a2) {

return a1.getAge().compareTo(a2.getAge());

}};

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LambdasComparator<Student> c = new Comparator<Student>() {

public int compare(Student a1, Student a2) {

return a1.getAge().compareTo(a2.getAge());

}};

Comparator<Student> c = (Student a1, Student a2) -> a1.getGrade().compareTo(a2.getGrade());

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Lambdas

So where can you use lambdas?

In the context of a functional interface

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Lambdas

A functional interface is an interface that specifies exactly one abstractmethod

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Lambdas@FunctionalInterfacepublic interface Runnable {

public abstract void run();}

@FunctionalInterfacepublic interface Callable<V> {

V call() throws Exception;}

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Lambdas

Thread thread1 = new Thread(new Runnable() { @Override public void run(){ doSomething(); }}); thread1.start();

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Lambdas

Thread thread1 = new Thread(new Runnable() { @Override public void run(){ doSomething(); }}); thread1.start();

new Thread(() -> doSomething()).start();

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Lambdas@FunctionalInterfacepublic interface Predicate<T> {

boolean test(T t);}

@FunctionalInterfacepublic interface Function<T, R> {

R apply(T t);}

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Lambdas

Method References:

items.forEach((x) -> System.out.print(x));

items.forEach(System.out::print);

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Lambdas

Image taken from the book ‘Java 8 in Action’ by Urma, Fusco and Mycroft

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Streams

Image: http://www.123rf.com/photo_5391089_blue-tsunami-wave-two.html

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Streams

Stream is a sequence of elements from a source that supports data processing operations

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StreamsMotivation: Collections is the most heavily used API in

Java

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StreamsMotivation: Collections is the most heavily used API in

Java Lacks declarative syntax

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StreamsMotivation: Collections is the most heavily used API in

Java Lacks declarative syntax Lacks easy parallelization API

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Streams

Stream is a sequence of elements from a source that supports data processing operations:

Fancy iterators that let you manipulate collections of data in a declarative, composable and transparently parallel way

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Streams

Streams are Collections on steroids!

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Streams

List<String> someStudentNames =students.stream()

.filter(s -> s.getAge() > 20)

.sorted(comparing(Student::getGrade)).map(Student::getName).collect(toList());

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Streams

List<Student> someStudents =students.stream()

.filter(s -> s.getAge() > 20)

.sorted(comparing(Student::getGrade)).map(Student::getName).collect(toList());Get a list of the names of all students, sorted by their

grades and who are above 20 years of age

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Streams

List<Student> someStudents =students.parallelStream()

.filter(s -> s.getAge() > 20)

.sorted(comparing(Student::getGrade)).map(Student::getName).collect(toList());Get a list of the names of all students, sorted by their

grades and who are above 20 years of age

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StreamsIntermediate Operations: Return Stream<X>

filter Predicate<T> T -> booleanmap Function<T, R> T -> Rsorted Comparator<T> (T, T) -> intdistinct

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StreamsTerminal Operations:

forEach Consumer<T> T -> voidcount Returns a longcollect Collector<T, A, R> reduce T identity, BinaryOperator<T>

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Streams

Generating Streams:

Stream.of("Code", "Camp")

Arrays.stream(new int[] {1, 2})

Files.lines() (Java NIO)

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Streams

Generating Infinite Streams:

Stream.iterate(0, n -> n + 2)

Stream.generate(Math::random)

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CF

Interview Question:

What's the difference between Concurrency and Parallelism?

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CF

http://joearms.github.io/2013/04/05/concurrent-and-parallel-programming.html

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CF

Interview Question:

What's a Future in Java?

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CF

Future models an asynchronous computation and provides a reference to its result that will be available when the computation itself is completed

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CF

Future<Double> future = executor.submit(

() -> doSomething());doSomethingElse();

try {Double result =

future.get(1, TimeUnit.SECONDS);} catch (TimeoutException e) {...}

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CFpublic Future<Double> getPrice(String product) { CF<Double> f = new CF<>(); new Thread(() -> { try { double price = price(product); f.complete(price); } catch (Exception ex) { f.completeExceptionally(ex); } }).start(); return f;}

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CF

public Future<Double> getPrice (String product) { return CF.supplyAsync(() -> price(product))

.exceptionally(() -> 0.0);}

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Question

Parallel Streams vs CompletableFutures

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CF

Which one to prefer?

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CFPattern 1: Async Sequencing

thenAccept*Run a function when complete

thenApply*Convert the result using a function when complete

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CFPattern 2: Async Join

thenAcceptBoth* Run a function when both futures are done

thenCombine* Convert the result of 2 futures into a new thing when both are done

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CF

CF<String> user = CF.supplyAsync(() ->

"John");CF<String> id =

CF.supplyAsync( () -> "1");

user.thenCombineAsync(id, (u, i) -> u +

i).thenAccept(System.out::println);

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References

Java 8 in Action: https://www.manning.com/books/java-8-in-action

@Winterberg: http://winterbe.com/posts/2014/03/16/java-8-tutorial/

IntelliJ for Java Projects

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Demo

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Demo

Demo 1:• Run code to periodically fetch tweets from Twitter• Store the fetched tweets somewhere

Tech Stack used:• AWS Lambda to create scheduled function• AWS S3 to store fetched tweets• Twitter Streaming Endpoint to fetch tweets

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Demo

Demo 2:• Index the stored tweets into an ElasticSearch cluster• Explore and visualize patterns using Kibana Dashboards

Tech Stack used:• AWS Lambda to create a function reacting to S3 events• AWS ElasticSearch Service • Kibana 4

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Demo

C03E https://github.com/cganoo/codecamptweetfetcher https://github.com/cganoo/codecamptweetsearcher

The next few slides show screenshots from the demo

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Text Search in ES

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Summary metrics in ES

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Custom Dashboard in ES

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AWS Cloudwatch Metrics

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AWS Lambda Cloudwatch Logs

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Questions?