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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<title>reveal.js</title>
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/theme/moon.css">
<!-- Theme used for syntax highlighting of code -->
<link rel="stylesheet" href="lib/css/zenburn.css">
<!-- Printing and PDF exports -->
<script>
var link = document.createElement( 'link' );
link.rel = 'stylesheet';
link.type = 'text/css';
link.href = window.location.search.match( /print-pdf/gi ) ? 'css/print/pdf.css' : 'css/print/paper.css';
document.getElementsByTagName( 'head' )[0].appendChild( link );
</script>
</head>
<body>
<div class="reveal">
<div class="slides">
<section>
<section>
<h2>And Java becomes more functional With Javaslang!</h2>
<img src="assets/img/javaslang-logo.png" class="no-borders">
</section>
<section>
<h2>And Java becomes more functional with <span style="text-decoration:line-through;">Javaslang</span>!</h2>
<div class="img-strike">
<img src="assets/img/javaslang-logo.png" class="no-borders">
</div>
</section>
<section>
<h2>And Java becomes more functional with Vavr.io!</h2>
<img src="assets/img/vavr-logo.png" class="no-borders">
</section>
</section>
<section>
<section data-background-image="./assets/img/lambda.svg" data-background-size="60%">
<h2>Functional Programming</h2>
<h4>What does it mean? </h4>
</section>
<section>
<h2>No more side effects!</h2>
<ul>
<li> Functions are first-class citizens </li>
<li> Immutability </li>
<li> Expressiveness </li>
<li> Safety </li>
</ul>
</section>
<section>
<h2>Referential Transparency</h2>
<div class="">
<pre>
<code class="java">int globalValue = 0;
// No Referential Transparency
int rq(int x) {
globalValue++;
return x + globalValue;
}
//Referential Transparency
int rt(int x) {
return x + 1;
}
</code>
</pre>
</div>
</section>
<section>
<h2>Referential Transparency</h2>
<h3>Other example</h3>
<div class="">
<pre>
<code class="java">// No Referential Transparency
Math.random();
//Referential Transparency
Math.max(5, 42);
</code>
</pre>
</div>
</section>
</section>
<section>
<h2>Java 8 & Functional Programming</h2>
<ul>
<li>Lambda</li>
<li>Stream</li>
<li>Optional</li>
<li>Functional Interface</li>
<li>Function composition</li>
<li>Collections interfaces review</li>
</ul>
</section>
<section data-background-image="./assets/img/frustration.gif">
<h2>There's still stuff missing</h2>
</section>
<section>
<h2>Who I am ?</h2>
<img src="./assets/img/avatar.png" height="300" class="no-borders" style="float: left">
<ul style="margin-top: 30px">
<li>Twitter : <a href="https://www.twitter.com/glours">@glours</a></li>
<li><a href="www.saagie.io">Saagie</a> 'Frozen' Team Leader</li>
<li>Java and Javascript developer</li>
<li>Team member of Devoxx France</li>
</ul>
</section>
<section>
<section>
<h2>So ...</h2>
<img src="./assets/img/vavr-logo.png">
</section>
<section data-background-color="white">
<img src="./assets/img/javaslang-overview.png" class="no-borders">
</section>
</section>
<section>
<section>
<h2>Immutable Collections</h2>
</section>
<section>
<h2>It's already in JDK 8 !</h2>
<h5>Humm....</h5>
<pre><code class="java">public List<Integer> unmodifiableListJdk8() {
List<Integer> jdkList = IntStream.range(0,20)
.boxed()
.collect(Collectors.toList());
return Collections.unmodifiableList(jdkList);
}
@Test
public void should_verify_behaviour_of_jdk_8_unmodifiable_list() throws Exception {
List<Integer> unmodifiableList = this.examples.unmodifiableListJdk8();
unmodifiableList.add(21);
assertThat(unmodifiableList).hasSize(21);
}
</code></pre>
</section>
<section data-background-color="white">
<h2>List, Array, Stream ...</h2>
<img src="./assets/img/collections-seq.png" class="no-borders" alt="" width="1000">
</section>
<section>
<h2>Java 8 example</h2>
<pre><code class="java">java.util.List<User> filterUserWithValidEmail() {
return this.usersJdk8
.stream()
.filter(user -> {
try {
return user.isEmailValid();
} catch (InvalidFormatException e) {
return false;
}
})
.collect(Collectors.toList());
} </code></pre>
</section>
<section>
<h2>With Vavr</h2>
<pre><code class="java">public List<User> filterUserWithValidAddressVavr() {
return this.usersVavr
.filter(user -> Try.of(() -> user
.isAddressValid())
.getOrElse(false));
}
</code></pre>
</section>
<section>
<h2>An other Java 8 example</h2>
<pre><code class="java">public java.util.List<Address> filterInvalidAddressFromRouenJdk8() {
return this.usersJdk8.stream()
.filter(User::isInvalidAddressFromRouen)
.map(User::getAddress)
.collect(Collectors.toList());
}
</code></pre>
</section>
<section>
<h2>And With Vavr</h2>
<pre><code class="java">public List<Address> filterInvalidAddressFromRouenVavr() {
return this.usersVavr
.filter(User::isInvalidAddressFromRouen)
.map(User::getAddress);
}
</code></pre>
</section>
<section>
<h2>Stream consistency</h2>
<p>Java 8</p>
<pre><code class="java">public java.util.stream.Stream<String> mapUserToLowerCaseUserNameWithJdk8Steam() {
java.util.stream.Stream<User> userNameStream = java.util.stream.Stream.of(generateUser(7), generateUser(15));
userNameStream.map(user -> user.getUserName()
.toUpperCase());
return userNameStream
.map(user -> user.getUserName().toLowerCase());
}
java.lang.IllegalStateException: stream has already been operated upon or closed
at java.util.stream.AbstractPipeline.<init>(AbstractPipeline.java:203)
at java.util.stream.ReferencePipeline.<init>(ReferencePipeline.java:94)
at java.util.stream.ReferencePipeline$StatelessOp.<init>(ReferencePipeline.java:618)
at java.util.stream.ReferencePipeline$3.<init>(ReferencePipeline.java:187)
at java.util.stream.ReferencePipeline.map(ReferencePipeline.java:186)</code></pre>
</section>
<section>
<h2>Stream consistency</h2>
<p>Vavr</p>
<pre><code class="java">public Stream<String> mapUserToLowerCaseUserNameWithVavrStream() {
Stream<User> userNameStream = Stream.of(generateUser(7), generateUser(15));
userNameStream.map(user -> user.getUserName()
.toUpperCase());
return userNameStream
.map(user -> user.getUserName().toLowerCase());
}
</code></pre>
</section>
<section data-background-color="white">
<h2>Map, Set ...</h2>
<img src="./assets/img/collections-set-map.png" class="no-borders" width="1000">
</section>
<section>
<h2>Tuple</h2>
<img src="./assets/img/tuple-javadoc.png" class="no-borders">
</section>
<section>
<h2>Java 8 example</h2>
<pre><code class="java">public java.util.Map<String, User> filterMapOfUserWithValidAddressJdk8() {
java.util.Map<String, User> usersMap = this.usersToMapJdk8();
return usersMap.entrySet().stream()
.filter(entry -> {
try {
return entry.getValue().isAddressValid();
} catch (InvalidFormatException e) {
return false;
}
})
.collect(Collectors.toMap((entry -> entry.getKey()), entry -> entry.getValue()));
}</code></pre>
</section>
<section>
<h2>With Vavr</h2>
<pre><code class="java">public Map<String, User> filterMapOfUserWithValidAddressVavr() {
Map<String, User> userMap = this.usersToMap();
return userMap
.filter(tuple -> Try.of(() ->
tuple._2.isAddressValid()).getOrElse(false));
}
</code></pre>
</section>
</section>
<section>
<section>
<h2>Value Types</h2>
<ul>
<li>Option</li>
<li>Try</li>
<li>Either</li>
<li>Validation</li>
<li>(Lazy, Future, Promise, Match)</li>
</ul>
</section>
<section>
<h2>Option</h2>
<h5>1 Interface</h5>
<img src="./assets/img/javaslang-none.png" alt="Javaslang None Object definition" class="no-borders">
<img src="./assets/img/javaslang-some.png" alt="Javaslang Some Object definition" class="no-borders">
</section>
<section>
<h2>Java 8 Optional</h2>
<pre><code class="java">public Optional<Address> optionalOfUserAddress(String userName) {
if( !this.usersJdk8.containsKey(userName)) {
return Optional.empty();
}
return Optional.of(this.usersJdk8.get(userName).getAddress());
}
public Optional<Address> optionalOfNullUsageForUserAddress(String userName) {
return Optional.ofNullable(this.usersJdk8.get(userName))
.map(user -> user.getAddress());
}
</code></pre>
</section>
<section>
<h2>Vavr Option</h2>
<pre><code class="java">public Option<Address> optionOfUserAddress(String userName) {
return this.usersVavr.get(userName)
.map(user -> user.getAddress());
}
/* Because Map.get(key) return an Option in Vavr
Option<V>get(K var1);
*/
</code></pre>
</section>
<section>
<h2>Try</h2>
<h5>May return an exception or a successful result</h5>
<pre><code>public Try tryOfUserAddress(String userName) {
return Try.of(() -> this.usersVavr.get(userName)
.get().getAddressIfValid());
}</code></pre>
</section>
<section>
<h2>Either</h2>
<h5>Represents a value of 2 possible types</h5>
<h5>Either is either Right or Left</h5>
<h5>by convention Right refers to the nominal case</h5>
</section>
<section>
<h2>Either Example</h2>
<pre><code> public Either<String, User> eitherOfUser(String userName) {
return this.usersVavr.get(userName)
.toRight("Not Found");
}</code></pre>
</section>
<section>
<h2>Validation</h2>
<h5>Errors accumulation</h5>
<h5>Processes all validations, no circuit breaking when an error is found</h5>
</section>
<section>
<h2>Example available on github</h2>
<a href="https://github.com/glours/vavr-examples">GitHub: https://goo.gl/BHcYRJ</a>
</section>
</section>
<section>
<section>
<h2>Functions</h2>
<h5>What about the first-class citizens ?</h5>
</section>
<section>
<h2>Java 8 comes with Function and BiFunction</h2>
<h2>Vavr provides functional interfaces up to 8 parameters</h2>
</section>
<section>
<blockquote>In fact Vavr functional interfaces are Java 8 functional interfaces on steroids</blockquote>
<a href="http://www.vavr.io/vavr-docs/#_functions">Vavr documentation</a>
</section>
<section>
<h2>Composition</h2>
<h5>Application of one function as the result of another to produce a new one</h5>
</section>
<section>
<h2>Composition example</h2>
<pre><code class="java">private Function1<Option<User>, Option<String>> lastName
= user -> user.map(exist -> exist.getLastName());
private Function1<Option<String>, Option<String>> toUpperCase
= value -> value.map(string -> string.toUpperCase());
private Function1<Option<User>, Option<String>> lastNameInUpperCase
= lastName.andThen(toUpperCase);
public String userLastNameToUpperCase(String userName) {
return lastNameInUpperCase
.apply(usersJavaslang.get(userName))
.getOrElse("User Not Found");
}
</code></pre>
</section>
<section>
<h2>Lifting</h2>
<h5>Turning a side effect function to a total function</h5>
</section>
<section>
<h2>Lifting example</h2>
<pre><code class="java">private Function1<Option<User>, Address> getAddressWithSideEffect
= user -< user.get().getAddress();
private Function1<Option<User>, Option<Address>> safeGetAddress
= Function1.lift(getAddressWithSideEffect);
public Address sideEffectGetAddress(String userName) {
return getAddressWithSideEffect
.apply(usersJavaslang.get(userName));
}
public Option<Address> safeGetAddress(String userName) {
return safeGetAddress
.apply(this.usersVavr.get(userName));
}
</code></pre>
</section>
<section>
<h2>Partial Application</h2>
<h5>Deriving a new function from an existing one by fixing some parameters</h5>
</section>
<section>
<h2>Partial Application example</h2>
<pre><code class="java">private Function4 <Integer,Integer,Integer,Integer,Integer> sum
= (a, b, c, d ) -> a + b + c + d;
private Function1<Integer, Integer> partialApplicationFunc
= sum.apply(1,2,3);
public int partialApplication(int val) {
return partialApplicationFunc.apply(val);
}
</code></pre>
</section>
<section>
<h2>Currying</h2>
<h5>Deriving a new function from an existing by fixing 1 parameter and returning a new function with arity of 1</h5>
</section>
<section>
<h2>Currying example</h2>
<pre><code class="java">private Function1<Integer, Function1<Integer, Function1<Integer, Integer>>> curriedFunc
= sum.curried().apply(5);
public int currying(int val1, int val2, int val3) {
return curriedFunc.apply(val1).apply(val2).apply(val3);
}
</code></pre>
</section>
<section>
<h2>Memoization</h2>
<h5>Kind of cache system</h5>
<h5>A function is executed only once and then returns the result from the cache</h5>
</section>
<section>
<h2>Memoization example</h2>
<pre><code class="java">private Function0>Double< memoizedRandom = Function0.of(Math::random).memoized();
public double memoize() {
return memoizedRandom.apply();
}
@Test
public void should_use_memoization_to_add() throws Exception {
double firstCall = this.examples.memoize();
assertThat(List.range(0, 20)
.map(val -> this.examples.memoize()))
.allMatch(val -> val == firstCall);
}
</code></pre>
</section>
</section>
<section>
<section>
<h2>Pattern Matching and Property checking</h2>
</section>
<section>
<h2>Pattern Matching, the Vavr way</h2>
<ul>
<li>$() - wildcard pattern</li>
<li>$(value) - equals pattern</li>
<lig>$(predicate) - conditional pattern</lig>
</ul>
</section>
<section>
<h2>Syntactic Sugar</h2>
<ul>
<li>Predicate <pre><code>Case(is(1), "one")</code></pre></li>
<li>Multiple conditions <pre><code>Case(isIn("-h", "--help"), ...)</code></pre></li>
<lig>User-Defined Patterns, Guards ...</lig>
</ul>
</section>
<section>
<h2>Pattern Matching example</h2>
<pre><code class="java">Function0<Option<String>> usageDocumentation = () -> Option.of("usage: JavaslangDemo [options] \n") ;
Function1<Option<String>, Option<String>> versionDocumentation = previous -> previous.map(prev -> prev + "-v, --version : Display version Information");
Function0<Option<String>> helpDocumentation = usageDocumentation.andThen(versionDocumentation);
Function2<Option<String>, Option<String>, Option<String>> invalidCommand = (previous, arg) -> previous.map(prev -> "Unable to parse command line option : " + arg.getOrElse("") +"\n" + prev);
public static void main( String[] args )
{
Option<String> arg = Array.of(args).headOption();
String commandDescription = API.Match(arg.getOrElse("")).of(
Case(isIn("-h", "--help"), helpDocumentation.apply()),
Case(isIn("-v", "--vesion"), versionDocumentation.apply(Option.none()) ),
Case($(), invalidCommand.apply(helpDocumentation.apply(), arg))
).getOrElse("Error when parsing argument");
System.out.println(commandDescription);
}
</code></pre>
</section>
<section>
<h2>Another example</h2>
<pre><code class="java">public List<Either<Address, Address>> patternMatchingList() {
List<User> users = this.usersVavr.map(tuple -> tuple._2).toList();
return users.map(user ->
Match(validateUser(Option.of(user))).of(
Case(Valid($()), validUser -> Either.right(validUser.getAddress())),
Case(Invalid($()), errorList -> Either.left(user.getAddress()))
));
}
</code></pre>
</section>
<section>
<h2>Property Checking</h2>
</section>
<section>
<h2>Property Checking example</h2>
<pre><code class="java">@Test
public void should_l33t_string() throws Exception {
Arbitrary<String> leetCharEto3 = Arbitrary.string(Gen.frequency(
Tuple.of(1, Gen.choose('A','Z')),
Tuple.of(1, Gen.choose('a','z'))
))
.filter(s -> s.length() > 10)
.filter(s -> s.matches("\\w*[eE]+\\w*"));
Function1<String, String> transformETo3 =
s -> s.replaceAll("[eE]", "3");
CheckedFunction1<String, Boolean> checkTransformETo3 =
s -> transformETo3.apply(s)
.matches("\\w*[^eE]+\\w*")
&& transformETo3.apply(s).contains("3");
Property.def("Each e character must be replace by a 3")
.forAll(leetCharEto3)
.suchThat(checkTransformETo3)
.check()
.assertIsSatisfied();
}
</code></pre>
</section>
</section>
<section>
<h2>Vavr Modules</h2>
<img src="./assets/img/vavr-modules.png" alt="" class="no-borders">
</section>
<section>
<h2>Vavr Links</h2>
<p><a href="https://www.vavr.io/vavr-docs/">Documentation: https://goo.gl/dMKKjN</a></p>
<p><a href="http://www.javadoc.io/doc/io.javaslang/javaslang/2.0.6">Javadoc: https://goo.gl/PHQ81g</a></p>
<p><a href="https://github.com/vavr-io/vavr">Source code : https://goo.gl/p3ivLM</a></p>
</section>
<section data-background-image="./assets/img/thank_you.gif">
<h1>Thank You</h1>
</section>
<section data-background-image="./assets/img/mandatory.gif">
<h1>Questions ?</h1>
<p><a href="https://github.com/glours/vavr-examples">source code: https://goo.gl/BHcYRJ </a></p>
</section>
</div>
</div>
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backgroundTransition: 'fade', // none/fade/slide/convex/concave/zoom
viewDistance: 3,
// More info https://github.com/hakimel/reveal.js#dependencies
dependencies: [
{ src: 'plugin/markdown/marked.js' },
{ src: 'plugin/markdown/markdown.js' },
{ src: 'plugin/notes/notes.js', async: true },
{ src: 'plugin/highlight/highlight.js', async: true, callback: function() { hljs.initHighlightingOnLoad(); } }
]
});
</script>
</body>
</html>