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<!DOCTYPE html>
<html lang="es">
<head>
<meta charset="utf-8"/>
<title>Java 8 vs Java</title>
<meta name="author" content="(Ashida)"/>
<style type="text/css">
.underline { text-decoration: underline; }
</style>
<link rel="stylesheet" href="file:////home/ashida/git/reveal.js/css/reveal.css"/>
<link rel="stylesheet" href="file:////home/ashida/git/reveal.js/css/theme/league.css" id="theme"/>
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<meta name="description" content="EmacsFTW.">
</head>
<body>
<div class="reveal">
<div class="slides">
<section id="sec-title-slide"><h1>Java 8 vs Java</h1><h2>Ashida<h2><h3><a href="mailto:[email protected]">[email protected]</a><h3>
</section>
<section>
<section id="slide-orgfb741da">
<h2 id="orgfb741da">Java 8?</h2>
<div class="outline-text-2" id="text-orgfb741da">
</div></section>
<section id="slide-org6aeb811">
<h3 id="org6aeb811">Introducción, por qué Java 8 ?</h3>
<ul>
<li>Abstración!</li>
<li>Código menos ofuscado</li>
<li>Mucho más fácil de leer</li>
<li>Olvidaos de los bucles!</li>
<li>Flexibilidad</li>
<li>El código se basa en la manipulación del dato, facilitemos eso!</li>
<li>Más óptimo</li>
</ul>
</section>
<section id="slide-org9f63fc2">
<h3 id="org9f63fc2">Ahora empecemos…</h3>
<ul>
<li>Lambdas</li>
<li>Streams</li>
<li><p>
Optionals
</p></li>
</ul>
<div class="figure">
<p><img src="./etoqueeh.jpg" alt="etoqueeh.jpg" />
</p>
</div>
</section>
</section>
<section>
<section id="slide-org736e59e">
<h2 id="org736e59e">lambdas?</h2>
<div class="outline-text-2" id="text-org736e59e">
</div></section>
<section id="slide-org7fdf570">
<h3 id="org7fdf570">Que son?</h3>
<p>
Funciones sin nombre, anonimas, lambda functions.
</p>
<div class="figure">
<p><img src="./lambda.jpg" alt="lambda.jpg" />
</p>
</div>
</section>
<section id="slide-org0d222d9">
<h3 id="org0d222d9">but… why?</h3>
<p>
Antes de java 8:
</p>
<ul>
<li>Crear objeto con el código a ejecutar</li>
<li>Pasar el objeto</li>
<li>Usar algún tipo de diseño que permita eso</li>
</ul>
<p>
Después de java 8:
</p>
<ul>
<li>Crear bloque de código</li>
<li>Pasarlo como argumento</li>
</ul>
</section>
<section id="slide-org5335d04">
<h3 id="org5335d04">Compara… Java 7…</h3>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Person</span>> <span style="color: #ffcc66;">people</span> = loadPeople();
Collections.sort(people, <span style="color: #99cc99;">new</span> <span style="color: #6699cc;">Comparator</span><<span style="color: #6699cc;">Person</span>>(){
<span style="color: #6699cc;">@Override</span>
<span style="color: #99cc99;">public</span> <span style="color: #6699cc;">int</span> <span style="color: #f99157;">compare</span> (<span style="color: #6699cc;">Person</span> <span style="color: #ffcc66;">p1</span>, <span style="color: #6699cc;">Person</span> <span style="color: #ffcc66;">p2</span>){
<span style="color: #99cc99;">return</span> p1.name.compareTo(p2.name)
}
})
</pre>
</div>
</section>
<section id="slide-org755abc2">
<h3 id="org755abc2">le transform</h3>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Person</span>> <span style="color: #ffcc66;">people</span> = loadPeople();
Collections.sort(people,
(<span style="color: #6699cc;">Person</span> <span style="color: #ffcc66;">p1</span>, <span style="color: #6699cc;">Person</span> <span style="color: #ffcc66;">p2</span>) -> p1.name.compareTo(p2.name)
)
</pre>
</div>
</section>
<section id="slide-org46b93f4">
<h3 id="org46b93f4">meh</h3>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Person</span>> <span style="color: #ffcc66;">people</span> = loadPeople();
Collections.sort(people,
(p1, p2) -> p1.name.compareTo(p2.name)
);
</pre>
</div>
</section>
<section id="slide-org6a7ed32">
<h3 id="org6a7ed32">Java 8</h3>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Person</span>> <span style="color: #ffcc66;">people</span> = loadPeople();
people.sort(p1, p2) -> p1.name.compareTo(p2.name));
</pre>
</div>
</section>
<section id="slide-org25173ce">
<h3 id="org25173ce">lambdas, buenas prácticas!</h3>
<ul class="fragment roll in">
<li>No usar paréntesis si solo hay un parámetro</li>
<li>No usar finals</li>
<li>No usar bloques!</li>
</ul>
</section>
<section id="slide-org9b7bf4b">
<h3 id="org9b7bf4b">Más ejemplos!</h3>
<div class="org-src-container">
<pre class="src src-java">(<span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">a</span>, <span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">b</span>) ­> a + b
</pre>
</div>
<div class="org-src-container">
<pre class="src src-java">(<span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">a</span>) ­> a + 1
</pre>
</div>
<div class="org-src-container">
<pre class="src src-java">(<span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">a</span>, <span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">b</span>) ­> { System.out.println(a + b); <span style="color: #99cc99;">return</span> a + b; }
</pre>
</div>
<div class="org-src-container">
<pre class="src src-java">() ­> <span style="color: #99cc99;">new</span> <span style="color: #6699cc;">ArrayList</span>()
</pre>
</div>
</section>
</section>
<section>
<section id="slide-orgb20f4fe">
<h2 id="orgb20f4fe">streams?</h2>
<div class="outline-text-2" id="text-orgb20f4fe">
</div></section>
<section id="slide-org1d05cc2">
<h3 id="org1d05cc2">Que son?</h3>
<p>
Un Stream es un modo de aplicar transformaciones a una secuencia de
elementos, por ejemplo una lista o datos a traves de la red (GET
HTTP), aplicando todas las transformaciones a la vez, elemento a
elemento.
</p>
</section>
<section id="slide-org108db04">
<h3 id="org108db04">Vamos a verlo mejor</h3>
<div class="figure">
<p><img src="./streams.jpg" alt="streams.jpg" />
</p>
</div>
</section>
<section id="slide-orgeeca322">
<h3 id="orgeeca322">but… again, why?</h3>
<p>
Antes de Java 8:
</p>
<ul>
<li>Tener una lista de elementos</li>
<li>Recorrerla una vez para aplicar una transformación</li>
<li>Recorrerla otra vez para aplicar otra transformación</li>
<li>Recor…. WUT</li>
<li>Pensar en una lógica de iteraccion para ahorrar repetir operaciones</li>
</ul>
<p>
Después de Java 8:
</p>
<ul>
<li>Tener una lista de elementos</li>
<li>Definir las transformaciones</li>
<li>Ejecutar una vez :D</li>
<li>No necesitamos pensar en una lógica muy complicada, nos abstrae de eso</li>
</ul>
</section>
<section id="slide-org1610ede">
<h3 id="org1610ede">Veamos un ejemplo</h3>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 7</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">String</span>> <span style="color: #ffcc66;">names</span> = <span style="color: #99cc99;">new</span> <span style="color: #6699cc;">ArrayList</span><>();
<span style="color: #99cc99;">for</span> (<span style="color: #6699cc;">Student</span> <span style="color: #ffcc66;">student</span> : students) {
<span style="color: #99cc99;">if</span>(student.getName().startsWith(<span style="color: #66cccc;">"A"</span>)){
names.add(student.getName());
}
}
</pre>
</div>
</div>
<div class="column" style="float:right; width: 50%">
<p>
<b><font color = "cyan">JAVA 8</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">string</span>> <span style="color: #ffcc66;">names</span> = students.stream()
.map(Student::getName)
.filter(name->name.startsWith(<span style="color: #66cccc;">"A"</span>))
.collect(Collectors.toList());
</pre>
</div>
</div>
</section>
</section>
<section>
<section id="slide-org67f10d1">
<h2 id="org67f10d1">optionals?</h2>
<div class="outline-text-2" id="text-org67f10d1">
</div></section>
<section id="slide-orgb61e86f">
<h3 id="orgb61e86f">Qué son?</h3>
<p>
Los Optionals, como su palabra dicen son un objeto que puede contener
o no un valor no nulo.
Este mola mucho.
</p>
<div class="figure">
<p><img src="./Optional.gif" alt="Optional.gif" />
</p>
</div>
</section>
<section id="slide-org57a0f2d">
<h3 id="org57a0f2d">Utilidad ?</h3>
<ul>
<li>No más NullPointer!</li>
<li>Centrarnos en los detalles de nuestro programa</li>
<li>Código más bonico</li>
</ul>
</section>
<section id="slide-org5a2f939">
<h3 id="org5a2f939">Como se usa?!</h3>
<ul>
<li class="fragment roll"></li>
<li class="fragment in">.get()</li>
<li class="fragment in">.orElse()</li>
<li class="fragment in">.orElseGet()</li>
</ul>
</section>
<section id="slide-orgffdcdcf">
<h3 id="orgffdcdcf">Veamos un ejemplo</h3>
<div class="org-src-container">
<pre class="src src-java">article.filter(a -> newerThanAMonth(a))
.orElseGet(() -> getNewestArticle());
</pre>
</div>
</section>
</section>
<section>
<section id="slide-orgaa4a070">
<h2 id="orgaa4a070">Think in functional</h2>
<div class="outline-text-2" id="text-orgaa4a070">
</div></section>
<section id="slide-org85c6ce9">
<h3 id="org85c6ce9">Funciones!</h3>
<p>
<b><font color = "cyan">forEach</font></b>
</p>
<ul>
<li>map</li>
<li>filter</li>
<li>collect</li>
<li>limit</li>
<li>sorted</li>
<li>flatMap</li>
</ul>
</section>
<section id="slide-orgdc85542">
<h3 id="orgdc85542">forEach</h3>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 7</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">Imprimimos cada elemento</span>
<span style="color: #99cc99;">for</span> (<span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">i</span> = 0; i < list.<span style="color: #6699cc;">size</span>(); i++) {
System.out.println(list.get(i));
}
</pre>
</div>
</div>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 8</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">Imprimimos cada elemento</span>
list.forEach(elemento ->
System.out.println(elemento)
);
</pre>
</div>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">Imprimimos cada elemento</span>
list.forEach(System.out::println);
</pre>
</div>
</div>
</section>
<section id="slide-orgefa2a07">
<h3 id="orgefa2a07">Funciones!</h3>
<ul>
<li>forEach</li>
</ul>
<p>
<b><font color = "cyan">map</font></b>
</p>
<ul>
<li>filter</li>
<li>collect</li>
<li>limit</li>
<li>sorted</li>
<li>flatMap</li>
</ul>
</section>
<section id="slide-orgc6ec32c">
<h3 id="orgc6ec32c">map</h3>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 7</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">result</span> =
<span style="color: #99cc99;">new</span> <span style="color: #6699cc;">ArrayList</span><<span style="color: #6699cc;">Integer</span>>();
<span style="color: #99cc99;">for</span> (<span style="color: #6699cc;">Integer</span> <span style="color: #ffcc66;">digit</span> : numbers) {
result.add(digit * digit);
}
</pre>
</div>
</div>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 8</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">squaresList</span> = numbers
.stream()
.map( i -> i*i)
.collect(Collectors.toList());
</pre>
</div>
</div>
</section>
<section id="slide-org1d00f98">
<h3 id="org1d00f98">Funciones!</h3>
<ul>
<li>forEach</li>
<li>map</li>
</ul>
<p>
<b><font color = "cyan">filter</font></b>
</p>
<ul>
<li>collect</li>
<li>limit</li>
<li>sorted</li>
<li>flatMap</li>
</ul>
</section>
<section id="slide-org5b839e8">
<h3 id="org5b839e8">filter</h3>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 7</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">Iterator</span><<span style="color: #6699cc;">Car</span>> <span style="color: #ffcc66;">carsIterator</span> = cars.iterator();
<span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">cont</span> = 0;
<span style="color: #99cc99;">while</span> (carsIterator.hasNext()) {
<span style="color: #6699cc;">Car</span> <span style="color: #ffcc66;">c</span> = carsIterator.next();
<span style="color: #99cc99;">if</span> (c.getCarColor() == <span style="color: #6699cc;">Color</span>.BLUE) {
cont ++;
}
}
}
</pre>
</div>
</div>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 8</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">get count of empty string</span>
<span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">count</span> = cars.stream()
.filter(car ->
car.getColor().equals(<span style="color: #6699cc;">Color</span>.Blue))
.count();
</pre>
</div>
</div>
</section>
<section id="slide-orgf1b390d">
<h3 id="orgf1b390d">Funciones!</h3>
<ul>
<li>forEach</li>
<li>map</li>
<li>filter</li>
</ul>
<p>
<b><font color = "cyan">limit</font></b>
</p>
<ul>
<li>limit</li>
<li>sorted</li>
<li>flatMap</li>
</ul>
</section>
<section id="slide-org100d7e4">
<h3 id="org100d7e4">collect</h3>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 7</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">result</span> = <span style="color: #99cc99;">new</span> <span style="color: #6699cc;">ArrayList</span><<span style="color: #6699cc;">Integer</span>>();
<span style="color: #99cc99;">for</span> (<span style="color: #6699cc;">Integer</span> <span style="color: #ffcc66;">digit</span> : numbers) {
result.add(digit * digit);
}
</pre>
</div>
</div>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 8</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">Function</span><<span style="color: #6699cc;">Integer</span>, <span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">square</span>=x -> x*x;
<span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">squareNumbers</span> = numbers
.stream()
.map(square)
.collect(Collectors.toList());
</pre>
</div>
</div>
</section>
<section id="slide-orgdeaac67">
<h3 id="orgdeaac67">Funciones!</h3>
<ul>
<li>forEach</li>
<li>map</li>
</ul>
<p>
<b><font color = "cyan">limit</font></b>
</p>
<ul>
<li>sorted</li>
<li>filter</li>
<li>flatMap</li>
</ul>
</section>
<section id="slide-org682087a">
<h3 id="org682087a">limit</h3>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 7</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #99cc99;">for</span>(<span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">i</span> = 0; i <= 10; i++) {
<span style="color: #6699cc;">Random</span> <span style="color: #ffcc66;">rnd</span> = <span style="color: #99cc99;">new</span> <span style="color: #6699cc;">Random</span>();
System.out.println(rnd.nextInt());
}
</pre>
</div>
</div>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 8</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">Random</span> <span style="color: #ffcc66;">random</span> = <span style="color: #99cc99;">new</span> <span style="color: #6699cc;">Random</span>();
random.ints().limit(10)
.forEach(System.out::println);
</pre>
</div>
</div>
</section>
<section id="slide-orgcd33efd">
<h3 id="orgcd33efd">Funciones!</h3>
<ul>
<li>forEach</li>
<li>map</li>
<li>filter</li>
<li>collect</li>
<li>limit</li>
</ul>
<p>
<b><font color = "cyan">sorted</font></b>
</p>
<ul>
<li>flatMap</li>
</ul>
</section>
<section id="slide-org55a64d5">
<h3 id="org55a64d5">sorted</h3>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 7</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java">Collections.sort(
nList,
Collections.reverseOrder());
<span style="color: #99cc99;">for</span>(<span style="color: #6699cc;">int</span> <span style="color: #ffcc66;">n</span>: nList) {
System.out.println(n);
}
</pre>
</div>
</div>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 8</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java">random.ints()
.limit(10)
.sorted()
.forEach(System.out::println);
</pre>
</div>
</div>
</section>
<section id="slide-org4d3df5a">
<h3 id="org4d3df5a">Funciones!</h3>
<ul>
<li>forEach</li>
<li>map</li>
<li>filter</li>
<li>collect</li>
<li>limit</li>
<li>sorted</li>
</ul>
<p>
<b><font color = "cyan">flatMap</font></b>
</p>
</section>
<section id="slide-orgbed6415">
<h3 id="orgbed6415">flatMap</h3>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 7</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">List</span><<span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>>> <span style="color: #ffcc66;">integerLists</span> =
Arrays.asList(
Arrays.asList(1, 2),
Arrays.asList(3, 4),
Arrays.asList(5)
)
<span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> flattened = <span style="color: #99cc99;">new</span> <span style="color: #6699cc;">ArrayList</span><>();
<span style="color: #99cc99;">for</span>(<span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">integerList</span> : integerLists)
{
flattened.addAll(integerList);
}
<span style="color: #99cc99;">for</span> (<span style="color: #6699cc;">Integer</span> <span style="color: #ffcc66;">i</span> : flattened)
{
System.out.println(i);
}
</pre>
</div>
</div>
<div class="column" style="float:left; width: 50%">
<p>
<b><font color = "cyan">JAVA 8</font></b>
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">List((1,2), (3, 4), (5))</span>
<span style="color: #6699cc;">Stream</span><<span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>>> <span style="color: #ffcc66;">integerListStream</span> =
Stream.of(
Arrays.asList(1, 2),
Arrays.asList(3, 4),
Arrays.asList(5)
);
<span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">List(1, 2, 3, 4, 5)</span>
<span style="color: #6699cc;">Stream</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">integerStream</span> =
integerListStream
.flatMap(Collection::stream)
.forEach(System.out::println);
</pre>
</div>
</div>
</section>
</section>
<section>
<section id="slide-org10b5673">
<h2 id="org10b5673">Composition!!</h2>
<div class="outline-text-2" id="text-org10b5673">
</div></section>
<section id="slide-org7612931">
<h3 id="org7612931">Que es?</h3>
<p>
Composición?
Es la unión de varias de las anteriores funciones, como ya hemos visto
en algunos de los ejemplos.
Pero no solo eso, también funcionan con los optionals!
</p>
<div class="figure">
<p><img src="./giphy.gif" alt="giphy.gif" />
</p>
</div>
</section>
<section id="slide-org741af84">
<h3 id="org741af84">Veamos algunos ejemplos normales</h3>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">Imaginemos que tenemos una lista "list" de elementos del 0 al 9</span>
<span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]</span>
<span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">lSquare</span> =
list.map(numero -> numero*numero).collect(Collectors.toList());
<span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">lFiltradaPar</span> =
lSquare.filter(numero -> numero % 2 ==0).collect(Collectors.toList());
<span style="color: #999999; font-style: italic;">// </span><span style="color: #999999; font-style: italic;">SE pueden unir</span>
<span style="color: #6699cc;">List</span><<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">lUnidas</span> =
list
.map(numero -> numero*numero)
.filter(numero -> numero % 2 == 0)
.collect(Collectors.toList());
</pre>
</div>
</section>
<section id="slide-org71df2a9">
<h3 id="org71df2a9">Como componer funciones</h3>
<p>
Si tu tienes una función tal que
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">Function</span><<span style="color: #6699cc;">Integer</span>,<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">add3</span> = (a) -> a + 3 ;
</pre>
</div>
<p>
y otra que
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">Function</span><<span style="color: #6699cc;">Integer</span>,<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">times2</span> = (a) -> a * 2 ;
</pre>
</div>
<p>
Puedes "unirlas", componerlas, decir que la salida de una, sea la
entrada de la otra
</p>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #6699cc;">Function</span><<span style="color: #6699cc;">Integer</span>,<span style="color: #6699cc;">Integer</span>> <span style="color: #ffcc66;">composedA</span> = add3.compose( times2 ) ;
</pre>
</div>
</section>
<section id="slide-org7a01cef">
<h3 id="org7a01cef">Ahora con optionals</h3>
<div class="outline-text-3" id="text-org7a01cef">
</div></section>
<section id="slide-org847e7a6">
<h4 id="org847e7a6">Java 7</h4>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #99cc99;">if</span>(opt.isPresent() && opt.get().contains(<span style="color: #66cccc;">"ab"</span>)) {
System.out.println(opt.get());
}
</pre>
</div>
</section>
<section id="slide-org10913c7">
<h4 id="org10913c7">Java 8 con optionals</h4>
<div class="org-src-container">
<pre class="src src-java">opt.
filter(x -> x.contains(<span style="color: #66cccc;">"ab"</span>)).
ifPresent(System.out::println);
</pre>
</div>
</section>
<section id="slide-org916d66e">
<h4 id="org916d66e">Java 8 con flatMaps</h4>
<div class="org-src-container">
<pre class="src src-java"><span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">Imagina una funcion que no puede recibir un null </span>
<span style="color: #99cc99;">public</span> <span style="color: #6699cc;">String</span> <span style="color: #f99157;">findSimilar</span>(<span style="color: #6699cc;">@NotNull</span> <span style="color: #6699cc;">String</span> <span style="color: #ffcc66;">s</span>) <span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">...</span>
<span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">Para usarla seria...</span>
String similarOrNull = x != <span style="color: #6699cc;">null</span>? findSimilar(x) : <span style="color: #6699cc;">null</span>;
<span style="color: #999999; font-style: italic;">// </span><span style="color: #999999; font-style: italic;">Con map ...</span>
<span style="color: #6699cc;">Optional</span><<span style="color: #6699cc;">String</span>> <span style="color: #ffcc66;">similar</span> = opt.map(<span style="color: #99cc99;">this</span>::findSimilar);
<span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">Esto devolveria un null si contiene null y si no lo ejecutaria pero... </span>
<span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">tenemos Optionals</span>
<span style="color: #99cc99;">public</span> <span style="color: #6699cc;">Optional</span><<span style="color: #6699cc;">String</span>> <span style="color: #f99157;">tryFindSimilar</span>(<span style="color: #6699cc;">String</span> <span style="color: #ffcc66;">s</span>) <span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">...</span>
<span style="color: #999999; font-style: italic;">//</span><span style="color: #999999; font-style: italic;">Usando el map aqui nos daria un optional de optional por eso</span>
<span style="color: #6699cc;">Optional</span><<span style="color: #6699cc;">Optional</span><<span style="color: #6699cc;">String</span>>> bad = opt.map(<span style="color: #99cc99;">this</span>::tryFindSimilar);
<span style="color: #6699cc;">Optional</span><<span style="color: #6699cc;">String</span>> <span style="color: #ffcc66;">similar</span> = opt.flatMap(<span style="color: #99cc99;">this</span>::tryFindSimilar);
</pre>
</div>
</section>
</section>
<section>
<section id="slide-org028ec7f">
<h2 id="org028ec7f">Exercises</h2>
</section>
</section>
<section>
<section id="slide-orgfcf83be">
<h2 id="orgfcf83be">Resumen</h2>
<ul>
<li>Java 8 rules!</li>
<li>Puede parecer muy diferente al principio</li>
<li>Vital para rediseñar tu código y mejorarlo</li>
<li>Aprende funcional, te facilitará tu forma de programar, de pensar y
de vivir!</li>
</ul>
<div class="figure">
<p><img src="./functional.jpg" alt="functional.jpg" width="300px" />
</p>
</div>
</section>
</section>
<section>
<section id="slide-orgf434cf1">
<h2 id="orgf434cf1">ty!</h2>
<p>
ACM y [ACM-SIG] Scala<br />
Roberto Sarmiento (Todos me llaman Ashida so… Ashida xD)<br />
Telegram: @Ashida<br />
<img src="./ACM.png" alt="ACM.png" />
</p>
</section>
</section>
</div>
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