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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Java 8: A quick overview over the good parts - Writing Java has never been so fun</title>
<meta name="description" content="Java 8: A quick overview over the good parts">
<meta name="author" content="Benjamin Schmid | @bentolor">
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<body>
<div class="reveal">
<!-- Any section element inside of this container is displayed as a slide -->
<div class="slides">
<section>
<h1 style="margin: 50px 0 .3em">Java 8<br/>The good parts</h1>
<h3 style="font-size:1.2em;margin-bottom:2em">Writing Java has never been so fun</h3>
<p style="text-align: right">
<a href="https://twitter.com/bentolor">@bentolor</a>
</p>
</section>
<section>
<h2>Table of contents</h2>
<p style="font-size: 76%; text-align: center; color: #666; margin: -1.5em 0 1em 0">Usage hint: Use mouse scoll or cursor right & <strong>down</strong> to navigate!</p>
<div id="table-of-contents"></div>
</section>
<section class="glow">
<section>
<h2 class="slide-header">Java 8 is <em>big</em></h2>
<h5>Language</h5>
<ul>
<li>Lambdas & Functional Interfaces</li>
<li>Method References</li>
<li>Default Methods</li>
<li>Better annotations</li>
<li>Better Type Inference</li>
</ul>
</section>
<section>
<h2>Java 8 is <em>big</em></h2>
<h5>Runtime library</h5>
<ul>
<li>Streams</li>
<li>Optional</li>
<li>Multicore Support (Parallel)</li>
<li>Native Javascript</li>
<li>Many Goodies</li>
</ul>
</section>
<section>
<h2>Java 8 is <em>big</em></h2>
<h5>Compiler & Tools</h5>
<ul>
<li>Reflection: Parameter names</li>
<li>CLI: jjs (Nashorn)</li>
<li>CLI: jdeps</li>
<li>Death of PermGen</li>
</ul>
</section>
</section>
<section>
<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Language changes</h2>
</section>
<section>
<section>
<h2 class="slide-header">Lambdas</h2>
<p>Basic form</p>
<pre><code class="java">(params) -> expression
(params) -> statement
(params) -> { statements }</code></pre>
<p class="tgap">A simple example (no parameters):</p>
<pre><code class="java">Runnable r = () -> System.out.println("Hello!");
r.run();</code></pre>
<p class="tgap">Example with parameter (Type inferred!)<p>
<pre><code class="java">Arrays.asList( "a", "b", "d" ).forEach( e -> System.out.println( e ) );</code></pre>
</section>
<section>
<h2>Lambdas</h2>
<p>Lambdas can access outer field / variables if they are <em>(effectively)</em> final</p>
<pre><code class="java">String separator = ",";
Arrays.asList( "a", "b", "d" )
.forEach( (String e) -> System.out.print(e+separator) );
//separator = ";" // would break!</code></pre>
<p class="tgap">Lambdas may return values (inline/explicit)</p>
<pre><code class="java">Arrays.asList( "a", "b", "d" ).sort( ( e1, e2 ) -> e1.compareTo( e2 ) );
// or:
Arrays.asList( "a", "b", "d" ).sort( ( e1, e2 ) -> {
return e1.compareTo( e2 );
} ); </code></pre>
</section>
</section>
<section>
<section>
<h2 class="slide-header">Functional interfaces</h2>
<pre><code class="java">Comparator <Apple> c =
(Apple a1, Apple a2) -> a1.getWeight().compareTo(a2.getWeight());</code></pre>
<h5 class="fragment tgap">Wait, wait, wait... Comparator? How does this work?</h5>
<pre class="fragment"><code class="java">@FunctionalInterface
public interface Comparator<T> {
int compare(T o1, T o2);
}</code></pre>
</section>
<section>
<h2><code>@FunctionalInterface</code></h2>
<p> Conceptually, a functional interface has exactly <strong>one abstract
method.</strong> As such, it may be implicitly converted to a lambda expression.</p>
<p>Note that <strong>instances of functional interfaces</strong> can be created with
<em>lambda expressions</em> or method/constructor references. </p>
<p><strong>But:</strong> To avoid breakage by accidently adding further methods , these
interfaces <strong><u>should</u></strong> be explicitly tagged with <code>@FunctionalInterface</code>.
</p>
</section>
</section>
<section>
<section>
<h2 class="slide-header">Interface <code>default</code> methods</h2>
<p>In Java 8 you can write:</p>
<pre><code class="java">List<Integer> numbers = Arrays.asList(3, 5, 1, 2, 6);
numbers.sort(Comparator.naturalOrder());</code></pre>
<p class="tgap fragment">Huh? <code>java..util.List</code> now requires a <code>sort()</code>-Method?<br/>Will all of my code break now?</p>
<pre class="fragment"><code class="java">public interface List<E> extends Collection<E> {
// ...
default void sort(Comparator<? super E> c) {
// ...
}
}</code></pre>
</section>
<section>
<h2 class="slide-header">Interface <code>static</code> methods</h2>
<pre><code class="java">private interface PersonFactory {
// Interfaces now allow static methods
static Person createPerson( String firstname, String lastname ) {
return new Person(firstname, lastname);
}
}</code></pre>
</section>
</section>
<section>
<section>
<h2 class="slide-header">Method references</h2>
<p>Given the following interface</p>
<pre><code class="java mb-30">public interface MyFormatter<T> {
String format(T object);
}
public <T> String format(T o, MyFormatter<T> formatter) {
return formatter.format(o);
}</code></pre>
<div class="fragment tgap">
<p>We can simply reuse existing other implementations</p>
<pre><code class="java">format(32, Integer::toHexString)</code></pre>
</div>
</section>
<section>
<h2 >Supported method references</h2>
<ul>
<li><strong>static method:</strong> <code>Class::staticMethodName</code></li>
<li><strong>instance method of a <em>particular</em> object</strong> <code>object::methodName</code></li>
<li><strong>instance method of an <em>arbitrary</em> object</strong> <code>Type::methodName</code></li>
<li><strong>constructor:</strong> <code>ClassName::new</code></li>
</ul>
</section>
</section>
<section>
<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Runtime library enhancement</h2>
</section>
<section>
<section>
<h2 class="slide-header">Streams</h2>
<pre><code class="java mb-30">Collection<Task> tasks = getTasks();
long totalPointsOfOpenTasks = tasks
.stream()
.filter( task -> task.getStatus() == Status.OPEN )
.mapToInt( Task::getPoints )
.sum();
System.out.println( "Total points: " + totalPointsOfOpenTasks );</code></pre>
</section>
<section>
<h2 class="slide-header">Stream operations</h2>
<h4>Are divided into</h4>
<ul class="mb-30">
<li><em>Intermediate operations</em> (returning another <code>Stream<T></code>)</li>
<li><em>Terminal operations</em> (returning the final result)</li>
</ul>
<h4>Parallel processing</h4>
<p>Out-of-the box support of parallel processing (Multi-threading!)</p>
<p><pre><code>stream.parallel()</code></pre></p>
</section>
<section>
<h2 class="slide-header">Complex stream example</h2>
<pre><code class="java mb-30">// Calculate the weight of each tasks (as percent of total points)
final Collection<String> result = tasks
.stream() // Stream<String>
.mapToInt( Task::getPoints ) // IntStream
.asLongStream() // LongStream
.mapToDouble( points -> points / totalPoints ) // DoubleStream
.boxed() // Stream<Double>
.mapToLong( weigth -> ( long )( weigth * 100 ) ) // LongStream
.mapToObj( percentage -> percentage + "%" ) // Stream<String>
.collect( Collectors.toList() ); // List<String>
System.out.println( result );</code></pre>
</section>
</section>
<section>
<h2 class="slide-header">Optional</h2>
<p>Allows you to commit to a non-<code>null</code> convention in your project
<br/> & offers some convenience. </p>
<pre><code class="java mb-30">Optional<String> fullName = Optional.ofNullable( null );</code></pre>
<pre><code class="java mb-30">log.info( "Full Name is set? " + fullName.isPresent() );
log.info( "Full Name: " + fullName.orElseGet( () -> "[none]" ) );
log.info( fullName.map( s -> "Hey " + s + "!" ).orElse( "Hey Stranger!" ) );</code></pre>
<p>No more <code>NullPointerException</code>?</p>
</section>
<section>
<h2 class="slide-header">Native Javascript Support (Nashorn)</h2>
<h5>Use / Run Javascript in your code:</h5>
<pre><code class="java mb-30">ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName( "JavaScript" );
System.out.println( engine.eval( "function f() { return 1; }; f() + 1;" ) );</code></pre>
<h5>From command line</h5>
<pre><code class="mb-30">jjs server.js</code></pre>
</section>
<section>
<section>
<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Smaller goodies</h2>
</section>
<section>
<h2 class="slide-header">Better Annotations</h2>
<h5>Repeatable</h5>
<pre><code class="java mb-30">@Filter( "filter1" )
@Filter( "filter2" )
public interface Filterable { }</code></pre>
<h5>... assigned to variables, constructors, maps, casts, ...</h5>
<pre><code class="java mb-30">@NotNull String myString = "Foo"
new @Interned MyObject()
myString = (@NonNull String) myObject;</code></pre>
<h5>... used in Generics</h5>
<pre><code class="java mb-30">List<@Email String> emails = ...</code></pre>
<h5>... and more!</h5>
</section>
<section>
<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Better type inference</h2>
</section>
<section>
<h2 class="slide-header">Parameter names</h2>
<pre><code class="java mb-30">Method method = ParameterNames.class.getMethod( "main", String[].class );
for( final Parameter parameter: method.getParameters() ) {
System.out.println( "Parameter: " + parameter.getName() );
}</code></pre>
</section>
<section>
<h2 class="slide-header"> Date/Time API (JSR 310)</h2>
<ul>
<li>More convenience & easier operations. </li>
<li>Time-zone less data types (i.e. <code>LocalDate</code>) </li>
</ul>
</section>
<section>
<h2 class="slide-header"><code>java.util.Base64</code></h2>
</section>
<section>
<h2 class="slide-header">Better Multithreading support</h2>
<ul>
<li><code>list.parallelStream()</code></li>
<li><code>stream.parallel()</code></li>
<li><code>ConcurrentMap.parallelStream()</code></li>
<li><code>Arrays.parallelSort()</code></li>
<li><code>Arrays.parallelSetAll()</code></li>
</ul>
</section>
<section>
<h2 class="slide-header">Small enhancements in <code>java.util.concurrent</code></h2>
</section>
</section>
<section>
<section>
<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Tools & JVM</h2>
</section>
<section>
<h2 class="slide-header">jdeps</h2>
<p>Class dependency analyzer</p>
<pre><code class="mb-30">$ jdeps org.springframework.core-3.0.5.jar
org.springframework.core-3.0.5.jar -> lib\rt.jar
org.springframework.core (org.springframework.core-3.0.5.jar)
-> java.io
-> java.lang
-> java.lang.annotation
-> java.lang.ref
-> java.lang.reflect
-> java.util
-> java.util.concurrent
-> org.apache.commons.logging not found
-> org.springframework.asm not found
org.springframework.core.annotation (org.springframework.core-3.0.5.jar)
-> java.lang
-> java.lang.annotation
-> java.lang.reflect
-> java.util</code></pre>
</section>
<section>
<h2 class="slide-header">PermGen is now <br/><a href="http://www.javacodegeeks.com/2013/02/java-8-from-permgen-to-metaspace.html">MetaSpace</a></h2>
</section>
</section>
<section>
<h2 class="slide-header">Resources</h2>
<ul>
<li><a href="http://www.javacodegeeks.com/2014/05/java-8-features-tutorial.html#new_java_tools">Java 8 Features – The ULTIMATE Guide</a></li>
<li><a href="http://java.dzone.com/articles/whats-wrong-java-8-part-vi">Whats wrong with Java 8</a></li>
<li><a href="http://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html#StreamOps">Streams API</a></li>
<li><a href="https://github.com/java8/Java8InAction/">Java 8 in Action</a></li>
</ul>
</section>
<section>
<h3 style="font-size:3em;margin-top:30px;margin-bottom:.5em">Thank you :)</h3>
</section>
</div>
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