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<!doctype html>
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<title>Guava 12+, organizing a dev's mind and the codebase for FluentIterable and Optional</title>
<meta name="description" content="Guava 12+, organizing a dev's mind and the codebase for FluentIterable and Optional">
<meta name="author" content="Sébastien Lesaint @ SonarSource">
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<body>
<div class="reveal">
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<div class="slides">
<section>
<h1>Guava 12+</h1>
<h3>organizing a dev's mind and the codebase for FluentIterable and Optional</h3>
</section>
<section>
<section>
<h2>FluentIterable</h2>
<small>(added in Guava 12)</small>
<p>Its streams and functional programming for the poor</p>
<p>say bye bye to loops, nested loops, mutable variables, ...</p>
</section>
<section>
<h2>Old style</h2>
<img src="assets/img/imperative_vs_functional_imperative.png">
<p class="fragment">Extract the 40 first lines starting with ERROR from the specified list</p>
</section>
<section>
<h2>Functional style</h2>
<img src="assets/img/imperative_vs_functional_functional.png">
<ul>
<li>code is much shorter</li>
<li>no more mutable variable</li>
</ul>
</section>
<section>
<h2>Imperative VS functional</h2>
<img src="assets/img/imperative_vs_functional_tweet_mario_fusco.png"><br/>
<small>note: we are close to Java 8 stream syntax</small>
</section>
<section>
<h2>a real change</h2>
<p>even though it's nothing but a fluent style wrapper<br/>
<img src="assets/img/imperative_vs_functional_old_way.png"><br/>
</p>
</section>
<section>
<h2>Keep it readable</h2>
<p>IDEA lambda style display<br/>
<img src="assets/img/idea_tidy_display.png"><br/>
the real code<br/>
<img src="assets/img/without_idea_tidy_display.png">
</p>
</section>
<section>
<h2>Keep it readable</h2>
<p>use a method<br/>
<img src="assets/img/use_is_error_method.png">
</p>
</section>
<section>
<h2>Keep it readable</h2>
use indent, otherwise...<br/>
<img src="assets/img/no_indent.png">
</section>
<section>
<h2>Keep it readable</h2>
use static import of FluentIterable.from<br/>
<img src="assets/img/static_import_from.png">
</section>
</section>
<section>
<h2>let's go practical</h2>
</section>
<section>
<section>
<h2>Legacy code 1</h2>
<img src="assets/img/findAllOpenSourceCompatiblePlugins_old_way.png">
<p class="fragment">Find all opensource plugins which are compatible with the current version of SQ</p>
</section>
<section>
<h2>Functional style</h2>
<img src="assets/img/findAllOpenSourceCompatiblePlugins_new_way_short.png">
</section>
<section>
<h2>the whole stuff</h2>
<img src="assets/img/findAllOpenSourceCompatiblePlugins_new_way.png">
</section>
<section>
<h2>handling Null</h2>
<img src="assets/img/findAllOpenSourceCompatiblePlugins_new_way_notNull.png">
</section>
<section>
<h2>Nonnull Predicates</h2>
<ul>
<li>
complies with Javadoc
<img src="assets/img/javadoc_predicate_apply.png">
</li>
<li>override @Nullable with @Nonnull
<ul>
<li>complies with SQ</li>
<li>but not with IDEA (who cares?)</li>
</ul>
</li>
<li>Fail early in predicate
<ul>
<li>enforces explicit Null handling in stream</li>
<li>or avoid numerous useless null checks</li>
</ul>
</li>
</ul>
</section>
<section>
<h2>save useless instance creation</h2>
<img src="assets/img/findAllOpenSourceCompatiblePlugins_new_way_must_remove_new.png">
</section>
<section>
<h2>singleton enum</h2>
<p>
when apply code is static
<img src="assets/img/singleton_enum.png">
</p>
</section>
<section>
<h2>save useless instance creation</h2>
<img src="assets/img/findAllOpenSourceCompatiblePlugins_new_way_must_remove_new.png">
</section>
<section>
<h2>predicate as property</h2>
<p>
when apply code depends only on a instance properties
<img src="assets/img/predicate_property.png">
</p>
</section>
<section>
<h2>final code</h2>
<img src="assets/img/findAllOpenSourceCompatiblePlugins_new_way_final_code.png">
</section>
</section>
<section>
<section>
<h2>Legacy code 2</h2>
<p><img src="assets/img/get_A_OpenSourceDevelopers_old.png"></p>
<p class="fragment">create an ordered collection of the developers of the opensource plugins in the specified collection which name starts with an a (case insensitive)</p>
</section>
<section>
<h2>Functional style</h2>
<img src="assets/img/get_A_OpenSourceDevelopers_new.png">
</section>
<section>
<h2>transform And Concat</h2>
<small>Also known as flatMap (map and flatten)</small>
<pre>
PluginA ---- PluginB ---- PluginC ---- PluginD
| | | |
| | | |
DevA() ---- DevB() ---- DevC() ---- DevC()
\ \ / /
\ \ / /
\ \ / /
--------------------\ /---------------------
|
DevAll[]
</pre>
</section>
<section>
<h2>Know your FluentIterable</h2>
<table>
<thead>
<tr>
<th>process input</th>
<th><u>immutable</u> output</th>
<th>Optional output</th>
</tr>
</thead>
<tbody>
<tr>
<td>
filter
<br/><br/>
transform,
transformAndConcat
<br/><br/>
cycle, append
</td>
<td>
toList, toSet, toArray
<br/><br/>
toSortedList, toSortedSet
<br/><br/>
toMap, index, uniqueIndex
</td>
<td>
first, last
<br/><br/>
firstMatch, anyMatch
</td>
<tr>
</tbody>
</table>
</section>
</section>
<section>
<section>
<h2>Under the hood</h2>
<p>What you should known to avoid bad usage of FluentIterable</p>
</section>
<section>
<h2>Lazy evaluation</h2>
<p>all filter/map/flatmap operations are lazy evaluated</p>
<ul>
<li>empty iterable at any point means next operations are not evaluated</li>
<li>iterate twice means do all operations twice</li>
<li>same goes with exist, find, any, size, get, ...</li>
</ul>
</section>
<section>
<h2>practices</h2>
<ul>
<li>don't return FluentIterable directly in non private functions</li>
<li>be careful when storing a FluentIterable in variable</li>
<li>but you can reuse a FluentIterable to create variations</li>
</ul>
</section>
<section>
<h2>Immutability</h2>
<p>Ouput of toList, toSet, toMap are immutable objects</p>
<ul>
<li>it's good for your public functions</li>
<li>
for mutable collections, use Guava's methods
<ul>
<li>
do<br>
<img src="assets/img/mutable_list_do.png" width="150%" height="150%">
</li>
<li>
do not<br/>
<img src="assets/img/mutable_list_dont.png" width="150%" height="150%">
</li>
</ul>
</li>
</ul>
</section>
<section>
<h2>lots of objects</h2>
<p>Guava create lots of (short-lived) objects</p>
<p>So, try and don't add to the stack with your objects</p>
</section>
</section>
<section>
<section>
<h2>Organising functions/predicates</h2>
<ul>
<li>
use factory-style classes
<ul>
<li>
static methods are static import friendly<br/>
=> short and good readibility
</li>
<li>don't expose inner singleton enums or classes</li>
</ul>
</li>
</ul>
</section>
<section>
<h2>PluginPredicates</h2>
<img src="assets/img/PluginPredicates.png">
</section>
<section>
<h2>Guidelines</h2>
<ul>
<li>
group per domain class
</li>
<li>
Name is plural
<ul>
<li>eg. "PluginPredicates", "PluginFunctions"</li>
</ul>
</li>
<li>
group factory classes per domain into a package
<ul>
<li>eg. "updatecenter.function", "updatecenter.predicate"</li>
</ul>
</li>
</ul>
</section>
</section>
<section>
<section>
<h2>Optional</h2>
<p> </p>
<h3 class="fragment">Get rid of null...</h3>
<h3 class="fragment">... as a returned value</h3>
<p> </p>
<small class="fragment">(added in Guava 10 so we should already use it!)</small>
</section>
<section>
<h2>Optional as a return type</h2>
<ul>
<li>
improves meaning of method signature<br/>
<img src="assets/img/findNewestUpdate_nullable.png" width="150%" height="150%"><br/>
<img src="assets/img/findNewestUpdate_Optional.png" width="150%" height="150%"><br/>
</li>
<li>less error prone</li>
<li>no more @CheckForNull or @Nullable or javadoc or whatever</li>
</ul>
</section>
<section>
<h2>Optional as a parameter</h2>
<p> </p>
<h3 class="fragment">don't do it in public methods</h3>
<p> </p>
<blockquote class="fragment">Rubustness principle: Be conservative in what you send, be liberal in what you accept</blockquote>
</section>
<section>
<h2>Optional as a parameter</h2>
<ul class="fragment">
<li>keep using @Nullables
<ul>
<li>avoids polluting method signature</li>
<li>and add extra constraint on method caller</li>
</ul>
</li>
<li>use Optional.fromNullable internally</li>
</ul>
</section>
<section>
<h2>Optional as a property</h2>
<p> </p>
<h3 class="fragment">don't do it either</h3>
<ul class="fragment">
<li>The extra storage cost is just not worth it</li>
<li>keep using (or do use) @CheckForNull/@Nullable</li>
<li>Use Optional.fromNullable in getters</li>
</ul>
</section>
<section>
<h2>No more null checks</h2>
<p>forget testing null, use Optional.isPresent</p>
<img src="assets/img/use_is_present_simple.png" width="150%" height="150%">
<p>never use Optional.get without Option.isPresent first</p>
</section>
<section>
<h2>The golden or method</h2>
<p>
elegant default value<br/>
<img src="assets/img/use_or_for_default_value.png" width="150%" height="150%">
</p>
<p>
use Optional.orNull if null is your default value<br/>
<img src="assets/img/use_or_null.png" width="150%" height="150%">
</p>
</section>
<section>
<h2>Or even better</h2>
<p>
fluent method calls<br/>
<img src="assets/img/use_combined_ors.png" width="150%" height="150%">
</p>
<p>
or throwing exceptions<br/>
<img src="assets/img/use_or_to_throw_exception.png" width="150%" height="150%">
</p>
</section>
</section>
</div>
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