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| </div><div id='content' class='page-1'><div class='row'><div class='row-fluid'><div class='col-lg-3'><ul class='nav-sidebar'><li><a href='./'>Blog index</a></li><li class='active'><a href='#doc'>Zipping Collections with Groovy</a></li><li><a href='#_what_is_zipping' class='anchor-link'>What is zipping?</a></li><li><a href='#_groovy' class='anchor-link'>Groovy</a></li><li><a href='#_eclipse_collections' class='anchor-link'>Eclipse Collections</a></li><li><a href='#_guava' class='anchor-link'>Guava</a></li><li><a href='#_streamex' class='anchor-link'>StreamEx</a></li><li><a href='#_vavr' class='anchor-link'>Vavr</a></li><li><a href='#_jooλ' class='anchor-link'>jOOλ</a></li><li><a href='#_groovy_gquery' class='anchor-link'>Groovy GQuery</a></li><li><a href='#_more_information' class='anchor-link'>More information</a></li></ul><br/><ul class='nav-sidebar'><li style='padding: 0.35em 0.625em; background-color: #eee'><span>Related posts</span></li><li><a href='./groovy-list-processing-cheat-sheet'>Groovy List Processing Cheat Sheet</a></li><li><a href='./groovy-null-processing'>Groovy Processing Nulls In Lists</a></li><li><a href='./parsing-json-with-groovy'>Parsing JSON with Groovy</a></li><li><a href='./deep-learning-and-eclipse-collections'>Deep Learning and Eclipse Collections</a></li><li><a href='./comparators-and-sorting-in-groovy'>Comparators and Sorting in Groovy</a></li><li><a href='./wordle-checker'>Checking Wordle with Groovy</a></li><li><a href='./fruity-eclipse-collections'>Fruity Eclipse Collections</a></li><li><a href='./adventures-with-groovyfx'>Adventures with GroovyFX</a></li><li><a href='./deck-of-cards-with-groovy'>Deck of cards with Groovy, JDK collections and Eclipse Collections</a></li><li><a href='./lego-bricks-with-groovy'>Lego Bricks with Groovy</a></li><li><a href='./groovy-haiku-processing'>Groovy Haiku processing</a></li><li><a href='./helloworldemoji'>Hello World with Emojis</a></li></ul></div><div class='col-lg-8 col-lg-pull-0'><a name='doc'></a><h1>Zipping Collections with Groovy</h1><p><span>Author: <i>Paul King</i></span><br/><span>Published: 2022-11-17 12:50PM</span></p><hr/><div class="sect1"> |
| <h2 id="_what_is_zipping">What is zipping?</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>In computer science, <a href="https://en.wikipedia.org/wiki/Zipping_(computer_science)">zipping</a> translates sequences into sequences where, if visualized in two dimensions, the rows and columns are swapped. So the zip of:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">[['a', 'b', 'c'], |
| [ 1 , 2 , 3 ]]</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>would be:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">[['a', 1], |
| ['b', 2], |
| ['c', 3]]</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>It’s a very handy operation and depending on the language, may be supported for tuples, lists, streams and other sequences or aggregates.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Java collections and streams don’t currently support such functionality out-of-the-box with various workarounds discussed <a href="https://dzone.com/articles/bridge-the-gap-of-zip-operation">here</a>. The summary: language and library design is hard; any zip implementation that Java provides would have some limitations baked in, so they instead provide the necessary primitives to allow folks to build their own implementations based on their specific requirements.</p> |
| </div> |
| <div class="paragraph"> |
| <p>We’ll look at what Groovy provides and some of the available Java libraries that you can also use. The same caveats apply to these libraries, each will have its own implementation strengths and weaknesses.</p> |
| </div> |
| <div class="paragraph"> |
| <p>We’ll use an example inspired by this <a href="https://twitter.com/TheDonRaab">Donald Raab</a> <a href="https://donraab.medium.com/make-or-append-me-a-string-c654f247373a">blog post</a>. It looks at zipping (and formatting) lists of strings containing "fall"-inspired emoji. Yes, it’s late spring for the southern hemisphere who also mostly call fall "autumn", but hopefully everyone will appreciate the inspiration.</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/fall_emojis.png" alt="some fall inspired emojis" width="741"></span></p> |
| </div> |
| <hr> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_groovy">Groovy</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>Groovy uses the <code>transpose</code> method for zipping:</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/ZippingCollectionsGroovy.png" alt="zipping example with Groovy"></span></p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_eclipse_collections">Eclipse Collections</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>Eclipse Collections has a <code>zip</code> method on its list classes:</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/ZippingCollectionsEC.png" alt="zipping example with Eclipse Collections"></span></p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_guava">Guava</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>Guava has a streams utility class with a <code>zip</code> method:</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/ZippingCollectionsGuava.png" alt="zipping example with Guava"></span></p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_streamex">StreamEx</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>StreamEx provides an enhanced stream library which supports <code>zipWith</code>:</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/ZippingCollectionsStreamEx.png" alt="zipping example with StreamEx"></span></p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_vavr">Vavr</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>Vavr has a <code>zipWith</code> method on its list class:</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/ZippingCollectionsVavr.png" alt="zipping example with Vavr"></span></p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_jooλ">jOOλ</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>jOOλ has a <code>zip</code> method for its sequences:</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/ZippingCollectionsJool.png" alt="zipping example with jOOλ"></span></p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_groovy_gquery">Groovy GQuery</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>If you are a fan of query-like DSLs, Groovy’s language integrated query, GQuery (AKA GINQ), can also be used:</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/ZippingCollectionsGQ.png" alt="zipping example with GQuery"></span></p> |
| </div> |
| <div class="paragraph"> |
| <p>This uses a special <code>_rn</code> "row number" pre-defined variable in GQ expressions. It follows the same strategy as the IntStream "workaround" for Java mentioned in this <a href="https://www.baeldung.com/java-collections-zip">blog</a>.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_more_information">More information</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>The code examples can be found in the <a href="https://github.com/paulk-asert/zipping-collections">repo</a></p> |
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