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diff --git a/.html/java/a-new-kind-of.html b/.html/java/a-new-kind-of.html deleted file mode 100644 index 764fb45..0000000 --- a/.html/java/a-new-kind-of.html +++ /dev/null @@ -1,203 +0,0 @@ -<!DOCTYPE html> -<html> -<head> - <title> - The Codex » - A New Kind of Java - </title> - - <link - rel='stylesheet' - type='text/css' - href='http://fonts.googleapis.com/css?family=Buenard:400,700&subset=latin,latin-ext'> - <link - rel="stylesheet" - type="text/css" - href="../media/css/reset.css"> - <link - rel="stylesheet" - type="text/css" - href="../media/css/grimoire.css"> -</head> -<body> - -<div id="shell"> - - <ol id="breadcrumbs"> - - <li class="crumb-0 not-last"> - - <a href="../">index</a> - - </li> - - <li class="crumb-1 not-last"> - - <a href="./">java</a> - - </li> - - <li class="crumb-2 last"> - - a-new-kind-of - - </li> - - </ol> - - - - <div id="article"> - <h1 id="a-new-kind-of-java">A New Kind of Java</h1> -<p>Java 8 is almost here. You can <a href="http://jdk8.java.net/download.html">play with the early access -previews</a> right now, and I think you -should, even if you don't like Java very much. There's so much <em>potential</em> in -there.</p> -<h2 id="the-one-more-thing">The “One More Thing”</h2> -<p>The Java 8 release comes with a slew of notable library improvements: the new -<a href="http://openjdk.java.net/jeps/150"><code>java.time</code></a> package, designed by the folks -behind the extremely capable Joda time library; <a href="http://openjdk.java.net/jeps/118">reflective -access</a> to parameter names; <a href="http://openjdk.java.net/jeps/133">Unicode -6.2</a> support; numerous others. But all of -these things are dwarfed by the “one last thing”:</p> -<p><strong>Lambdas</strong>.</p> -<h2 id="ok-so">Ok, So..?</h2> -<p>Here's the thing: all of the “modern” languages that see regular use - C#, -Python, Ruby, the various Lisps including Clojure, and Javascript - have -language features allowing easy creation and use of one-method values. In -Python, that's any object with a <code>__call__</code> method (including function -objects); in Ruby, it's blocks; in Javascript, it's <code>function() {}</code>s. These -features allow <em>computation itself</em> to be treated as a value and passed -around, which in turn provides a very powerful and succinct mechanism for -composing features.</p> -<p>Java's had the “use” side down for a long time; interfaces like <code>Runnable</code> are -a great example of ways to expose “function-like” or “procedure-like” types to -the language without violating Java's bureaucratic attitude towards types and -objects. However, the syntax for creating these one-method values has always -been so verbose and awkward as to discourage their use. Consider, for example, -a simple “task” for a thread pool:</p> -<pre><code>pool.execute(new Runnable() { - @Override - public void run() { - System.out.println("Hello, world!"); - } -}); -</code></pre> -<p>(Sure, it's a dumb example.)</p> -<p>Even leaving out the optional-but-recommended <code>@Override</code> annotation, that's -still five lines of code that only exist to describe to the compiler how to -package up a block as an object. Yuck. For more sophisticated tasks, this sort -of verbosity has lead to multi-role “event handler” interfaces, to amortize -the syntactic cost across more blocks of code.</p> -<p>With Java 8's lambda support, the same (dumb) example collapses to</p> -<pre><code>pool.execute(() -> System.out.println("Hello, world")); -</code></pre> -<p>It's the same structure and is implemented very similarly by the compiler. -However, it's got much greater informational density for programmers reading -the code, and it's much more pleasant to write.</p> -<p>If there's any justice, this will completely change how people design Java -software.</p> -<h2 id="event-driven-systems">Event-Driven Systems</h2> -<p>As an example, I knocked together a simple “event driven IO” system in an -evening, loosely inspired by node.js. Here's the echo server I wrote as an -example application, in its entirety:</p> -<pre><code>package com.example.onepointeight; - -import java.io.IOException; - -public class Echo { - public static void main(String[] args) throws IOException { - Reactor.run(reactor -> - reactor.listen(3000, client -> - reactor.read(client, data -> { - data.flip(); - reactor.write(client, data); - }) - ) - ); - } -} -</code></pre> -<p>It's got a bad case of Javascript “arrow” disease, but it demonstrates the -expressive power of lambdas for callbacks. This is built on NIO, and runs in a -single thread; as with any decent multiplexed-IO application, it starts to -have capacity problems due to memory exhaustion well before it starts to -struggle with the number of clients. Unlike Java 7 and earlier, though, the -whole program is short enough to keep in your head without worrying about the -details of how each callback is converted into an object and without having to -define three or four extra one-method classes.</p> -<h2 id="contextual-operations">Contextual operations</h2> -<p>Sure, we all know you use <code>try/finally</code> (or, if you're up on your Java 7, -<code>try()</code>) to clean things up. However, context isn't always as tidy as that: -sometimes things need to happen while it's set up, and un-happen when it's -being torn down. The folks behind JdbcTemplate already understood that, so you -can already write SQL operations using a syntax similar to</p> -<pre><code>User user = connection.query( - "SELECT login, group FROM users WHERE username = ?", - username, - rows -> rows.one(User::fromRow) -); -</code></pre> -<p>Terser <strong>and</strong> clearer than the corresponding try-with-resources version:</p> -<pre><code>try (PreparedStatement ps = connection.prepare("SELECT login, group FROM users WHERE username = ?")) { - ps.setString(1, username); - try (ResultSet rows = rs.execute()) { - if (!rows.next()) - throw new NoResultFoundException(); - return User.fromRow(rows); - } -} -</code></pre> -<h2 id="domain-specific-languages">Domain-Specific Languages</h2> -<p>I haven't worked this one out, yet, but I think it's possible to use lambdas -to implement conversational interfaces, similar in structure to “fluent” -interfaces like -<a href="http://docs.oracle.com/javaee/6/api/javax/ws/rs/core/UriBuilder.html">UriBuilder</a>. -If I can work out the mechanics, I'll put together an example for this, but -I'm half convinced something like</p> -<pre><code>URI googleIt = Uris.create(() -> { - scheme("http"); - host("google.com"); - path("/"); - queryParam("q", "hello world"); -}); -</code></pre> -<p>is possible.</p> - </div> - - - -<div id="comments"> -<div id="disqus_thread"></div> -<script type="text/javascript"> - /* * * CONFIGURATION VARIABLES: EDIT BEFORE PASTING INTO YOUR WEBPAGE * * */ - var disqus_shortname = 'grimoire'; // required: replace example with your forum shortname - - /* * * DON'T EDIT BELOW THIS LINE * * */ - (function() { - var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true; - dsq.src = 'http://' + disqus_shortname + '.disqus.com/embed.js'; - (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq); - })(); -</script> -<noscript>Please enable JavaScript to view the <a href="http://disqus.com/?ref_noscript">comments powered by Disqus.</a></noscript> -<a href="http://disqus.com" class="dsq-brlink">comments powered by <span class="logo-disqus">Disqus</span></a> -</div> - - - - <div id="footer"> - <p> - - The Codex — - - Powered by <a href="http://markdoc.org/">Markdoc</a>. - -<a href="https://bitbucket.org/ojacobson/grimoire.ca/src/master/wiki/java/a-new-kind-of.md">See this page on Bitbucket</a> (<a href="https://bitbucket.org/ojacobson/grimoire.ca/history-node/master/wiki/java/a-new-kind-of.md">history</a>). - - </p> - </div> - -</div> -</body> -</html>
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