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  <div class="section" id="code-style">
<h1>Code Style<a class="headerlink" href="#code-style" title="Permalink to this headline">¶</a></h1>
<div class="section" id="general-code-conventions">
<h2>General Code Conventions<a class="headerlink" href="#general-code-conventions" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div><ul class="simple">
<li>The Cassandra project follows <a class="reference external" href="http://java.sun.com/docs/codeconv/html/CodeConvTOC.doc.html">Sun&#8217;s Java coding conventions</a> with an important exception: <code class="docutils literal"><span class="pre">{</span></code> and <code class="docutils literal"><span class="pre">}</span></code> are always placed on a new line</li>
</ul>
</div></blockquote>
</div>
<div class="section" id="exception-handling">
<h2>Exception handling<a class="headerlink" href="#exception-handling" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div><ul class="simple">
<li>Never ever write <code class="docutils literal"><span class="pre">catch</span> <span class="pre">(...)</span> <span class="pre">{}</span></code> or <code class="docutils literal"><span class="pre">catch</span> <span class="pre">(...)</span> <span class="pre">{</span> <span class="pre">logger.error()</span> <span class="pre">}</span></code> merely to satisfy Java&#8217;s compile-time exception checking. Always propagate the exception up or throw <code class="docutils literal"><span class="pre">RuntimeException</span></code> (or, if it &#8220;can&#8217;t happen,&#8221; <code class="docutils literal"><span class="pre">AssertionError</span></code>). This makes the exceptions visible to automated tests.</li>
<li>Avoid propagating up checked exceptions that no caller handles. Rethrow as <code class="docutils literal"><span class="pre">RuntimeException</span></code> (or <code class="docutils literal"><span class="pre">IOError</span></code>, if that is more applicable).</li>
<li>Similarly, logger.warn() is often a cop-out: is this an error or not? If it is don&#8217;t hide it behind a warn; if it isn&#8217;t, no need for the warning.</li>
<li>If you genuinely know an exception indicates an expected condition, it&#8217;s okay to ignore it BUT this must be explicitly explained in a comment.</li>
</ul>
</div></blockquote>
</div>
<div class="section" id="boilerplate">
<h2>Boilerplate<a class="headerlink" href="#boilerplate" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div><ul class="simple">
<li>Avoid redundant <code class="docutils literal"><span class="pre">&#64;Override</span></code> annotations when implementing abstract or interface methods.</li>
<li>Do not implement equals or hashcode methods unless they are actually needed.</li>
<li>Prefer public final fields to private fields with getters. (But prefer encapsulating behavior in &#8220;real&#8221; methods to either.)</li>
<li>Prefer requiring initialization in the constructor to setters.</li>
<li>Avoid redundant <code class="docutils literal"><span class="pre">this</span></code> references to member fields or methods.</li>
<li>Do not extract interfaces (or abstract classes) unless you actually need multiple implementations of it.</li>
<li>Always include braces for nested levels of conditionals and loops. Only avoid braces for single level.</li>
</ul>
</div></blockquote>
</div>
<div class="section" id="multiline-statements">
<h2>Multiline statements<a class="headerlink" href="#multiline-statements" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div><ul class="simple">
<li>Try to keep lines under 120 characters, but use good judgement &#8211; it&#8217;s better to exceed 120 by a little, than split a line that has no natural splitting points.</li>
<li>When splitting inside a method call, use one line per parameter and align them, like this:</li>
</ul>
<div class="highlight-none"><div class="highlight"><pre><span></span>SSTableWriter writer = new SSTableWriter(cfs.getTempSSTablePath(),
                                         columnFamilies.size(),
                                         StorageService.getPartitioner());
</pre></div>
</div>
<ul class="simple">
<li>When splitting a ternary, use one line per clause, carry the operator, and align like this:</li>
</ul>
<div class="highlight-none"><div class="highlight"><pre><span></span>var = bar == null
    ? doFoo()
    : doBar();
</pre></div>
</div>
</div></blockquote>
</div>
<div class="section" id="whitespace">
<h2>Whitespace<a class="headerlink" href="#whitespace" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div><ul class="simple">
<li>Please make sure to use 4 spaces instead of the tab character for all your indentation.</li>
<li>Many lines in many files have a bunch of trailing whitespace... Please either clean these up in a separate patch, or leave them alone, so that reviewers now and anyone reading code history later doesn&#8217;t have to pay attention to whitespace diffs.</li>
</ul>
</div></blockquote>
</div>
<div class="section" id="imports">
<h2>Imports<a class="headerlink" href="#imports" title="Permalink to this headline">¶</a></h2>
<p>Please observe the following order for your imports:</p>
<div class="highlight-none"><div class="highlight"><pre><span></span>java
[blank line]
com.google.common
org.apache.commons
org.junit
org.slf4j
[blank line]
everything else alphabetically
</pre></div>
</div>
</div>
<div class="section" id="format-files-for-ides">
<h2>Format files for IDEs<a class="headerlink" href="#format-files-for-ides" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div><ul class="simple">
<li>IntelliJ: <a class="reference external" href="https://wiki.apache.org/cassandra/CodeStyle?action=AttachFile&amp;do=view&amp;target=intellij-codestyle.jar">intellij-codestyle.jar</a></li>
<li>IntelliJ 13: <a class="reference external" href="https://gist.github.com/jdsumsion/9ab750a05c2a567c6afc">gist for IntelliJ 13</a> (this is a work in progress, still working on javadoc, ternary style, line continuations, etc)</li>
<li>Eclipse (<a class="reference external" href="https://github.com/tjake/cassandra-style-eclipse">https://github.com/tjake/cassandra-style-eclipse</a>)</li>
</ul>
</div></blockquote>
</div>
</div>


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