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<div id="updated">Updated: 2025-08-28 Thu 16:52</div>
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<div id="content" class="content">
<h1 class="title">Clean Code: Chapter 4 Notes</h1>
<div class="filetags"><a href="/categories.html"> <span class="post-tag">books</span> </a> <a href="/categories.html"> <span class="post-tag">notes</span> </a></div>
<div id="table-of-contents" role="doc-toc">
<h2>Table of Contents</h2>
<div id="text-table-of-contents" role="doc-toc">
<ul>
<li><a href="#org654cde4">Chapter 4: Comments</a>
<ul>
<li><a href="#orga48d099">Comments Do Not Make Up for Bad Code</a></li>
<li><a href="#org8a9af22">Good Comments</a>
<ul>
<li><a href="#orga00e43a">Legal Comments</a></li>
<li><a href="#org5d052d2">Informative Comments</a></li>
<li><a href="#orgc07d869">Explanation of Intent</a></li>
<li><a href="#orgeac0874">Clarification</a></li>
<li><a href="#org925a6b4">Warning of Consequences</a></li>
<li><a href="#org3c48674"><span class="todo TODO">TODO</span> Comments</a></li>
<li><a href="#org40776a2">Amplification</a></li>
<li><a href="#orga01f4c8">Javadocs in Public APIs</a></li>
</ul>
</li>
<li><a href="#orgdf9d0a0">Bad Comments</a>
<ul>
<li><a href="#org513ee74">Dont Use a Comment When You Can Use a Function or Variable</a></li>
<li><a href="#org47d711f">Position Markers</a></li>
<li><a href="#org166362e">Closing Brace Comments</a></li>
<li><a href="#orga7d0949">Attributions and Bylines</a></li>
<li><a href="#org087890b">Commented Out Code</a></li>
<li><a href="#org2707e8f">HTML Comments</a></li>
<li><a href="#orgd3ef1af">Nonlocal Information</a></li>
<li><a href="#org6859e2c">Too Much Information</a></li>
<li><a href="#orgd7d19c8">Inobvious Connection</a></li>
<li><a href="#org24f323a">Function Headers</a></li>
<li><a href="#orgd626f64">Javadocs in Nonpublic Code</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
</div>
<p>
Link to <a href="clean-code-chapter-3.html">Chapter 3</a> | Link to <a href="clean-code-chapter-5.html">Chapter 5</a>
</p>
<div id="outline-container-org654cde4" class="outline-2">
<h2 id="org654cde4">Chapter 4: Comments</h2>
<div class="outline-text-2" id="text-org654cde4">
<p>
Comments are a necessary evil—they exist because code fails to express intent clearly.
</p>
<p>
Outdated comments are dangerous; they can mislead more than help.
</p>
<p>
Strive to write code that explains itself; comments should be minimised.
</p>
<p>
Truth is always in the code, not in the comments.
</p>
</div>
<div id="outline-container-orga48d099" class="outline-3">
<h3 id="orga48d099">Comments Do Not Make Up for Bad Code</h3>
<div class="outline-text-3" id="text-orga48d099">
<p>
Dont use comments to excuse messy, unclear code. Clean the code instead.
</p>
<p>
Clear, expressive code with few comments &gt; cluttered code with many comments.
</p>
<div class="org-src-container">
<pre class="src src-java">
<span class="org-comment-delimiter">// </span><span class="org-comment">Check to see if the employee is eligible for full benefits
</span><span class="org-keyword">if</span> ((employee.flags &amp; HOURLY_FLAG) &amp;&amp; (employee.age &gt; 65))
<span class="org-comment-delimiter">// </span><span class="org-comment">Better:
</span><span class="org-keyword">if</span> (employee.isEligibleForFullBenefits())
</pre>
</div>
</div>
</div>
<div id="outline-container-org8a9af22" class="outline-3">
<h3 id="org8a9af22">Good Comments</h3>
<div class="outline-text-3" id="text-org8a9af22">
<p>
Only write them when unavoidable. Such as in the following instances:
</p>
</div>
<div id="outline-container-orga00e43a" class="outline-4">
<h4 id="orga00e43a">Legal Comments</h4>
<div class="outline-text-4" id="text-orga00e43a">
<p>
Sometimes required for copyright/licensing.
</p>
<p>
Keep them short; refer to standard licenses rather than embedding full legal text.
</p>
</div>
</div>
<div id="outline-container-org5d052d2" class="outline-4">
<h4 id="org5d052d2">Informative Comments</h4>
<div class="outline-text-4" id="text-org5d052d2">
<p>
Explain return values, formats, or patterns.
</p>
<p>
Prefer naming/structuring code to make such comments unnecessary.
</p>
<div class="org-src-container">
<pre class="src src-java">
<span class="org-comment-delimiter">// </span><span class="org-comment">format matched kk:mm:ss EEE, MMM dd, yyyy
</span><span class="org-type">Pattern</span> <span class="org-variable-name">timeMatcher</span> = Pattern.compile(<span class="org-string">"\\d*:\\d*:\\d* \\w*, \\w* \\d*, \\d*"</span>);
</pre>
</div>
</div>
</div>
<div id="outline-container-orgc07d869" class="outline-4">
<h4 id="orgc07d869">Explanation of Intent</h4>
<div class="outline-text-4" id="text-orgc07d869">
<p>
Describe why a certain approach was chosen.
</p>
<p>
Helps future maintainers understand reasoning behind code.
</p>
<div class="org-src-container">
<pre class="src src-java">
<span class="org-keyword">public</span> <span class="org-type">int</span> <span class="org-function-name">compareTo</span>(<span class="org-type">Object</span> <span class="org-variable-name">o</span>)
{
<span class="org-keyword">if</span>(o <span class="org-keyword">instanceof</span> WikiPagePath)
{ <span class="org-type">WikiPagePath</span> <span class="org-variable-name">p</span> = (<span class="org-type">WikiPagePath</span>) o;
<span class="org-type">String</span> <span class="org-variable-name">compressedName</span> = StringUtil.join(names, <span class="org-string">""</span>);
<span class="org-type">String</span> <span class="org-variable-name">compressedArgumentName</span> = StringUtil.join(p.names, <span class="org-string">""</span>);
<span class="org-keyword">return</span> compressedName.compareTo(compressedArgumentName);
}
<span class="org-keyword">return</span> 1; <span class="org-comment-delimiter">// </span><span class="org-comment">we are greater because we are the right type.
</span>}
</pre>
</div>
</div>
</div>
<div id="outline-container-orgeac0874" class="outline-4">
<h4 id="orgeac0874">Clarification</h4>
<div class="outline-text-4" id="text-orgeac0874">
<p>
Translate obscure values into readable terms.
</p>
<p>
Useful when working with unchangeable APIs/libraries, but risky if incorrect.
</p>
</div>
</div>
<div id="outline-container-org925a6b4" class="outline-4">
<h4 id="org925a6b4">Warning of Consequences</h4>
<div class="outline-text-4" id="text-org925a6b4">
<p>
Alert others about performance, thread-safety, or side effects.
</p>
<p>
For example, in code you can say:
</p>
<p>
<code>// SimpleDateFormat is not thread safe, so create each instance independently.</code>
</p>
</div>
</div>
<div id="outline-container-org3c48674" class="outline-4">
<h4 id="org3c48674"><span class="todo TODO">TODO</span> Comments</h4>
<div class="outline-text-4" id="text-org3c48674">
<p>
Mark incomplete work or planned improvements.
</p>
<p>
Should be reviewed regularly; not an excuse for bad code.
</p>
</div>
</div>
<div id="outline-container-org40776a2" class="outline-4">
<h4 id="org40776a2">Amplification</h4>
<div class="outline-text-4" id="text-org40776a2">
<p>
Highlight the importance of seemingly small details.
</p>
<p>
<code>// the trim is real important. It removes starting spaces...</code>
</p>
</div>
</div>
<div id="outline-container-orga01f4c8" class="outline-4">
<h4 id="orga01f4c8">Javadocs in Public APIs</h4>
<div class="outline-text-4" id="text-orga01f4c8">
<p>
Public APIs should have clear documentation.
</p>
<p>
Javadocs can also mislead. Keep them accurate and up-to-date.
</p>
</div>
</div>
</div>
<div id="outline-container-orgdf9d0a0" class="outline-3">
<h3 id="orgdf9d0a0">Bad Comments</h3>
<div class="outline-text-3" id="text-orgdf9d0a0">
<ul class="org-ul">
<li>Don't place a comment just because you feel like it.</li>
<li>Remove redundant comments.</li>
<li>Avoid misleading comments.</li>
<li>Don't mandate everything (not every function needs a Javadoc).</li>
<li>No need for journal comments, we have source control.</li>
<li>Remove noise comments.</li>
</ul>
</div>
<div id="outline-container-org513ee74" class="outline-4">
<h4 id="org513ee74">Dont Use a Comment When You Can Use a Function or Variable</h4>
<div class="outline-text-4" id="text-org513ee74">
<p>
Replace explanatory comments with expressive variable or function names.
</p>
<p>
Refactor code to remove comment redundancy.
</p>
</div>
</div>
<div id="outline-container-org47d711f" class="outline-4">
<h4 id="org47d711f">Position Markers</h4>
<div class="outline-text-4" id="text-org47d711f">
<p>
Avoid decorative banners like <code>// Actions ///////////////////////</code>, they add clutter.
</p>
<p>
Use sparingly and only for meaningful grouping.
</p>
<p>
Overuse makes them blend into background noise.
</p>
</div>
</div>
<div id="outline-container-org166362e" class="outline-4">
<h4 id="org166362e">Closing Brace Comments</h4>
<div class="outline-text-4" id="text-org166362e">
<p>
Comments on closing braces (} // while) are unnecessary for small, well structured functions.
</p>
<p>
Prefer short, clear functions over brace markers.
</p>
</div>
</div>
<div id="outline-container-orga7d0949" class="outline-4">
<h4 id="orga7d0949">Attributions and Bylines</h4>
<div class="outline-text-4" id="text-orga7d0949">
<p>
Dont add personal tags like <code>/* Added by Rick */</code>, use version control for authorship history.
</p>
<p>
Such comments become outdated and irrelevant over time.
</p>
</div>
</div>
<div id="outline-container-org087890b" class="outline-4">
<h4 id="org087890b">Commented Out Code</h4>
<div class="outline-text-4" id="text-org087890b">
<p>
Never keep old code commented out; delete it and rely on version control history.
</p>
<p>
Commented-out code adds clutter and confuses future maintainers.
</p>
<div class="org-src-container">
<pre class="src src-java">
<span class="org-comment-delimiter">// </span><span class="org-comment">Old cruft that should be deleted:
</span><span class="org-comment-delimiter">//</span><span class="org-comment">hdrPos = bytePos;
</span><span class="org-comment-delimiter">//</span><span class="org-comment">dataPos = bytePos;
</span>
</pre>
</div>
</div>
</div>
<div id="outline-container-org2707e8f" class="outline-4">
<h4 id="org2707e8f">HTML Comments</h4>
<div class="outline-text-4" id="text-org2707e8f">
<p>
Avoid HTML markup inside code comments, it makes them harder to read in the editor.
</p>
<p>
Let documentation tools (like Javadoc) handle formatting.
</p>
</div>
</div>
<div id="outline-container-orgd3ef1af" class="outline-4">
<h4 id="orgd3ef1af">Nonlocal Information</h4>
<div class="outline-text-4" id="text-orgd3ef1af">
<p>
Comments should describe nearby code only, not unrelated parts of the system.
</p>
<p>
Avoid embedding global/system details that the function cant control.
</p>
</div>
</div>
<div id="outline-container-org6859e2c" class="outline-4">
<h4 id="org6859e2c">Too Much Information</h4>
<div class="outline-text-4" id="text-org6859e2c">
<p>
Avoid long, unnecessary historical or technical explanations.
</p>
<p>
Keep only relevant context (e.g., “RFC 2045” reference is fine, not the full spec).
</p>
</div>
</div>
<div id="outline-container-orgd7d19c8" class="outline-4">
<h4 id="orgd7d19c8">Inobvious Connection</h4>
<div class="outline-text-4" id="text-orgd7d19c8">
<p>
Ensure the relationship between comment and code is clear.
</p>
<p>
Dont make readers guess what part of the code the comment refers to.
</p>
<div class="org-src-container">
<pre class="src src-java">
<span class="org-comment-delimiter">// </span><span class="org-comment">plus filter bytes ... but which part is &#8220;filter&#8221;?
</span><span class="org-keyword">this</span>.pngBytes = <span class="org-keyword">new</span> <span class="org-type">byte</span>[((<span class="org-keyword">this</span>.width + 1) * <span class="org-keyword">this</span>.height * 3) + 200];
</pre>
</div>
</div>
</div>
<div id="outline-container-org24f323a" class="outline-4">
<h4 id="org24f323a">Function Headers</h4>
<div class="outline-text-4" id="text-org24f323a">
<p>
Short, single purpose functions with good names dont need header comments.
</p>
<p>
Let the function name explain the purpose.
</p>
</div>
</div>
<div id="outline-container-orgd626f64" class="outline-4">
<h4 id="orgd626f64">Javadocs in Nonpublic Code</h4>
<div class="outline-text-4" id="text-orgd626f64">
<p>
Javadocs are useful for public APIs, but excessive formality in internal code is just noise.
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Internal methods should be self explanatory without full doc comments.
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