Home > Articles > Programming > Windows Programming

Robert C. Martin's Clean Code Tip of the Week #6: Avoid Poorly Written Comments

We join "The Craftsman," Robert C. Martin's series on an interstellar spacecraft where programmers hone their coding skills. In this sixth tip in the series, the crewmen try to interpret a poorly worded comment.
You can review additional articles from Robert C. Martin's series, "The Craftsman," on the ObjectMentor website.
Like this article? We recommend

Mar 10, 1945, 12:00:00 GMT

The worst of the Anthrax attack was over. More than twenty thousand people were dead, and many more lay sick and dying, but the quarantine orders put in place by president Wallace at the recommendation of Jonas Salk, had stopped the spread of the disease. The government was literally decimated. Congress had lost one in eight. The White House had lost one in ten.Worse yet, the Nimbus project had lost a full third of its scientists and workers. The military was still trying to count its dead.

“Hitler’s agents have been in the country for years.” J. Edgar. Hoover said to Wallace. “This attack was very carefully planned and executed. Infectious agents were released over a period of several days in locations known to be frequented by government personnel. Mr. President, we cannot let this go unanswered.”

“We won’t John.” Wallace turned to Patton and DoLittle. “Gentlemen, what do you recommend?”

The two generals looked at each other and Patton, speaking around his cigar, responded. “Sir, an single Orion vessel could fly over Europe and Asia and drop thousands of atomic weapons on them day after day. After a week there’d be nothing left of the whole stinking continent. No city larger than 3,000 would be left standing.” He took the cigar out of his mouth and gazed at the glowing coal. “The second vessel is nearly ready.” He looked up with a grin. “We rather like the name: Raptor. Three thousand of the kiloton bombs we use for propellant will be weapon-ized and ruggedized to survive the trip back into the air. Give us 6 weeks and we’ll be ready.” Patton once again clenched the cigar between his teeth and stared defiantly at his commander-in-chief.

Dolittle squirmed in his chair. “But sir,” he said. “What we don’t understand is why they didn’t mount a land invasion during all the confusion here. They could have walked right in here. I mean by all rights, they should be sitting here now instead of us.”

Monday, 12 Mar 2002, 09:00

“Hey, Avery, can I borrow you for a minute?”

Avery glared at me for a second, as though the weight of the ship were on his shoulders. Then he slowly got up and sat down next to me.

“What is it now?” he asked.  Sometimes Avery’s moods are tough to handle.

“Look at this code for a second, will you?” And I pointed at the screen.


  * Creates a relative url by stripping the common parts of the the url.


  * @param url    the to be stripped url

  * @param baseURL the base url, to which the <code>url</code>

is relative

  *               to.

  * @return the relative url, or the url unchanged, if there is no

  *         beween both URLs.


 public static String createRelativeURL(final URL url, final URL baseURL)

    boolean sameProtocol = url.getProtocol().equals(baseURL.getProtocol());

    boolean sameHost = url.getHost().equals(baseURL.getHost());

    boolean samePort = url.getPort() == baseURL.getPort();

    if (sameProtocol && sameHost &&samePort) {


      // If the URL contains a query, ignore that URL; do not

      // attemp to modify it...

      List urlName = parseName(getPath(url));

      List baseName = parseName(getPath(baseURL));

      String query = getQuery(url);


      if (!isPath(baseURL)) {

       baseName.remove(baseName.size() - 1);



      // if both urls are identical, then
return the plain file name...

      if (url.equals(baseURL)) {

        return (String)urlName.get(urlName.size() - 1);



      int commonIndex = startsWithUntil(urlName, baseName);

      if (commonIndex == 0) {

        return url.toExternalForm();



      if (commonIndex == urlName.size()) {

        // correct the base index if there is some weird mapping

        // detected,

        // fi. the file url is fully included in the base url:


        // base: /file/test/funnybase

        // file: /file/test


        // this could be a valid configuration whereever virtual

        // mappings are allowed.

        commonIndex -= 1;



      final ArrayList retval = new ArrayList();

      if (baseName.size() >= urlName.size()) {

        final int levels = baseName.size() - commonIndex;

        for (int i = 0; i < levels; i++) {





     retval.addAll(urlName.subList(commonIndex, urlName.size()));

      return formatName(retval, query);


    return url.toExternalForm();


“Who wrote this smut?” Avery proclaimed after looking through it for a few seconds.

“I don’t know.” I said. “I found it buried in this old application I’m trying to learn.”

Avery grimaced. “Where are the tests?”

“Yeah, about that…” I grinned knowingly.

Avery rolled his eyes and took on a disgusted demeanor.“OK, so there aren ’t any tests.”

“None that came with the code, but I’ve written a couple so far.”

“Good, let’s see them.”  Avery commanded. So I waved a new screen into existence.

public class UrlToolTest {


 public void canCreateSimpleRelativeUrl() throws Exception {

    URL base = new URL("http://www.alphonse.net/alpha/");

    URL full =  new URL("http://www.alphonse.net/alpha/beta");

    String relativeUrl = UrlTool.createRelativeURL(full, base);

    assertEquals("beta", relativeUrl);




 public void canHandleBackwardsReference() throws Exception {

    URL base = new URL("http://www.alphonse.net/alpha/beta/");

    URL full = new URL("http://www.alphonse.net/alpha");

    String relativeUrl = UrlTool.createRelativeURL(full, base);

    assertEquals("../../alpha", relativeUrl);



Avery looked a these for a few more seconds and then proclaimed: “Oh, I see, given two URLs it just figures out how to make one relative to the other.”

“I think that’s right”, I said.

“OK, so why’d you call me over here?”

I pointed to the multi-line comment in the middle of the module and said: “I don’t understand that comment.”

“Who reads comments?” Avery said with a sneer. Then he looked closer.  “Yeah, it’s not really a literary masterpiece is it? … I mean really.” And then he glared at the screen for a second and pointed to the fi In the midst of the comment. “Fie? Fie? What the hell does Fie mean? Fee, Fie, Fo, Fum. Fie?” And he looked at me with this big silly incredulous grin on his face.

“Fie?” I asked.

“Fie!” Avery declared with enthusiasm.

“Could it mean: ‘for instance’?” I asked.

“No!, it means Fie! FIE! Damn you!”

I could see this was degrading rapidly. “OK, I agree. Fie! But what the heck is he talking about in the rest of the comment”?

“Who the hell knows.” Avery said, and then he looked closer. “I suppose that the “base index” must be the commonIndex variable.”

“Maybe, though you’d think he’d have named the variable baseIndex in that case?”

“Maybe he did once, but then he changed the name of the variable.  Who knows?”

“Do you know what he means by ‘virtual mapping’?”

“God no. Is that a mapping that has virtue? Or a mapping that doesn’t exist? Or a mapping that’s just weird, like he says a few lines above? Who knows? I’m not even sure I know what he means by the term ‘mapping’, let alone ‘virtual mapping’.”

“And then what’s all this stuff about ‘configurations’? Configurations of what?”

Avery paused for a second and then shook his head. “Hell, Alphonse, why are you trying to understand this? The author couldn’t even take the time to spell a word like ‘wherever’ correctly. So he clearly isn’t interested in communicating. He was probably guilty about the mess he’d made in this function, so we wrote a perfunctory comment and then just walked away.”

Then Avery jabbed his finger in the air and said: “Alphonse, I have the solution. I know what to do.”

“You do?”

“Yes, I do.” And he waved at the screen and deleted the comment.  I had my sound effects set to make a popping noise for deletes. It was a very satisfying sound in this case.

“There.” Said Avery. “Problem solved.” And he went back and sat down at his workstation.

I pondered his solution for a moment, and realized he was probably right. That comment told me nothing useful at all. It may have meant something to the author at one time, but the author was clearly not trying to communicate with me.

I waved open the Clean Code heuristics and saw:

C4: Poorly Written Comment

A comment worth writing is worth writing well. If you are going to write a comment, take the time to make sure it is the best comment you can write. Choose your words carefully. Use correct grammar and punctuation. Don’t ramble. Don’t state the obvious. Be brief.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020