bug #760014: autogenerate check documentation for duplicate code from javadoc
merged the existing texts in old config_duplicates.xml to package.html and java class doc
This commit is contained in:
Lars Kühne
parent
da1cb4309e
commit
08d574454c
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@ -29,23 +29,73 @@ import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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/**
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* Checks for duplicate code that only differs by indentation.
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* <p>
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* Performs a line-by-line comparison of all code lines and reports
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* duplicate code if a sequence of lines differs only in
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* indentation. All import statements in Java code are ignored, any
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* other line - including javadoc, whitespace lines between methods,
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* etc. - is considered (which is why the check is called
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* <em>strict</em>).
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* </p>
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*
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* <subsection name="Properties">
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* <table>
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* <tr>
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* <th>name</th>
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* <th>description</th>
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* <th>type</th>
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* <th>default value</th>
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* </tr>
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* <tr>
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* <td>min</td>
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* <td>how many lines must be equal to be considered a duplicate</td>
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* <td><a href="property_types.html#int">int</a></td>
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* <td><span class="default">12</span></td>
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* </tr>
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* <tr>
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* <td>charset</td>
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* <td>name of the file charset</td>
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* <td><a href="property_types.html#string">String</a></td>
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* <td>System property "file.encoding"</td>
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* </tr>
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* </table>
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* </subsection>
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*
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* <subsection name="Examples">
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* <p> To configure the check: </p>
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* <source>
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* <module name="StrictDuplicateCode"/>
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* </source>
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*
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* <p>
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* There are many approaches for detecting duplicate code. Some involve
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* parsing a file of a programming language and analyzing the source trees
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* of all files. This is a very powerful approach for a specific programming
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* language (such as Java), as it can potentially even detect duplicate code
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* where linebreaks have been changed, variables have been renamed, etc.
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* To configure the check so that it allows larger equivalent blocks:
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* </p>
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* <source>
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* <module name="StrictDuplicateCode">
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* <property name="min" value="15"/>
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* </module>
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* </source>
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*
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* <p>
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* This copy and paste detection implementation works differently.
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* It cannot detect copy and paste code where the author deliberately
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* tries to hide his copy+paste action. Instead it focusses on the standard
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* corporate problem of reuse by copy and paste. Usually this leaves linebreaks
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* and variable names intact. Since we do not need to analyse a parse tree
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* our tool is not tied to a particular programming language.
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* To configure the check so that it handles files with the <span
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* class="code">UTF-8</span> charset:
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* </p>
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* <source>
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* <module name="StrictDuplicateCode">
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* <property name="charset" value="UTF-8"/>
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* </module>
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* </source>
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* </subsection>
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*
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* <subsection name="Package">
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* <p>com.puppycrawl.tools.checkstyle.checks.duplicates</p>
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* </subsection>
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*
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* <subsection name="Parent Module">
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* <p>
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* <a href="config.html#Checker">Checker</a>
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* </p>
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* </subsection>
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*
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* @author Lars Kühne
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*/
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@ -1,7 +1,7 @@
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<html>
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<body>
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<p>
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<span class="xdocspagetitle">Duplicate code detection</span> allows you to find
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<span class="xdocspagetitle">Duplicate code</span> detection allows you to find
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code that has been generated by Copy/Paste programming. Duplicate code typically
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leads to higher maintainance cost because bugs will need to be fixed twice,
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more code needs to be tested, etc.
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@ -28,16 +28,49 @@ Note that there are brilliant commercial implementations of duplicate code
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detection tools. One that is particularly noteworthy is
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<a href="http://www.redhillconsulting.com.au/products/simian/">Simian</a>
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from RedHill Consulting, Inc.
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</p>
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<p>
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Simian has managed to find a very good balance of the above tradeoffs.
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It is superior to the checks in this package in many repects.
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Simian is reasonably priced (free for noncommercial projects)
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and includes a Checkstyle plugin.
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</p>
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<p>
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The following table summarizes the characteristics of the available
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Checkstyle plugins for duplicate code detection:
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</p>
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<table>
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<tr>
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<th>Name</th>
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<th>Speed</th>
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<th>Memory Usage</th>
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<th>False Alarms</th>
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<th>Supported languages</th>
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<th>Fuzzy matches</th>
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</tr>
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<tr>
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<td>StrictDuplicateCode</td>
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<td>Medium</td>
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<td>Very Low</td>
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<td>Possible but very unlikely</td>
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<td>any language</td>
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<td>No</td>
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</tr>
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<tr>
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<td>Simian</td>
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<td>Very high</td>
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<td>Low</td>
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<td>Possible but very unlikely</td>
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<td>many languages, including Java and C/C++/C#</td>
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<td>Limited support</td>
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</tr>
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</table>
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<p>
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<strong>
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We encourage all users of Checkstyle to evaluate Simian as an
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alternative to the Checks we offer in our distribution.
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</strong>
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</p>
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</body>
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</html>
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@ -1,143 +0,0 @@
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<?xml version="1.0" encoding="ISO-8859-1"?>
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<document>
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<properties>
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<title>Duplicate Code</title>
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<author email="checkstyle-devel@lists.sourceforge.net">Checkstyle Development Team</author>
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</properties>
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<body>
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<p>
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There are many trade-offs when writing a duplicate code detection tool.
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Some of the conflicting goals are:
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<ul>
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<li>Fast</li>
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<li>Low memory usage</li>
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<li>Avoid false alarms</li>
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<li>Support multiple/arbitrary languages</li>
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<li>
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Support Fuzzy matches (comments, whitespace, linebreaks, variable
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renaming, etc.)
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</li>
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</ul>
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</p>
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<p>
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Note that there are brilliant commercial implementations of duplicate
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code detection tools. One that is particularly noteworthy is <a
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href="http://www.redhillconsulting.com.au/products/simian/">Simian</a>
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from RedHill Consulting, Inc.
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</p>
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<p>
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Simian is reasonably priced (free for noncommercial projects) and
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includes a Checkstyle plugin. We encourage all users of Checkstyle to
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evaluate Simian as an alternative to the Checks we offer in our
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distribution.
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</p>
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<p>
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The following table summarizes the characteristics of the available
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Checkstyle plugins for duplicate code detection:
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</p>
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<table>
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<tr>
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<th>Name</th>
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<th>Speed</th>
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<th>Memory Usage</th>
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<th>False Alarms</th>
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<th>Supported languages</th>
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<th>Fuzzy matches</th>
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</tr>
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<tr>
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<td>StrictDuplicateCode</td>
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<td>Medium</td>
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<td>Very Low</td>
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<td>Possible but very unlikely</td>
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<td>any language</td>
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<td>No</td>
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</tr>
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<tr>
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<td>Simian</td>
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<td>Very high</td>
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<td>Low</td>
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<td>Possible but very unlikely</td>
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<td>many languages, including Java and C/C++/C#</td>
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<td>Limited support</td>
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</tr>
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</table>
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<section name="StrictDuplicateCode">
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<p>
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Performs a line-by-line comparison of all code lines and reports
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duplicate code, i.e. a sequence of lines that differ only in
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indentation. All import statements in Java code are ignored, any
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other line - including javadoc, whitespace lines between methods,
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etc. - is considered (which is why the check is called
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<em>strict</em>).
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</p>
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<subsection name="Properties">
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<table>
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<tr>
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<th>name</th>
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<th>description</th>
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<th>type</th>
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<th>default value</th>
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</tr>
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<tr>
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<td>min</td>
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<td>how many lines must be equal to be considered a duplicate</td>
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<td><a href="property_types.html#int">int</a></td>
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<td><span class="default">12</span></td>
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</tr>
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<tr>
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<td>charset</td>
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<td>name of the file charset</td>
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<td><a href="property_types.html#string">String</a></td>
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<td>System property "file.encoding"</td>
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</tr>
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</table>
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</subsection>
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<subsection name="Examples">
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<p> To configure the check: </p>
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<source>
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<module name="StrictDuplicateCode"/>
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</source>
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<p>
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To configure the check so that it allows larger equivalent blocks:
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</p>
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<source>
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<module name="StrictDuplicateCode">
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<property name="min" value="15"/>
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</module>
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</source>
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<p>
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To configure the check so that it handles files with the <span
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class="code">UTF-8</span> charset:
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</p>
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<source>
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<module name="StrictDuplicateCode">
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<property name="charset" value="UTF-8"/>
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</module>
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</source>
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</subsection>
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<subsection name="Package">
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<p> com.puppycrawl.tools.checkstyle.checks.duplicates </p>
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</subsection>
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<subsection name="Parent Module">
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<p>
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<a href="config.html#checker">Checker</a>
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</p>
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</subsection>
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</section>
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</body>
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</document>
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