checkstyle/src/xdocs/config_misc.xml

1745 lines
58 KiB
XML
Executable File

<?xml version="1.0" encoding="UTF-8"?>
<document xmlns="http://maven.apache.org/XDOC/2.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">
<properties>
<title>Miscellaneous</title>
<author>Checkstyle Development Team</author>
</properties>
<body>
<section name="NewlineAtEndOfFile">
<subsection name="Description">
<p>
Checks whether files end with a line separator.
</p>
<p>
Rationale: Any source files and text files in general should
end with a line separator, especially when using source control management
systems such as CVS. CVS will even print a warning when it
encounters a file that doesn't end with a line separator.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>lineSeparator</td>
<td>type of line separator</td>
<td>
One of &quot;system&quot; (system default),
&quot;crlf&quot; (Windows-style), &quot;cr&quot;
(Mac-style) and &quot;lf&quot; (Unix-style)
</td>
<td>&quot;system&quot;</td>
</tr>
<tr>
<td>fileExtensions</td>
<td>file type extension of the files to check.</td>
<td><a href="property_types.html#stringSet">String Set</a></td>
<td>all files</td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;NewlineAtEndOfFile&quot;/&gt;
</source>
<p>
To configure the check to always use Unix-style line separators:
</p>
<source>
&lt;module name=&quot;NewlineAtEndOfFile&quot;&gt;
&lt;property name=&quot;lineSeparator&quot; value=&quot;lf&quot;/&gt;
&lt;/module&gt;
</source>
<p>
To configure the check to work only on Java, XML and Python files:
</p>
<source>
&lt;module name=&quot;NewlineAtEndOfFile&quot;&gt;
&lt;property name=&quot;fileExtensions&quot; value=&quot;java, xml, py&quot;/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#Checker">Checker</a>
</p>
</subsection>
</section>
<section name="TodoComment">
<subsection name="Description">
<p>
A check for <code>TODO:</code> comments. Actually
it is a generic <a
href="https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html">regular
expression</a> matcher on Java comments. To check for other
patterns in Java comments, set the <code>format</code> property.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>format</td>
<td>Pattern to match comments against</td>
<td><a href="property_types.html#regexp">regular expression</a></td>
<td><code>TODO:</code></td>
</tr>
</table>
</subsection>
<subsection name="Notes">
<p>
Using <code>TODO:</code> comments is a great way
to keep track of tasks that need to be done. Having them
reported by Checkstyle makes it very hard to forget about
them.
</p>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;TodoComment&quot;/&gt;
</source>
<p>
To configure the check for comments that contain <code>WARNING</code>:
</p>
<source>
&lt;module name=&quot;TodoComment&quot;&gt;
&lt;property name=&quot;format&quot; value=&quot;WARNING&quot;/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="Translation">
<subsection name="Description">
<p>
A <a href="config.html#Overview">FileSetCheck</a> that ensures
the correct translation of code by checking property files for
consistency regarding their keys. Two property files
describing one and the same context are consistent if they
contain the same keys.
</p>
<p>
Consider the following properties file in the same directory:
</p>
<source>
#messages.properties
hello=Hello
cancel=Cancel
#messages_de.properties
hell=Hallo
ok=OK
</source>
<p>
The Translation check will find the typo in the German <code>hello</code>
key, the missing <code>ok</code> key in the default resource file and the
missing <code>cancel</code> key in the German resource file:
</p>
<source>
messages_de.properties: Key 'hello' missing.
messages_de.properties: Key 'cancel' missing.
messages.properties: Key 'hell' missing.
messages.properties: Key 'ok' missing.
</source>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>fileExtensions</td>
<td>
file type extension to identify translation files. Setting
this property is typically only required if your
translation files are preprocessed and the original files
do not have the extension <code>.properties</code>
</td>
<td><a href="property_types.html#stringSet">String Set</a></td>
<td><code>properties</code></td>
</tr>
<tr>
<td>basenameSeparator</td>
<td>Allows setting file names separator</td>
<td><a href="property_types.html#string">String</a></td>
<td><code>_</code></td>
</tr>
</table>
</subsection>
<subsection name="Example">
<p>
To configure the check for files with '_' name separator:
</p>
<source>
&lt;module name=&quot;Translation&quot;/&gt;
</source>
<p>
To configure the check for files with user-set name separator:
</p>
<source>
&lt;module name=&quot;Translation&quot;&gt;
&lt;property name=&quot;basenameSeparator&quot; value=&quot;STRING_LITERAL&quot;/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#Checker">Checker</a>
</p>
</subsection>
</section>
<section name="UncommentedMain">
<subsection name="Description">
<p>
Checks for uncommented main() methods.
</p>
<p>
Rationale: A main() method is often used for debugging
purposes. When debugging is finished, developers often forget
to remove the method, which changes the API and increases the
size of the resulting class or JAR file. With the exception of
the real program entry points, all main() methods should be
removed or commented out of the sources.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>excludedClasses</td>
<td>Pattern for qualified names of classes which are allowed
to have a main method.</td>
<td><a href="property_types.html#regexp">regular expression</a></td>
<td><code>^$</code></td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;UncommentedMain&quot;/&gt;
</source>
<p>
To configure the check to allow the <code>main</code> method for all classes
with &quot;Main&quot; name:
</p>
<source>
&lt;module name=&quot;UncommentedMain&quot;&gt;
&lt;property name=&quot;excludedClasses&quot; value=&quot;\.Main$&quot;/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="UpperEll">
<subsection name="Description">
<p>
Checks that long constants are defined with an upper ell. That
is <code>' L'</code> and not <code>'l'</code>. This is in accordance with the Java
Language Specification, <a
href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#48282">
Section 3.10.1</a>.
</p>
<p>
The capital L looks a lot like <code>1</code>.
</p>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;UpperEll&quot;/&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="ArrayTypeStyle">
<subsection name="Description">
<p>
Checks the style of array type definitions. Some like Java style:
<code>public static void main(String[] args)</code> and some like
C style: public static void main(String args[])
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>javaStyle</td>
<td>
Controls whether to enforce Java style (true) or C style (false).
</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td><code>true</code></td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
To configure the check to enforce Java style:
</p>
<source>
&lt;module name=&quot;ArrayTypeStyle&quot;/&gt;
</source>
<p>
To configure the check to enforce C style:
</p>
<source>
&lt;module name=&quot;ArrayTypeStyle&quot;&gt;
&lt;property name=&quot;javaStyle&quot; value=&quot;false&quot;/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="FinalParameters">
<subsection name="Description">
<p>
Check that parameters for methods, constructors, and catch blocks are
final. Interface and abstract methods are not checked: the final
keyword does not make sense for interface and abstract method
parameters as there is no code that could modify the parameter.
</p>
<p>
Rationale: Changing the value of parameters during the execution of
the method's algorithm can be confusing and should be avoided. A
great way to let the Java compiler prevent this coding style is to
declare parameters final.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>tokens</td>
<td>blocks to check</td>
<td>subset of tokens <a
href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_DEF">METHOD_DEF</a>,
<a
href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CTOR_DEF">CTOR_DEF</a>,
<a
href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#LITERAL_CATCH">LITERAL_CATCH</a></td>
<td><a
href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_DEF">METHOD_DEF</a>,
<a
href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CTOR_DEF">CTOR_DEF</a></td>
</tr>
<tr>
<td>ignorePrimitiveTypes</td>
<td>ignore primitive types as parameters</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td><code>false</code></td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
To configure the check to enforce final parameters for methods and
constructors:
</p>
<source>
&lt;module name=&quot;FinalParameters&quot;/&gt;
</source>
<p>
To configure the check to enforce final parameters only for
constructors:
</p>
<source>
&lt;module name=&quot;FinalParameters&quot;&gt;
&lt;property name=&quot;tokens&quot; value=&quot;CTOR_DEF&quot;/&gt;
&lt;/module&gt;
</source>
<p>
To configure the check to allow ignoring
<a href="http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html">
primitive datatypes</a> as parameters:
</p>
<source>
&lt;module name=&quot;FinalParameters&quot;&gt;
&lt;property name=&quot;ignorePrimitiveTypes&quot; value=&quot;true&quot;/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="DescendantToken">
<subsection name="Description">
<p>
Checks for restricted tokens beneath other tokens.
</p>
<p>
WARNING: This is a very powerful and flexible check, but, at the
same time, it is low-level and very implementation-dependent because
its results depend on the grammar we use to build abstract syntax
trees. Thus we recommend using other checks when they provide the
desired functionality. Essentially, this check just works on the level
of an abstract syntax tree and knows nothing about language structures.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>tokens</td>
<td>token types to check</td>
<td>subset of tokens declared in <a
href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html">TokenTypes</a></td>
<td>empty set</td>
</tr>
<tr>
<td>limitedTokens</td>
<td>set of tokens with limited occurrences as descendants</td>
<td>subset of tokens declared in <a
href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html">TokenTypes</a></td>
<td>empty set</td>
</tr>
<tr>
<td>minimumDepth</td>
<td>the minimum depth for descendant counts</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>0</td>
</tr>
<tr>
<td>maximumDepth</td>
<td>the maximum depth for descendant counts</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>java.lang.Integer.MAX_VALUE</td>
</tr>
<tr>
<td>minimumNumber</td>
<td>a minimum count for descendants</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>0</td>
</tr>
<tr>
<td>maximumNumber</td>
<td>a maximum count for descendants</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>java.lang.Integer.MAX_VALUE</td>
</tr>
<tr>
<td>sumTokenCounts</td>
<td>
whether the number of tokens found should be calculated
from the sum of the individual token counts
</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td><code>false</code></td>
</tr>
<tr>
<td>minimumMessage</td>
<td>error message when the minimum count is not reached</td>
<td><a href="property_types.html#string">String</a></td>
<td>&quot;descendant.token.min&quot;</td>
</tr>
<tr>
<td>maximumMessage</td>
<td>error message when the maximum count is exceeded</td>
<td><a href="property_types.html#string">String</a></td>
<td>&quot;descendant.token.max&quot;</td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
Comparing <code>this</code> with <code>null</code> (i.e. <code>this ==
null</code> and <code>this != null</code>):
</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="EQUAL,NOT_EQUAL"/&gt;
&lt;property name="limitedTokens" value="LITERAL_THIS,LITERAL_NULL"/&gt;
&lt;property name="maximumNumber" value="1"/&gt;
&lt;property name="maximumDepth" value="1"/&gt;
&lt;property name="sumTokenCounts" value="true"/&gt;
&lt;/module&gt;
</source>
<p>String literal equality check:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="EQUAL,NOT_EQUAL"/&gt;
&lt;property name="limitedTokens" value="STRING_LITERAL"/&gt;
&lt;property name="maximumNumber" value="0"/&gt;
&lt;property name="maximumDepth" value="1"/&gt;
&lt;/module&gt;
</source>
<p>Switch with no default:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="LITERAL_SWITCH"/&gt;
&lt;property name="maximumDepth" value="2"/&gt;
&lt;property name="limitedTokens" value="LITERAL_DEFAULT"/&gt;
&lt;property name="minimumNumber" value="1"/&gt;
&lt;/module&gt;
</source>
<p>
Assert statement may have side effects (formatted for browser
display):
</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="LITERAL_ASSERT"/&gt;
&lt;property name="limitedTokens" value="ASSIGN,DEC,INC,POST_DEC,
POST_INC,PLUS_ASSIGN,MINUS_ASSIGN,STAR_ASSIGN,DIV_ASSIGN,MOD_ASSIGN,
BSR_ASSIGN,SR_ASSIGN,SL_ASSIGN,BAND_ASSIGN,BXOR_ASSIGN,BOR_ASSIGN,
METHOD_CALL"/&gt;
&lt;property name="maximumNumber" value="0"/&gt;
&lt;/module&gt;
</source>
<p>
The initialiser in <code>for</code> performs no setup (where a <code>while</code> statement could be used instead):
</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="FOR_INIT"/&gt;
&lt;property name="limitedTokens" value="EXPR"/&gt;
&lt;property name="minimumNumber" value="1"/&gt;
&lt;/module&gt;
</source>
<p>
The condition in <code>for</code> performs no check:
</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="FOR_CONDITION"/&gt;
&lt;property name="limitedTokens" value="EXPR"/&gt;
&lt;property name="minimumNumber" value="1"/&gt;
&lt;/module&gt;
</source>
<p>
A switch within a switch:
</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="LITERAL_SWITCH"/&gt;
&lt;property name="limitedTokens" value="LITERAL_SWITCH"/&gt;
&lt;property name="maximumNumber" value="0"/&gt;
&lt;property name="minimumDepth" value="1"/&gt;
&lt;/module&gt;
</source>
<p>A return statement from within a catch or finally block:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="LITERAL_FINALLY,LITERAL_CATCH"/&gt;
&lt;property name="limitedTokens" value="LITERAL_RETURN"/&gt;
&lt;property name="maximumNumber" value="0"/&gt;
&lt;/module&gt;
</source>
<p>A try statement within a catch or finally block:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="LITERAL_CATCH,LITERAL_FINALLY"/&gt;
&lt;property name="limitedTokens" value="LITERAL_TRY"/&gt;
&lt;property name="maximumNumber" value="0"/&gt;
&lt;/module&gt;
</source>
<p>Too many cases within a switch:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="LITERAL_SWITCH"/&gt;
&lt;property name="limitedTokens" value="LITERAL_CASE"/&gt;
&lt;property name="maximumDepth" value="2"/&gt;
&lt;property name="maximumNumber" value="10"/&gt;
&lt;/module&gt;
</source>
<p>Too many local variables within a method:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="METHOD_DEF"/&gt;
&lt;property name="limitedTokens" value="VARIABLE_DEF"/&gt;
&lt;property name="maximumDepth" value="2"/&gt;
&lt;property name="maximumNumber" value="10"/&gt;
&lt;/module&gt;
</source>
<p>Too many returns from within a method:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="METHOD_DEF"/&gt;
&lt;property name="limitedTokens" value="LITERAL_RETURN"/&gt;
&lt;property name="maximumNumber" value="3"/&gt;
&lt;/module&gt;
</source>
<p>Too many fields within an interface:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="INTERFACE_DEF"/&gt;
&lt;property name="limitedTokens" value="VARIABLE_DEF"/&gt;
&lt;property name="maximumDepth" value="2"/&gt;
&lt;property name="maximumNumber" value="0"/&gt;
&lt;/module&gt;
</source>
<p>Limits the number of exceptions a method can throw:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="LITERAL_THROWS"/&gt;
&lt;property name="limitedTokens" value="IDENT"/&gt;
&lt;property name="maximumNumber" value="1"/&gt;
&lt;/module&gt;
</source>
<p>Limits the number of expressions in a method:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="METHOD_DEF"/&gt;
&lt;property name="limitedTokens" value="EXPR"/&gt;
&lt;property name="maximumNumber" value="200"/&gt;
&lt;/module&gt;
</source>
<p>Disallows empty statements:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="EMPTY_STAT"/&gt;
&lt;property name="limitedTokens" value="EMPTY_STAT"/&gt;
&lt;property name="maximumNumber" value="0"/&gt;
&lt;property name="maximumDepth" value="0"/&gt;
&lt;property name="maximumMessage"
value="Empty statement is not allowed."/&gt;
&lt;/module&gt;
</source>
<p>Too many fields within a class:</p>
<source>
&lt;module name="DescendantToken"&gt;
&lt;property name="tokens" value="CLASS_DEF"/&gt;
&lt;property name="limitedTokens" value="VARIABLE_DEF"/&gt;
&lt;property name="maximumDepth" value="2"/&gt;
&lt;property name="maximumNumber" value="10"/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="Indentation">
<subsection name="Description">
<p>
Checks correct indentation of Java code.
</p>
<p>
The idea behind this is that while pretty printers are
sometimes convenient for bulk reformats of legacy code, they often
either aren't configurable enough or just can't anticipate how
format should be done. Sometimes this is personal preference, other
times it is practical experience. In any case, this check should
just ensure that a minimal set of indentation rules is followed.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>basicOffset</td>
<td>how many spaces to use for new indentation level</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>4</td>
</tr>
<tr>
<td>braceAdjustment</td>
<td>how far braces should be indented when on the next line</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>0</td>
</tr>
<tr>
<td>caseIndent</td>
<td>how much to indent a case label</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>4</td>
</tr>
<tr>
<td>throwsIndent</td>
<td>how far a throws clause should be indented when on next line</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>4</td>
</tr>
<tr>
<td>arrayInitIndent</td>
<td>how much to indent an array initialisation when on next line</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>4</td>
</tr>
<tr>
<td>lineWrappingIndentation</td>
<td>how far continuation line should be indented when line-wrapping is present</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td>4</td>
</tr>
<tr>
<td>forceStrictCondition</td>
<td>force strict condition in line wrapping case. If value is true, line wrap indent
have to be same as lineWrappingIndentation parameter</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td>false</td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;Indentation&quot;/&gt;
</source>
<p>
To configure the check to enforce the indentation style recommended by
Oracle:
</p>
<source>
&lt;module name=&quot;Indentation&quot;&gt;
&lt;property name=&quot;caseIndent&quot; value=&quot;0&quot;/&gt;
&lt;/module&gt;
</source>
<p>
To configure the Check to enforce strict condition in line-wrapping validation.
</p>
<source>
&lt;module name=&quot;Indentation&quot;&gt;
&lt;property name=&quot;forceStrictCondition&quot; value=&quot;true&quot;/&gt;
&lt;/module&gt;
</source>
<p>
Such config doesn't allow next cases:
</p>
<source>
void foo(String aFooString,
int aFooInt) {} // indent:8 ; expected: 4; warn, because 8 != 4
</source>
<p>
But if forceStrictCondition = false, this code is valid:
</p>
<source>
void foo(String aFooString,
int aFooInt) {} // indent:8 ; expected: > 4; ok, because 8 > 4
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks.indentation
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="TrailingComment">
<subsection name="Description">
<p>
The check to ensure that requires that comments be the only thing on
a line. For the case of <code>//</code> comments that means that the only thing
that should precede it is whitespace. It doesn't check comments if
they do not end a line; for example, it accepts the following:
<code>Thread.sleep( 10 &lt;some comment here&gt; );</code> Format
property is intended to deal with the "} // while" example.
</p>
<p>
Rationale: Steve McConnel in <cite>Code Complete</cite> suggests that
endline comments are a bad practice. An end line comment would be
one that is on the same line as actual code. For example:
</p>
<source>
a = b + c; // Some insightful comment
d = e / f; // Another comment for this line
</source>
<p>
Quoting <cite>Code Complete</cite> for the justification:
</p>
<ul>
<li> &quot;The comments have to be aligned so that they do not
interfere with the visual structure of the code. If you don't align
them neatly, they'll make your listing look like it's been through a
washing machine.&quot;
</li>
<li> &quot;Endline comments tend to be hard to format...It takes
time to align them. Such time is not spent learning more about the
code; it's dedicated solely to the tedious task of pressing the
spacebar or tab key.&quot;
</li>
<li> &quot;Endline comments are also hard to maintain. If the code
on any line containing an endline comment grows, it bumps the
comment farther out, and all the other endline comments will have to
bumped out to match. Styles that are hard to maintain aren't
maintained....&quot;
</li>
<li> &quot;Endline comments also tend to be cryptic. The right side
of the line doesn't offer much room and the desire to keep the
comment on one line means the comment must be short. Work then goes
into making the line as short as possible instead of as clear as
possible. The comment usually ends up as cryptic as
possible....&quot;
</li>
<li> &quot;A systemic problem with endline comments is that it's
hard to write a meaningful comment for one line of code. Most
endline comments just repeat the line of code, which hurts more than
it helps.&quot;
</li>
</ul>
<p>
McConnel's comments on being hard to maintain when the size of the line
changes are even more important in the age of automated
refactorings.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>format</td>
<td>pattern for strings allowed before the comment</td>
<td><a href="property_types.html#regexp">regular expression</a></td>
<td><code>^[\\s\\}\\);]*$</code></td>
</tr>
<tr>
<td>legalComment</td>
<td>pattern for text allowed in trailing comments. (This
pattern will not be applied to multiline comments and the text of the
comment will be trimmed before matching.)</td>
<td><a href="property_types.html#regexp">regular expression</a></td>
<td>(not set)</td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;TrailingComment&quot;/&gt;
</source>
<p>
To configure the check so it enforces only comment on a line:
</p>
<source>
&lt;module name=&quot;TrailingComment&quot;&gt;
&lt;property name=&quot;format&quot; value=&quot;^\\s*$&quot;/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks.indentation
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="Regexp">
<subsection name="Description">
<p>
A check that makes sure that a specified pattern exists, exists less
than a set number of times, or does not exist in the file.
</p>
<p>
This check combines all the functionality provided by
<a href="config_header.html#RegexpHeader">RegexpHeader</a>
except supplying the regular expression from a file.
</p>
<p>
It differs from them in that it works in multiline mode.
Its regular expression can span multiple lines and it checks this
against the whole file at once.
The others work in singleline mode.
Their single or multiple regular expressions can only span one line.
They check each of these against each line in the file in turn.
</p>
<p>
<b>Note:</b> Because of the different mode of operation there may be
some changes in the regular expressions used to achieve a particular end.
</p>
<p>In multiline mode...</p>
<ul>
<li> <code>^</code> means the beginning of a line, as opposed to beginning of the input.</li>
<li> For beginning of the input use <code>\A</code>.</li>
<li> <code>$</code> means the end of a line, as opposed to the end of the input.</li>
<li> For end of input use <code>\Z</code>.</li>
<li> Each line in the file is terminated with a line feed character.</li>
</ul>
<p>
<b>Note:</b> Not all regular expression engines are created equal. Some provide extra
functions that others do not and some elements of the syntax may vary.
This check makes use of the <a
href="https://docs.oracle.com/javase/7/docs/api/java/util/regex/package-summary.html">
java.util.regex package</a>; please check its documentation for
details of how to construct a regular expression to achieve a particular
goal.
</p>
<p>
<b>Note:</b> When entering a regular expression as a parameter in the
XML config file you must also take into account the XML rules. e.g. if
you want to match a &lt; symbol you need to enter &amp;lt;. The regular
expression should be entered on one line.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>format</td>
<td>pattern</td>
<td><a href="property_types.html#regexp">regular expression</a></td>
<td><code>$^</code> (empty)</td>
</tr>
<tr>
<td>message</td>
<td>message which is used to notify about violations,
if empty then the default (hard-coded) message is used.</td>
<td><a href="property_types.html#string">String</a></td>
<td><code>&quot;&quot;</code>(empty)</td>
</tr>
<tr>
<td>illegalPattern</td>
<td>Controls whether the pattern is required or illegal.</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td><code>false</code></td>
</tr>
<tr>
<td>duplicateLimit</td>
<td>Controls whether to check for duplicates of a required pattern,
any negative value means no checking for duplicates, any positive
value is used as the maximum number of allowed duplicates, if the
limit is exceeded errors will be logged.</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td><code>-1</code></td>
</tr>
<tr>
<td>errorLimit</td>
<td>Controls the maximum number of errors before the check will abort.</td>
<td><a href="property_types.html#integer">Integer</a></td>
<td><code>100</code></td>
</tr>
<tr>
<td>ignoreComments</td>
<td>Controls whether to ignore matches found within comments.</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td><code>false</code></td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
The following examples are mainly copied from the other 3 checks
mentioned above, to show how the same results can be achieved using
this check in place of them.
</p>
<p>
<b>To use like Required Regexp check:</b>
</p>
<p>
An example of how to configure the check to make sure a copyright
statement is included in the file:
</p>
<p> The statement. </p>
<source>
// This code is copyrighted
</source>
<p> The check. </p>
<source>
&lt;module name="Regexp"&gt;
&lt;property name="format" value="// This code is copyrighted"/&gt;
&lt;/module&gt;
</source>
<p> Your statement may be multiline. </p>
<source>
// This code is copyrighted
// (c) MyCompany
</source>
<p> Then the check would be. </p>
<source>
&lt;module name="Regexp"&gt;
&lt;property name="format" value="// This code is copyrighted\n// \(c\) MyCompany"/&gt;
&lt;/module&gt;
</source>
<p><b>Note:</b> To search for parentheses () in a regular expression
you must escape them like \(\). This is required by the regexp engine,
otherwise it will think they are special instruction characters.
</p>
<p>
And to make sure it appears only once:
</p>
<source>
&lt;module name="Regexp"&gt;
&lt;property name="format" value="// This code is copyrighted\n// \(c\) MyCompany"/&gt;
&lt;property name=&quot;duplicateLimit&quot; value=&quot;0&quot;/&gt;
&lt;/module&gt;
</source>
<p>
It can also be useful to attach a meaningful message to the check:
</p>
<source>
&lt;module name="Regexp"&gt;
&lt;property name="format" value="// This code is copyrighted\n// \(c\) MyCompany"/&gt;
&lt;property name=&quot;message&quot; value=&quot;Copyright&quot;/&gt;
&lt;/module&gt;
</source>
<p>
<b>To use like illegal regexp check:</b>
</p>
<p>
An example of how to configure the check to make sure there are no
calls to <code>System.out.println</code>:
</p>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;!-- . matches any character, so we need to escape it and use \. to match dots. --&gt;
&lt;property name="format" value="System\.out\.println"/&gt;
&lt;property name="illegalPattern" value="true"/&gt;
&lt;/module&gt;
</source>
<p>
You may want to make the above check ignore comments, like this:
</p>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;property name="format" value="System\.out\.println"/&gt;
&lt;property name="illegalPattern" value="true"/&gt;
&lt;property name="ignoreComments" value="true"/&gt;
&lt;/module&gt;
</source>
<p>
An example of how to configure the check to find trailing whitespace
at the end of a line:
</p>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;property name="format" value="[ \t]+$"/&gt;
&lt;property name="illegalPattern" value="true"/&gt;
&lt;property name=&quot;message&quot; value=&quot;Trailing whitespace&quot;/&gt;
&lt;/module&gt;
</source>
<p>
An example of how to configure the check to find case-insensitive
occurrences of &quot;debug&quot;:
</p>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;property name="format" value="(?i)debug"/&gt;
&lt;property name="illegalPattern" value="true"/&gt;
&lt;/module&gt;
</source>
<p>
<b>Note:</b> The (?i) at the beginning of the regular expression
tells the regexp engine to ignore the case.
</p>
<p>
There is also a feature to limit the number of errors reported.
When the limit is reached the check aborts with a message
reporting that the limit has been reached.
The default limit setting is 100, but this can be change as shown in
the following example.
</p>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;property name="format" value="(?i)debug"/&gt;
&lt;property name="illegalPattern" value="true"/&gt;
&lt;property name="errorLimit" value="1000"/&gt;
&lt;/module&gt;
</source>
<p>
<b>To use like <a
href="config_header.html#RegexpHeader">RegexpHeader
</a>:</b>
</p>
<p>
To configure the check to verify that each file starts with the
following multiline header.
</p>
<p>Note the following:</p>
<ul>
<li>\A means the start of the file.</li>
<li>The date can be any 4 digit number.</li>
</ul>
<source>
// Copyright (C) 2004 MyCompany
// All rights reserved
</source>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;property
name=&quot;format&quot;
value=&quot;\A// Copyright \(C\) \d\d\d\d MyCompany\n// All rights reserved&quot;/&gt;
&lt;/module&gt;
</source>
<p>
A more complex example. Note how the import and javadoc multilines are
handled, there can be any number of them.
</p>
<source>
///////////////////////////////////////////////////////////////////////
// checkstyle:
// Checks Java source code for adherence to a set of rules.
// Copyright (C) 2004 Oliver Burn
// Last modification by $Author A.N.Other$
///////////////////////////////////////////////////////////////////////
package com.puppycrawl.checkstyle;
import java.util.thing1;
import java.util.thing2;
import java.util.thing3;
/**
* javadoc line 1
* javadoc line 2
* javadoc line 3
*/
</source>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;property
name=&quot;format&quot;
value=&quot;\A/{71}\n// checkstyle:\n// Checks Java source code for
adherence to a set of rules\.\n// Copyright \(C\) \d\d\d\d Oliver Burn\n
// Last modification by \$Author.*\$\n/{71}\n\npackage [\w\.]*;\n\n
(import [\w\.]*;\n)*\n/\*\*\n( \*[^/]*\n)* \*/&quot;/&gt;
&lt;/module&gt;
</source>
<p>
<b>More examples:</b>
</p>
<p>
The next 2 examples deal with the following example Java source file:
</p>
<source>
/*
* PID.java
*
* Copyright (c) 2001 ACME
* 123 Some St.
* Somewhere.
*
* This software is the confidential and proprietary information of ACME.
* ("Confidential Information"). You shall not disclose such
* Confidential Information and shall use it only in accordance with
* the terms of the license agreement you entered into with ACME.
*
* $Log: config_misc.xml,v $
* Revision 1.7 2007/01/16 12:16:35 oburn
* Removing all reference to mailing lists
*
* Revision 1.6 2005/12/25 16:13:10 o_sukhodolsky
* Fix for rfe 1248106 (TYPECAST is now accepted by NoWhitespaceAfter)
*
* Fix for rfe 953266 (thanks to Paul Guyot (pguyot) for submitting patch)
* IllegalType can be configured to accept some abstract classes which
* matches to regexp of illegal type names (property legalAbstractClassNames)
*
* TrailingComment now can be configured to accept some trailing comments
* (such as NOI18N) (property legalComment, rfe 1385344).
*
* Revision 1.5 2005/11/06 11:54:12 oburn
* Incorporate excellent patch [ 1344344 ] Consolidation of regexp checks.
*
* Revision 1.3.8.1 2005/10/11 14:26:32 someone
* Fix for bug 251. The broken bit is fixed
*/
package com.acme.tools;
import com.acme.thing1;
import com.acme.thing2;
import com.acme.thing3;
/**
*
* &lt;P&gt;
* &lt;I&gt;This software is the confidential and proprietary information of
* ACME (&lt;B&gt;"Confidential Information"&lt;/B&gt;). You shall not
* disclose such Confidential Information and shall use it only in
* accordance with the terms of the license agreement you entered into
* with ACME.&lt;/I&gt;
* &lt;/P&gt;
*
* &amp;#169; copyright 2002 ACME
*
* @author Some Body
*/
public class PID extends StateMachine implements WebObject.Constants {
/** javadoc. */
public static final int A_SETPOINT = 1;
.
.
.
} // class PID
</source>
<p>
This checks for the presence of the header, the first 16 lines.
</p>
<p>Note the following:</p>
<ul>
<li>Line 2 and 13 contain the file name. These are checked to
make sure they are the same, and that they match the class name.</li>
<li>The date can be any 4 digit number.</li>
</ul>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;property
name=&quot;format&quot;
value=&quot;\A/\*\n \* (\w*)\.java\n \*\n \* Copyright \(c\)
\d\d\d\d ACME\n \* 123 Some St\.\n \* Somewhere\.\n \*\n
\* This software is the confidential and proprietary information
of ACME\.\n \* \(&quot;Confidential Information&quot;\)\. You
shall not disclose such\n \* Confidential Information and shall
use it only in accordance with\n \* the terms of the license
agreement you entered into with ACME\.\n \*\n
\* \$Log: config_misc.xml,v $
\* \Revision 1.7 2007/01/16 12:16:35 oburn
\* \Removing all reference to mailing lists
\* \
\* \Revision 1.6 2005/12/25 16:13:10 o_sukhodolsky
\* \Fix for rfe 1248106 (TYPECAST is now accepted by NoWhitespaceAfter)
\* \
\* \Fix for rfe 953266 (thanks to Paul Guyot (pguyot) for submitting patch)
\* \IllegalType can be configured to accept some abstract classes which
\* \matches to regexp of illegal type names (property legalAbstractClassNames)
\* \
\* \TrailingComment now can be configured to accept some trailing comments
\* \(such as NOI18N) (property legalComment, rfe 1385344).
\* \
\* \Revision 1.5 2005/11/06 11:54:12 oburn
\* \Incorporate excellent patch [ 1344344 ] Consolidation of regexp checks.
\* \\n(.*\n)*([\w|\s]*( class | interface )\1)&quot;/&gt;
&lt;property name=&quot;message&quot; value=&quot;Correct header not found&quot;/&gt;
&lt;/module&gt;
</source>
<p>
This checks for the presence of a copyright notice within the class
javadoc, lines 24 to 37.
</p>
<source>
&lt;module name=&quot;Regexp&quot;&gt;
&lt;property
name=&quot;format&quot;
value=&quot;(/\*\*\n)( \*.*\n)*( \* &amp;lt;P&amp;gt;\n \* &amp;lt;I&amp;gt;
This software is the confidential and proprietary information of\n
\* ACME \(&amp;lt;B&amp;gt;&amp;quot;Confidential Information&amp;quot;&amp;lt;/B&amp;gt;
\)\. You shall not\n \* disclose such Confidential Information
and shall use it only in\n \* accordance with the terms of the
license agreement you entered into\n \* with ACME\.&amp;lt;/I&amp;gt;\n
\* &amp;lt;/P&amp;gt;\n \*\n \* &amp;#169; copyright \d\d\d\d ACME\n
\*\n \* @author .*)(\n\s\*.*)*/\n[\w|\s]*( class | interface )&quot;/&gt;
&lt;property name=&quot;message&quot; value=&quot;Copyright in class/interface Javadoc&quot;/&gt;
&lt;property name=&quot;duplicateLimit&quot; value=&quot;0&quot;/&gt;
&lt;/module&gt;
</source>
<p>
<b>Note:</b> To search for things that mean something in XML, like
&lt; you need to escape them like &amp;lt;. This is required so the
XML parser does not act on them, but instead passes the correct
character to the regexp engine.
</p>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="OuterTypeFilename">
<subsection name="Description">
<p>
Checks that the outer type name and the file name match. For example,
the class <code>Foo</code> must be in a file named
<code>Foo.java</code>.
</p>
</subsection>
<subsection name="Properties">
<p>None.</p>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;OuterTypeFilename&quot;/&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="UniqueProperties">
<subsection name="Description">
<p>
Checks properties files for duplicated properties.
</p>
<p>
Rationale: Multiple property keys usually appear after merge
or rebase of several branches. While there are no errors in
runtime, there can be a confusion due to having different values
for the duplicated properties.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>fileExtensions</td>
<td>file type extension of the files to check.</td>
<td><a href="property_types.html#stringSet">String Set</a></td>
<td>properties</td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;UniqueProperties&quot;&gt;
&lt;property name=&quot;fileExtensions&quot; value=&quot;properties&quot; /&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#Checker">Checker</a>
</p>
</subsection>
</section>
<section name="AvoidEscapedUnicodeCharacters">
<subsection name="Description">
<p>
Restrict using <a href = "http://docs.oracle.com/javase/specs/jls/se7/html/jls-3.html#jls-3.3">
Unicode escapes</a> (e.g. \u221e).
It is possible to allow using escapes for
<a href="http://en.wiktionary.org/wiki/Appendix:Control_characters"> non-printable(control) characters</a>.
Also, this check can be configured to allow using escapes
if trail comment is present. By the option it is possible to
allow using escapes if literal contains only them.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>allowEscapesForControlCharacters</td>
<td>Allow use escapes for non-printable(control) characters.</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td>false</td>
</tr>
<tr>
<td>allowByTailComment</td>
<td>Allow use escapes if trail comment is present.</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td>false</td>
</tr>
<tr>
<td>allowIfAllCharactersEscaped</td>
<td>Allow if all characters in literal are escaped.</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td>false</td>
</tr>
<tr>
<td>allowNonPrintableEscapes</td>
<td>Allow non-printable escapes.</td>
<td><a href="property_types.html#boolean">Boolean</a></td>
<td>false</td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
Examples of using Unicode:
</p>
<source>
String unitAbbrev = "μs"; //Best: perfectly clear even without a comment.
String unitAbbrev = "\u03bcs"; //Poor: the reader has no idea what this is.
</source>
<p>
An example of how to configure the check is:
</p>
<source>
&lt;module name=&quot;AvoidEscapedUnicodeCharacters&quot;/&gt;
</source>
<p>
An example of non-printable(control) characters.
</p>
<source>
return '\ufeff' + content; // byte order mark
</source>
<p>
An example of how to configure the check to allow using escapes
for non-printable(control) characters:
</p>
<source>
&lt;module name="AvoidEscapedUnicodeCharacters"&gt;
&lt;property name="allowEscapesForControlCharacters" value="true"/&gt;
&lt;/module&gt;
</source>
<p>
Example of using escapes with trail comment:
</p>
<source>
String unitAbbrev = "\u03bcs"; // Greek letter mu, "s"
</source>
<p>
An example of how to configure the check to allow using escapes
if trail comment is present:
</p>
<source>
&lt;module name="AvoidEscapedUnicodeCharacters"&gt;
&lt;property name="allowByTailComment" value="true"/&gt;
&lt;/module&gt;
</source>
<p>
Example of using escapes if literal contains only them:
</p>
<source>
String unitAbbrev = "\u03bc\u03bc\u03bc";
</source>
<p>
An example of how to configure the check to allow escapes
if literal contains only them:
</p>
<source>
&lt;module name="AvoidEscapedUnicodeCharacters"&gt;
&lt;property name="allowIfAllCharactersEscaped" value="true"/&gt;
&lt;/module&gt;
</source>
<p>
An example of how to configure the check to allow non-printable escapes:
</p>
<source>
&lt;module name="AvoidEscapedUnicodeCharacters"&gt;
&lt;property name="allowNonPrintableEscapes" value="true"/&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#TreeWalker">TreeWalker</a>
</p>
</subsection>
</section>
<section name="UniqueProperties">
<subsection name="Description">
<p>
Checks properties file for a duplicated properties.
</p>
<p>
Rationale: Multiple property keys usually appears after merge
or rebase of several branches. While there is no errors in
runtime, there can be a confusion on having different values
for the duplicated properties.
</p>
</subsection>
<subsection name="Properties">
<table>
<tr>
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>fileExtensions</td>
<td>file type extension of the files to check.</td>
<td><a href="property_types.html#stringSet">String Set</a></td>
<td>properties</td>
</tr>
</table>
</subsection>
<subsection name="Examples">
<p>
To configure the check:
</p>
<source>
&lt;module name=&quot;UniqueProperties&quot;&gt;
&lt;property name=&quot;fileExtensions&quot; value=&quot;properties&quot; /&gt;
&lt;/module&gt;
</source>
</subsection>
<subsection name="Package">
<p>
com.puppycrawl.tools.checkstyle.checks
</p>
</subsection>
<subsection name="Parent Module">
<p>
<a href="config.html#Checker">Checker</a>
</p>
</subsection>
</section>
</body>
</document>