tools/maven/checkstyle.xml - flink-connector-prometheus - Git at Google

 <?xml version="1.0"?>
 <!--
 Licensed to the Apache Software Foundation (ASF) under one
 or more contributor license agreements.  See the NOTICE file
 distributed with this work for additional information
 regarding copyright ownership.  The ASF licenses this file
 to you under the Apache License, Version 2.0 (the
 "License"); you may not use this file except in compliance
 with the License.  You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing,
 software distributed under the License is distributed on an
 "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 KIND, either express or implied.  See the License for the
 specific language governing permissions and limitations
 under the License.
 -->
 <!DOCTYPE module PUBLIC
 		"-//Puppy Crawl//DTD Check Configuration 1.3//EN"
 		"http://www.puppycrawl.com/dtds/configuration_1_3.dtd">

 <!--
 This is a checkstyle configuration file. For descriptions of
 what the following rules do, please see the checkstyle configuration
 page at http://checkstyle.sourceforge.net/config.html.

 This file is based on the checkstyle file of Apache Beam.
 -->

 <module name="Checker">

 	<module name="RegexpSingleline">
 		<!-- Checks that TODOs don't have stuff in parenthesis, e.g., username. -->
 		<property name="format" value="((//.*)|(\*.*))TODO\("/>
 		<property name="message" value="TODO comments must not include usernames."/>
 		<property name="severity" value="error"/>
 	</module>

 	<module name="RegexpSingleline">
 		<property name="format" value="\s+$"/>
 		<property name="message" value="Trailing whitespace"/>
 		<property name="severity" value="error"/>
 	</module>

 	<module name="RegexpSingleline">
 		<property name="format" value="Throwables.propagate\("/>
 		<property name="message" value="Throwables.propagate is deprecated"/>
 		<property name="severity" value="error"/>
 	</module>

 	<module name="SuppressionFilter">
 		<property name="file" value="${checkstyle.suppressions.file}" default="suppressions.xml"/>
 	</module>

 	<!--

 	FLINK CUSTOM CHECKS

 	-->

 	<module name="FileLength">
 		<property name="max" value="3100"/>
 	</module>

 	<!-- All Java AST specific tests live under TreeWalker module. -->
 	<module name="TreeWalker">

 		<!-- Allow use of comment to suppress javadocstyle -->
 		<module name="SuppressionCommentFilter">
 			<property name="offCommentFormat" value="CHECKSTYLE.OFF\: ([\w\|]+)"/>
 			<property name="onCommentFormat" value="CHECKSTYLE.ON\: ([\w\|]+)"/>
 			<property name="checkFormat" value="$1"/>
 		</module>

 		<!--

 		FLINK CUSTOM CHECKS

 		-->

 		<!-- Prohibit T.getT() methods for standard boxed types -->
 		<module name="Regexp">
 			<property name="format" value="Boolean\.getBoolean"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message" value="Use System.getProperties() to get system properties."/>
 		</module>

 		<module name="Regexp">
 			<property name="format" value="Integer\.getInteger"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message" value="Use System.getProperties() to get system properties."/>
 		</module>

 		<module name="Regexp">
 			<property name="format" value="Long\.getLong"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message" value="Use System.getProperties() to get system properties."/>
 		</module>

 		<!--

 		IllegalImport cannot blacklist classes so we have to fall back to Regexp.

 		-->

 		<!-- forbid use of commons lang validate -->
 		<module name="Regexp">
 			<property name="format" value="org\.apache\.commons\.lang3\.Validate"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message"
 					  value="Use Guava Checks instead of Commons Validate. Please refer to the coding guidelines."/>
 		</module>
 		<!-- forbid the use of google.common.base.Preconditions -->
 		<module name="Regexp">
 			<property name="format" value="import com\.google\.common\.base\.Preconditions"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message"
 					  value="Use Flink's Preconditions instead of Guava's Preconditions"/>
 		</module>
 		<!-- forbid the use of com.google.common.annotations.VisibleForTesting -->
 		<module name="Regexp">
 			<property name="format"
 					  value="import com\.google\.common\.annotations\.VisibleForTesting"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message"
 					  value="Use Flink's VisibleForTesting instead of Guava's VisibleForTesting"/>
 		</module>
 		<module name="Regexp">
 			<property name="format" value="import static com\.google\.common\.base\.Preconditions"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message"
 					  value="Use Flink's Preconditions instead of Guava's Preconditions"/>
 		</module>
 		<!-- forbid the use of org.apache.commons.lang.SerializationUtils -->
 		<module name="Regexp">
 			<property name="format" value="org\.apache\.commons\.lang\.SerializationUtils"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message"
 					  value="Use Flink's InstantiationUtil instead of common's SerializationUtils"/>
 		</module>
 		<module name="Regexp">
 			<property name="format" value="org\.apache\.commons\.lang3\.SerializationUtils"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message"
 					  value="Use Flink's InstantiationUtil instead of common's SerializationUtils"/>
 		</module>
 		<module name="Regexp">
 			<property name="format" value="org\.apache\.commons\.lang\."/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message" value="Use commons-lang3 instead of commons-lang."/>
 		</module>
 		<module name="Regexp">
 			<property name="format" value="org\.codehaus\.jettison"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message" value="Use com.fasterxml.jackson instead of jettison."/>
 		</module>
 		<module name="Regexp">
 			<property name="format" value="org\.testcontainers\.shaded"/>
 			<property name="illegalPattern" value="true"/>
 			<property name="message" value="Use utilities from appropriate library instead of org.testcontainers."/>
 		</module>

 		<!-- Enforce Java-style array declarations -->
 		<module name="ArrayTypeStyle"/>

 		<module name="TodoComment">
 			<!-- Checks that disallowed strings are not used in comments.  -->
 			<property name="format" value="(FIXME)|(XXX)|(@author)"/>
 		</module>

 		<!--

 		IMPORT CHECKS

 		-->

 		<module name="AvoidStarImport">
 			<property name="severity" value="error"/>
 		</module>

 		<module name="IllegalImport">
 			<property name="illegalPkgs"
 					  value="org.mockito, org.powermock"/>
 			<message key="import.illegal" value="{0}; Mocking is discouraged. Please refer to the coding guidelines: https://flink.apache.org/how-to-contribute/code-style-and-quality-common/#avoid-mockito---use-reusable-test-implementations."/>
 		</module>
 		<module name="IllegalImport">
 			<property name="illegalPkgs"
 					  value="autovalue.shaded, avro.shaded, com.google.api.client.repackaged, com.google.appengine.repackaged"/>
 		</module>
 		<module name="IllegalImport">
 			<property name="illegalPkgs" value="org.codehaus.jackson"/>
 			<message key="import.illegal" value="{0}; Use flink-shaded-jackson instead."/>
 		</module>
 		<module name="IllegalImport">
 			<property name="illegalPkgs" value="com.jayway.jsonpath"/>
 			<message key="import.illegal" value="{0}; Use flink-shaded-jsonpath instead."/>
 		</module>
 		<module name="IllegalImport">
 			<property name="illegalPkgs" value="org.objectweb.asm"/>
 			<message key="import.illegal" value="{0}; Use flink-shaded-asm instead."/>
 		</module>
 		<module name="IllegalImport">
 			<property name="illegalPkgs" value="io.netty"/>
 			<message key="import.illegal" value="{0}; Use flink-shaded-netty instead."/>
 		</module>
 		<module name="IllegalImport">
 			<property name="illegalPkgs" value="com.google.common"/>
 			<message key="import.illegal" value="{0}; Use flink-shaded-guava instead."/>
 		</module>

 		<module name="RedundantModifier">
 			<!-- Checks for redundant modifiers on various symbol definitions.
 			  See: https://checkstyle.sourceforge.io/checks/modifier/redundantmodifier.html#RedundantModifier

 			  We exclude METHOD_DEF to allow final methods in final classes to make them more future-proof.
 			-->
 			<property name="tokens"
 					  value="VARIABLE_DEF, ANNOTATION_FIELD_DEF, INTERFACE_DEF, CLASS_DEF, ENUM_DEF"/>
 		</module>

 		<!--
 			IllegalImport cannot blacklist classes, and c.g.api.client.util is used for some shaded
 			code and some useful code. So we need to fall back to Regexp.
 		-->

 		<!--
 			 Require static importing from Preconditions.
 		-->
 		<module name="RegexpSinglelineJava">
 			<property name="format" value="^import com.google.common.base.Preconditions;$"/>
 			<property name="message" value="Static import functions from Guava Preconditions"/>
 		</module>

 		<!--
 			The Nullable & Nonnull annotations check.
 		-->
 		<module name="RegexpSinglelineJava">
 			<property name="format" value="^import org.jetbrains.annotations.Nullable;$"/>
 			<property name="message" value="Use import javax.annotation.Nullable"/>
 		</module>

 		<module name="RegexpSinglelineJava">
 			<property name="format" value="^import org.jetbrains.annotations.NotNull;$"/>
 			<property name="message" value="Use import javax.annotation.Nonnull"/>
 		</module>

 		<!--

 		JAVADOC CHECKS

 		-->

 		<!-- Checks for Javadoc comments.                     -->
 		<!-- See https://checkstyle.sourceforge.io/checks/javadoc/javadocmethod.html -->
 		<module name="JavadocMethod">
 			<property name="accessModifiers" value="protected"/>
 			<property name="severity" value="error"/>
 			<property name="allowMissingParamTags" value="true"/>
 			<property name="allowMissingReturnTag" value="true"/>
 		</module>

 		<!-- Check that paragraph tags are used correctly in Javadoc. -->
 		<module name="JavadocParagraph"/>

 		<module name="JavadocType">
 			<property name="scope" value="protected"/>
 			<property name="severity" value="error"/>
 			<property name="allowMissingParamTags" value="true"/>
 		</module>

 		<module name="JavadocStyle">
 			<property name="severity" value="error"/>
 			<property name="checkHtml" value="true"/>
 		</module>

 		<!--

 		NAMING CHECKS

 		-->

 		<!-- Item 38 - Adhere to generally accepted naming conventions -->

 		<module name="PackageName">
 			<!-- Validates identifiers for package names against the
 			  supplied expression. -->
 			<!-- Here the default checkstyle rule restricts package name parts to
 			  seven characters, this is not in line with common practice at Google.
 			-->
 			<property name="format" value="^[a-z]+(\.[a-z][a-z0-9]{1,})*$"/>
 			<property name="severity" value="error"/>
 		</module>

 		<module name="TypeNameCheck">
 			<!-- Validates static, final fields against the
 			expression "^[A-Z][a-zA-Z0-9]*$". -->
 			<metadata name="altname" value="TypeName"/>
 			<property name="severity" value="error"/>
 		</module>

 		<module name="ConstantNameCheck">
 			<!-- Validates non-private, static, final fields against the supplied
 			public/package final fields "^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$". -->
 			<metadata name="altname" value="ConstantName"/>
 			<property name="applyToPublic" value="true"/>
 			<property name="applyToProtected" value="true"/>
 			<property name="applyToPackage" value="true"/>
 			<property name="applyToPrivate" value="false"/>
 			<property name="format" value="^([A-Z][A-Z0-9]*(_[A-Z0-9]+)*|FLAG_.*)$"/>
 			<message key="name.invalidPattern"
 					 value="Variable ''{0}'' should be in ALL_CAPS (if it is a constant) or be private (otherwise)."/>
 			<property name="severity" value="error"/>
 		</module>

 		<module name="StaticVariableNameCheck">
 			<!-- Validates static, non-final fields against the supplied
 			expression "^[a-z][a-zA-Z0-9]*_?$". -->
 			<metadata name="altname" value="StaticVariableName"/>
 			<property name="applyToPublic" value="true"/>
 			<property name="applyToProtected" value="true"/>
 			<property name="applyToPackage" value="true"/>
 			<property name="applyToPrivate" value="true"/>
 			<property name="format" value="^[a-z][a-zA-Z0-9]*_?$"/>
 			<property name="severity" value="error"/>
 		</module>

 		<module name="MemberNameCheck">
 			<!-- Validates non-static members against the supplied expression. -->
 			<metadata name="altname" value="MemberName"/>
 			<property name="applyToPublic" value="true"/>
 			<property name="applyToProtected" value="true"/>
 			<property name="applyToPackage" value="true"/>
 			<property name="applyToPrivate" value="true"/>
 			<property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
 			<property name="severity" value="error"/>
 		</module>

 		<module name="MethodNameCheck">
 			<!-- Validates identifiers for method names. -->
 			<metadata name="altname" value="MethodName"/>
 			<property name="format" value="^[a-z][a-zA-Z0-9]*(_[a-zA-Z0-9]+)*$"/>
 			<property name="severity" value="error"/>
 		</module>

 		<module name="ParameterName">
 			<!-- Validates identifiers for method parameters against the
 			  expression "^[a-z][a-zA-Z0-9]*$". -->
 			<property name="severity" value="error"/>
 		</module>

 		<module name="LocalFinalVariableName">
 			<!-- Validates identifiers for local final variables against the
 			  expression "^[a-z][a-zA-Z0-9]*$". -->
 			<property name="severity" value="error"/>
 		</module>

 		<module name="LocalVariableName">
 			<!-- Validates identifiers for local variables against the
 			  expression "^[a-z][a-zA-Z0-9]*$". -->
 			<property name="severity" value="error"/>
 		</module>

 		<!--

 		LENGTH and CODING CHECKS

 		-->

 		<!-- Checks for braces around if and else blocks -->
 		<module name="NeedBraces">
 			<property name="severity" value="error"/>
 			<property name="tokens"
 					  value="LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO"/>
 		</module>

 		<module name="UpperEll">
 			<!-- Checks that long constants are defined with an upper ell.-->
 			<property name="severity" value="error"/>
 		</module>

 		<module name="FallThrough">
 			<!-- Warn about falling through to the next case statement.  Similar to
 			javac -Xlint:fallthrough, but the check is suppressed if a single-line comment
 			on the last non-blank line preceding the fallen-into case contains 'fall through' (or
 			some other variants that we don't publicized to promote consistency).
 			-->
 			<property name="reliefPattern"
 					  value="fall through|Fall through|fallthru|Fallthru|falls through|Falls through|fallthrough|Fallthrough|No break|NO break|no break|continue on"/>
 			<property name="severity" value="error"/>
 		</module>

 		<!-- Checks for over-complicated boolean expressions. -->
 		<module name="SimplifyBooleanExpression"/>

 		<!-- Detects empty statements (standalone ";" semicolon). -->
 		<module name="EmptyStatement"/>

 		<!-- Detect multiple consecutive semicolons (e.g. ";;"). -->
 		<module name="RegexpSinglelineJava">
 			<property name="format" value=";{2,}"/>
 			<property name="message" value="Use one semicolon"/>
 			<property name="ignoreComments" value="true"/>
 		</module>


 		<!--

 		WHITESPACE CHECKS

 		-->

 		<module name="EmptyLineSeparator">
 			<!-- Checks for empty line separator between tokens. The only
 				 excluded token is VARIABLE_DEF, allowing class fields to
 				 be declared on consecutive lines.
 			-->
 			<property name="allowMultipleEmptyLines" value="false"/>
 			<property name="allowMultipleEmptyLinesInsideClassMembers" value="false"/>
 			<property name="tokens" value="PACKAGE_DEF, IMPORT, STATIC_IMPORT, CLASS_DEF,
         INTERFACE_DEF, ENUM_DEF, STATIC_INIT, INSTANCE_INIT, METHOD_DEF,
         CTOR_DEF"/>
 		</module>
 	</module>
 </module>
	<?xml version="1.0"?>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one
	or more contributor license agreements. See the NOTICE file
	distributed with this work for additional information
	regarding copyright ownership. The ASF licenses this file
	to you under the Apache License, Version 2.0 (the
	"License"); you may not use this file except in compliance
	with the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing,
	software distributed under the License is distributed on an
	"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	KIND, either express or implied. See the License for the
	specific language governing permissions and limitations
	under the License.
	-->
	<!DOCTYPE module PUBLIC
	"-//Puppy Crawl//DTD Check Configuration 1.3//EN"
	"http://www.puppycrawl.com/dtds/configuration_1_3.dtd">

	<!--
	This is a checkstyle configuration file. For descriptions of
	what the following rules do, please see the checkstyle configuration
	page at http://checkstyle.sourceforge.net/config.html.

	This file is based on the checkstyle file of Apache Beam.
	-->

	<module name="Checker">

	<module name="RegexpSingleline">
	<!-- Checks that TODOs don't have stuff in parenthesis, e.g., username. -->
	<property name="format" value="((//.)\|(\.*))TODO\("/>
	<property name="message" value="TODO comments must not include usernames."/>
	<property name="severity" value="error"/>
	</module>

	<module name="RegexpSingleline">
	<property name="format" value="\s+$"/>
	<property name="message" value="Trailing whitespace"/>
	<property name="severity" value="error"/>
	</module>

	<module name="RegexpSingleline">
	<property name="format" value="Throwables.propagate\("/>
	<property name="message" value="Throwables.propagate is deprecated"/>
	<property name="severity" value="error"/>
	</module>

	<module name="SuppressionFilter">
	<property name="file" value="${checkstyle.suppressions.file}" default="suppressions.xml"/>
	</module>

	<!--

	FLINK CUSTOM CHECKS

	-->

	<module name="FileLength">
	<property name="max" value="3100"/>
	</module>

	<!-- All Java AST specific tests live under TreeWalker module. -->
	<module name="TreeWalker">

	<!-- Allow use of comment to suppress javadocstyle -->
	<module name="SuppressionCommentFilter">
	<property name="offCommentFormat" value="CHECKSTYLE.OFF\: ([\w\\|]+)"/>
	<property name="onCommentFormat" value="CHECKSTYLE.ON\: ([\w\\|]+)"/>
	<property name="checkFormat" value="$1"/>
	</module>

	<!--

	FLINK CUSTOM CHECKS

	-->

	<!-- Prohibit T.getT() methods for standard boxed types -->
	<module name="Regexp">
	<property name="format" value="Boolean\.getBoolean"/>
	<property name="illegalPattern" value="true"/>
	<property name="message" value="Use System.getProperties() to get system properties."/>
	</module>

	<module name="Regexp">
	<property name="format" value="Integer\.getInteger"/>
	<property name="illegalPattern" value="true"/>
	<property name="message" value="Use System.getProperties() to get system properties."/>
	</module>

	<module name="Regexp">
	<property name="format" value="Long\.getLong"/>
	<property name="illegalPattern" value="true"/>
	<property name="message" value="Use System.getProperties() to get system properties."/>
	</module>

	<!--

	IllegalImport cannot blacklist classes so we have to fall back to Regexp.

	-->

	<!-- forbid use of commons lang validate -->
	<module name="Regexp">
	<property name="format" value="org\.apache\.commons\.lang3\.Validate"/>
	<property name="illegalPattern" value="true"/>
	<property name="message"
	value="Use Guava Checks instead of Commons Validate. Please refer to the coding guidelines."/>
	</module>
	<!-- forbid the use of google.common.base.Preconditions -->
	<module name="Regexp">
	<property name="format" value="import com\.google\.common\.base\.Preconditions"/>
	<property name="illegalPattern" value="true"/>
	<property name="message"
	value="Use Flink's Preconditions instead of Guava's Preconditions"/>
	</module>
	<!-- forbid the use of com.google.common.annotations.VisibleForTesting -->
	<module name="Regexp">
	<property name="format"
	value="import com\.google\.common\.annotations\.VisibleForTesting"/>
	<property name="illegalPattern" value="true"/>
	<property name="message"
	value="Use Flink's VisibleForTesting instead of Guava's VisibleForTesting"/>
	</module>
	<module name="Regexp">
	<property name="format" value="import static com\.google\.common\.base\.Preconditions"/>
	<property name="illegalPattern" value="true"/>
	<property name="message"
	value="Use Flink's Preconditions instead of Guava's Preconditions"/>
	</module>
	<!-- forbid the use of org.apache.commons.lang.SerializationUtils -->
	<module name="Regexp">
	<property name="format" value="org\.apache\.commons\.lang\.SerializationUtils"/>
	<property name="illegalPattern" value="true"/>
	<property name="message"
	value="Use Flink's InstantiationUtil instead of common's SerializationUtils"/>
	</module>
	<module name="Regexp">
	<property name="format" value="org\.apache\.commons\.lang3\.SerializationUtils"/>
	<property name="illegalPattern" value="true"/>
	<property name="message"
	value="Use Flink's InstantiationUtil instead of common's SerializationUtils"/>
	</module>
	<module name="Regexp">
	<property name="format" value="org\.apache\.commons\.lang\."/>
	<property name="illegalPattern" value="true"/>
	<property name="message" value="Use commons-lang3 instead of commons-lang."/>
	</module>
	<module name="Regexp">
	<property name="format" value="org\.codehaus\.jettison"/>
	<property name="illegalPattern" value="true"/>
	<property name="message" value="Use com.fasterxml.jackson instead of jettison."/>
	</module>
	<module name="Regexp">
	<property name="format" value="org\.testcontainers\.shaded"/>
	<property name="illegalPattern" value="true"/>
	<property name="message" value="Use utilities from appropriate library instead of org.testcontainers."/>
	</module>

	<!-- Enforce Java-style array declarations -->
	<module name="ArrayTypeStyle"/>

	<module name="TodoComment">
	<!-- Checks that disallowed strings are not used in comments. -->
	<property name="format" value="(FIXME)\|(XXX)\|(@author)"/>
	</module>

	<!--

	IMPORT CHECKS

	-->

	<module name="AvoidStarImport">
	<property name="severity" value="error"/>
	</module>

	<module name="IllegalImport">
	<property name="illegalPkgs"
	value="org.mockito, org.powermock"/>
	<message key="import.illegal" value="{0}; Mocking is discouraged. Please refer to the coding guidelines: https://flink.apache.org/how-to-contribute/code-style-and-quality-common/#avoid-mockito---use-reusable-test-implementations."/>
	</module>
	<module name="IllegalImport">
	<property name="illegalPkgs"
	value="autovalue.shaded, avro.shaded, com.google.api.client.repackaged, com.google.appengine.repackaged"/>
	</module>
	<module name="IllegalImport">
	<property name="illegalPkgs" value="org.codehaus.jackson"/>
	<message key="import.illegal" value="{0}; Use flink-shaded-jackson instead."/>
	</module>
	<module name="IllegalImport">
	<property name="illegalPkgs" value="com.jayway.jsonpath"/>
	<message key="import.illegal" value="{0}; Use flink-shaded-jsonpath instead."/>
	</module>
	<module name="IllegalImport">
	<property name="illegalPkgs" value="org.objectweb.asm"/>
	<message key="import.illegal" value="{0}; Use flink-shaded-asm instead."/>
	</module>
	<module name="IllegalImport">
	<property name="illegalPkgs" value="io.netty"/>
	<message key="import.illegal" value="{0}; Use flink-shaded-netty instead."/>
	</module>
	<module name="IllegalImport">
	<property name="illegalPkgs" value="com.google.common"/>
	<message key="import.illegal" value="{0}; Use flink-shaded-guava instead."/>
	</module>

	<module name="RedundantModifier">
	<!-- Checks for redundant modifiers on various symbol definitions.
	See: https://checkstyle.sourceforge.io/checks/modifier/redundantmodifier.html#RedundantModifier

	We exclude METHOD_DEF to allow final methods in final classes to make them more future-proof.
	-->
	<property name="tokens"
	value="VARIABLE_DEF, ANNOTATION_FIELD_DEF, INTERFACE_DEF, CLASS_DEF, ENUM_DEF"/>
	</module>

	<!--
	IllegalImport cannot blacklist classes, and c.g.api.client.util is used for some shaded
	code and some useful code. So we need to fall back to Regexp.
	-->

	<!--
	Require static importing from Preconditions.
	-->
	<module name="RegexpSinglelineJava">
	<property name="format" value="^import com.google.common.base.Preconditions;$"/>
	<property name="message" value="Static import functions from Guava Preconditions"/>
	</module>

	<!--
	The Nullable & Nonnull annotations check.
	-->
	<module name="RegexpSinglelineJava">
	<property name="format" value="^import org.jetbrains.annotations.Nullable;$"/>
	<property name="message" value="Use import javax.annotation.Nullable"/>
	</module>

	<module name="RegexpSinglelineJava">
	<property name="format" value="^import org.jetbrains.annotations.NotNull;$"/>
	<property name="message" value="Use import javax.annotation.Nonnull"/>
	</module>

	<!--

	JAVADOC CHECKS

	-->

	<!-- Checks for Javadoc comments. -->
	<!-- See https://checkstyle.sourceforge.io/checks/javadoc/javadocmethod.html -->
	<module name="JavadocMethod">
	<property name="accessModifiers" value="protected"/>
	<property name="severity" value="error"/>
	<property name="allowMissingParamTags" value="true"/>
	<property name="allowMissingReturnTag" value="true"/>
	</module>

	<!-- Check that paragraph tags are used correctly in Javadoc. -->
	<module name="JavadocParagraph"/>

	<module name="JavadocType">
	<property name="scope" value="protected"/>
	<property name="severity" value="error"/>
	<property name="allowMissingParamTags" value="true"/>
	</module>

	<module name="JavadocStyle">
	<property name="severity" value="error"/>
	<property name="checkHtml" value="true"/>
	</module>

	<!--

	NAMING CHECKS

	-->

	<!-- Item 38 - Adhere to generally accepted naming conventions -->

	<module name="PackageName">
	<!-- Validates identifiers for package names against the
	supplied expression. -->
	<!-- Here the default checkstyle rule restricts package name parts to
	seven characters, this is not in line with common practice at Google.
	-->
	<property name="format" value="^[a-z]+(\.[a-z][a-z0-9]{1,})*$"/>
	<property name="severity" value="error"/>
	</module>

	<module name="TypeNameCheck">
	<!-- Validates static, final fields against the
	expression "^[A-Z][a-zA-Z0-9]*$". -->
	<metadata name="altname" value="TypeName"/>
	<property name="severity" value="error"/>
	</module>

	<module name="ConstantNameCheck">
	<!-- Validates non-private, static, final fields against the supplied
	public/package final fields "^[A-Z][A-Z0-9](_[A-Z0-9]+)$". -->
	<metadata name="altname" value="ConstantName"/>
	<property name="applyToPublic" value="true"/>
	<property name="applyToProtected" value="true"/>
	<property name="applyToPackage" value="true"/>
	<property name="applyToPrivate" value="false"/>
	<property name="format" value="^([A-Z][A-Z0-9](_[A-Z0-9]+)\|FLAG_.*)$"/>
	<message key="name.invalidPattern"
	value="Variable ''{0}'' should be in ALL_CAPS (if it is a constant) or be private (otherwise)."/>
	<property name="severity" value="error"/>
	</module>

	<module name="StaticVariableNameCheck">
	<!-- Validates static, non-final fields against the supplied
	expression "^[a-z][a-zA-Z0-9]*_?$". -->
	<metadata name="altname" value="StaticVariableName"/>
	<property name="applyToPublic" value="true"/>
	<property name="applyToProtected" value="true"/>
	<property name="applyToPackage" value="true"/>
	<property name="applyToPrivate" value="true"/>
	<property name="format" value="^[a-z][a-zA-Z0-9]*_?$"/>
	<property name="severity" value="error"/>
	</module>

	<module name="MemberNameCheck">
	<!-- Validates non-static members against the supplied expression. -->
	<metadata name="altname" value="MemberName"/>
	<property name="applyToPublic" value="true"/>
	<property name="applyToProtected" value="true"/>
	<property name="applyToPackage" value="true"/>
	<property name="applyToPrivate" value="true"/>
	<property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
	<property name="severity" value="error"/>
	</module>

	<module name="MethodNameCheck">
	<!-- Validates identifiers for method names. -->
	<metadata name="altname" value="MethodName"/>
	<property name="format" value="^[a-z][a-zA-Z0-9](_[a-zA-Z0-9]+)$"/>
	<property name="severity" value="error"/>
	</module>

	<module name="ParameterName">
	<!-- Validates identifiers for method parameters against the
	expression "^[a-z][a-zA-Z0-9]*$". -->
	<property name="severity" value="error"/>
	</module>

	<module name="LocalFinalVariableName">
	<!-- Validates identifiers for local final variables against the
	expression "^[a-z][a-zA-Z0-9]*$". -->
	<property name="severity" value="error"/>
	</module>

	<module name="LocalVariableName">
	<!-- Validates identifiers for local variables against the
	expression "^[a-z][a-zA-Z0-9]*$". -->
	<property name="severity" value="error"/>
	</module>

	<!--

	LENGTH and CODING CHECKS

	-->

	<!-- Checks for braces around if and else blocks -->
	<module name="NeedBraces">
	<property name="severity" value="error"/>
	<property name="tokens"
	value="LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO"/>
	</module>

	<module name="UpperEll">
	<!-- Checks that long constants are defined with an upper ell.-->
	<property name="severity" value="error"/>
	</module>

	<module name="FallThrough">
	<!-- Warn about falling through to the next case statement. Similar to
	javac -Xlint:fallthrough, but the check is suppressed if a single-line comment
	on the last non-blank line preceding the fallen-into case contains 'fall through' (or
	some other variants that we don't publicized to promote consistency).
	-->
	<property name="reliefPattern"
	value="fall through\|Fall through\|fallthru\|Fallthru\|falls through\|Falls through\|fallthrough\|Fallthrough\|No break\|NO break\|no break\|continue on"/>
	<property name="severity" value="error"/>
	</module>

	<!-- Checks for over-complicated boolean expressions. -->
	<module name="SimplifyBooleanExpression"/>

	<!-- Detects empty statements (standalone ";" semicolon). -->
	<module name="EmptyStatement"/>

	<!-- Detect multiple consecutive semicolons (e.g. ";;"). -->
	<module name="RegexpSinglelineJava">
	<property name="format" value=";{2,}"/>
	<property name="message" value="Use one semicolon"/>
	<property name="ignoreComments" value="true"/>
	</module>


	<!--

	WHITESPACE CHECKS

	-->

	<module name="EmptyLineSeparator">
	<!-- Checks for empty line separator between tokens. The only
	excluded token is VARIABLE_DEF, allowing class fields to
	be declared on consecutive lines.
	-->
	<property name="allowMultipleEmptyLines" value="false"/>
	<property name="allowMultipleEmptyLinesInsideClassMembers" value="false"/>
	<property name="tokens" value="PACKAGE_DEF, IMPORT, STATIC_IMPORT, CLASS_DEF,
	INTERFACE_DEF, ENUM_DEF, STATIC_INIT, INSTANCE_INIT, METHOD_DEF,
	CTOR_DEF"/>
	</module>
	</module>
	</module>