hadoop/hadoop-build-tools/src/main/resources/checkstyle/checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
    "-//Checkstyle//DTD Checkstyle Configuration 1.2//EN"
    "https://checkstyle.org/dtds/configuration_1_2.dtd">

<!--
   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.
-->
<!--

  Checkstyle configuration for Hadoop that is based on the sun_checks.xml file
  that is bundled with Checkstyle and includes checks for:

    - the Java Language Specification at
      http://java.sun.com/docs/books/jls/second_edition/html/index.html

    - the Sun Code Conventions at http://java.sun.com/docs/codeconv/

    - the Javadoc guidelines at
      http://java.sun.com/j2se/javadoc/writingdoccomments/index.html

    - the JDK Api documentation http://java.sun.com/j2se/docs/api/index.html

    - some best practices

  Checkstyle is very configurable. Be sure to read the documentation at
  http://checkstyle.sf.net (or in your downloaded distribution).

  Most Checks are configurable, be sure to consult the documentation.

  To completely disable a check, just comment it out or delete it from the file.

  Finally, it is worth reading the documentation.

-->

<module name="Checker">

    <module name="SuppressWarningsFilter"/>

    <!-- Checks that a package.html file exists for each package.     -->
    <!-- See http://checkstyle.sf.net/config_javadoc.html#PackageHtml -->
    <module name="JavadocPackage"/>

    <!-- Checks whether files end with a new line.                        -->
    <!-- See http://checkstyle.sf.net/config_misc.html#NewlineAtEndOfFile -->
    <!-- module name="NewlineAtEndOfFile"/-->

    <!-- Checks that property files contain the same keys.         -->
    <!-- See http://checkstyle.sf.net/config_misc.html#Translation -->
    <module name="Translation"/>

    <!-- We have many existing long files, this check ends up being spurious -->
    <!--<module name="FileLength">-->
    <module name="FileTabCharacter"/>

    <!-- Checks for line length violations.                                 -->
    <!-- See https://checkstyle.sourceforge.io/config_sizes.html#LineLength -->
    <module name="LineLength">
        <property name="max" value="100"/>
    </module>

    <module name="TreeWalker">

        <module name="SuppressWarningsHolder"/>
        <module name="SuppressionCommentFilter"/>
        <module name="SuppressWithNearbyCommentFilter"/>


        <!-- Checks for Javadoc comments.                     -->
        <!-- See http://checkstyle.sf.net/config_javadoc.html -->
        <module name="JavadocType">
          <property name="scope" value="public"/>
          <property name="allowMissingParamTags" value="true"/>
        </module>
        <module name="JavadocStyle"/>

        <!-- Checks for Naming Conventions.                  -->
        <!-- See http://checkstyle.sf.net/config_naming.html -->
        <module name="ConstantName"/>
        <module name="LocalFinalVariableName"/>
        <module name="LocalVariableName"/>
        <module name="MemberName"/>
        <module name="MethodName"/>
        <module name="PackageName"/>
        <module name="ParameterName"/>
        <module name="StaticVariableName"/>
        <module name="TypeName"/>


        <!-- Checks for Headers                                -->
        <!-- See http://checkstyle.sf.net/config_header.html   -->
        <!-- <module name="Header">                            -->
            <!-- The follow property value demonstrates the ability     -->
            <!-- to have access to ANT properties. In this case it uses -->
            <!-- the ${basedir} property to allow Checkstyle to be run  -->
            <!-- from any directory within a project. See property      -->
            <!-- expansion,                                             -->
            <!-- http://checkstyle.sf.net/config.html#properties        -->
            <!-- <property                                              -->
            <!--     name="headerFile"                                  -->
            <!--     value="${basedir}/java.header"/>                   -->
        <!-- </module> -->

        <!-- Following interprets the header file as regular expressions. -->
        <!-- <module name="RegexpHeader"/>                                -->


        <!-- Checks for imports                              -->
        <!-- See http://checkstyle.sf.net/config_import.html -->
        <module name="IllegalImport">
            <property name="regexp" value="true"/>
            <property name="illegalPkgs" value="sun"/>
        </module>
        <module name="RedundantImport"/>
        <module name="UnusedImports"/>


        <!-- Checks for Size Violations.                    -->
        <!-- See http://checkstyle.sf.net/config_sizes.html -->
        <module name="MethodLength"/>
        <module name="ParameterNumber">
          <property name="ignoreOverriddenMethods" value="true"/>
        </module>


        <!-- Checks for whitespace                               -->
        <!-- See http://checkstyle.sf.net/config_whitespace.html -->
        <module name="EmptyForIteratorPad"/>
        <module name="MethodParamPad"/>
        <module name="NoWhitespaceAfter"/>
        <module name="NoWhitespaceBefore"/>
        <module name="ParenPad"/>
        <module name="TypecastParenPad"/>
        <module name="WhitespaceAfter">
          <property name="tokens" value="COMMA, SEMI"/>
        </module>


        <!-- Modifier Checks                                    -->
        <!-- See http://checkstyle.sf.net/config_modifiers.html -->
        <!-- This one is nitty, disable -->
        <!-- <module name="ModifierOrder"/> -->
        <module name="RedundantModifier"/>


        <!-- Checks for blocks. You know, those {}'s         -->
        <!-- See http://checkstyle.sf.net/config_blocks.html -->
        <module name="AvoidNestedBlocks">
          <property name="allowInSwitchCase" value="true"/>
        </module>
        <module name="EmptyBlock"/>
        <module name="LeftCurly"/>
        <module name="NeedBraces"/>
        <module name="RightCurly"/>


        <!-- Checks for common coding problems               -->
        <!-- See http://checkstyle.sf.net/config_coding.html -->
        <!-- module name="AvoidInlineConditionals"/-->
        <module name="EmptyStatement"/>
        <module name="EqualsHashCode"/>
        <module name="HiddenField">
          <property name="ignoreConstructorParameter" value="true"/>
          <property name="ignoreSetter" value="true"/>
        </module>
        <module name="IllegalInstantiation"/>
        <module name="InnerAssignment"/>
        <module name="MissingSwitchDefault"/>
        <module name="SimplifyBooleanExpression"/>
        <module name="SimplifyBooleanReturn"/>

        <!-- Checks for class design                         -->
        <!-- See http://checkstyle.sf.net/config_design.html -->
        <module name="FinalClass"/>
        <module name="HideUtilityClassConstructor"/>
        <module name="InterfaceIsType"/>
        <module name="VisibilityModifier"/>


        <!-- Miscellaneous other checks.                   -->
        <!-- See http://checkstyle.sf.net/config_misc.html -->
        <module name="ArrayTypeStyle"/>
        <module name="Indentation">
            <property name="basicOffset" value="2" />
            <property name="caseIndent" value="0" />
        </module>
        <!--<module name="TodoComment"/>-->
        <module name="UpperEll"/>

    </module>

</module>