etc/config/checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--

    Copyright (c) 2010, 2020 Oracle and/or its affiliates. All rights reserved.

    This program and the accompanying materials are made available under the
    terms of the Eclipse Public License v. 2.0, which is available at
    http://www.eclipse.org/legal/epl-2.0.

    This Source Code may also be made available under the following Secondary
    Licenses when the conditions for such availability set forth in the
    Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
    version 2 with the GNU Classpath Exception, which is available at
    https://www.gnu.org/software/classpath/license.html.

    SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0

-->

<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN" "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<!--
    This file is based on maven-checkstyle-plugin config/sun_checks.xml file.

    Checkstyle configuration that checks the coding conventions based on:

      - 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 custom relaxations of the rules above & 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">
    <!--
        If you set the basedir property below, then all reported file
        names will be relative to the specified directory. See
        http://checkstyle.sourceforge.net/5.x/config.html#Checker

        <property name="basedir" value="${basedir}"/>
    -->
    <property name="charset" value="UTF-8"/>
    <property name="cacheFile" value="${checkstyle.cache.file}"/>

    <!-- Checks that each Java package has a Javadoc file used for commenting. -->
    <!-- See http://checkstyle.sf.net/config_javadoc.html#JavadocPackage       -->
    <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"/>

    <module name="FileLength"/>

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

    <!-- Present in checkstyle-verify.xml -->
    <!--<module name="FileTabCharacter">
        <property name="eachLine" value="true"/>
    </module>-->

    <!-- Present in checkstyle-verify.xml -->
    <!--<module name="RegexpSingleline">
        <property name="format" value="\S+\s+$"/>
        <property name="message" value="Non-empty line has trailing spaces."/>
    </module>-->

    <module name="TreeWalker">
        <property name="tabWidth" value="4"/>

        <!-- Checks for Javadoc comments.                     -->
        <!-- See http://checkstyle.sf.net/config_javadoc.html -->
        <module name="JavadocMethod">
            <property name="scope" value="protected"/>
        <!-- <property name="allowUndeclaredRTE" value="true"/>-->
        </module>
        <module name="JavadocType">
            <property name="scope" value="protected"/>
        </module>
        <module name="JavadocVariable">
            <property name="scope" value="protected"/>
        </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> -->

        <!-- Checks for imports                              -->
        <!-- See http://checkstyle.sf.net/config_import.html -->
        <module name="IllegalImport"/> <!-- defaults to sun.* packages -->
        <!-- Present in checkstyle-verify.xml -->
        <!--<module name="AvoidStarImport"/>-->
        <module name="RedundantImport"/>
        <!-- Present in checkstyle-verify.xml -->
        <!--<module name="UnusedImports"/>-->

        <!-- Checks for Size Violations.                    -->
        <!-- See http://checkstyle.sf.net/config_sizes.html -->
        <!-- Present in checkstyle-verify.xml -->
        <!--<module name="LineLength">
            <property name="max" value="130"/>
            <property name="ignorePattern" value="@version|@see|@todo|TODO"/>
        </module>-->
        <module name="MethodLength"/>
        <module name="ParameterNumber"/>

        <!-- Checks for whitespace                               -->
        <!-- See http://checkstyle.sf.net/config_whitespace.html -->
        <module name="EmptyForIteratorPad"/>
        <module name="OperatorWrap"/>
        <!-- Present in checkstyle-verify.xml -->
        <!--<module name="MethodParamPad"/>
        <module name="NoWhitespaceAfter"/>
        <module name="NoWhitespaceBefore"/>
        <module name="ParenPad"/>
        <module name="TypecastParenPad"/>
        <module name="WhitespaceAfter"/>
        <module name="WhitespaceAround">
            <property name="allowEmptyConstructors" value="true"/>
        </module>-->

        <!-- Modifier Checks                                    -->
        <!-- See http://checkstyle.sf.net/config_modifiers.html -->
        <!--<module name="ModifierOrder"/>-->
        <module name="RedundantModifier"/>

        <!-- Checks for blocks. You know, those {}'s         -->
        <!-- See http://checkstyle.sf.net/config_blocks.html -->
        <module name="AvoidNestedBlocks"/>
        <!-- Present in checkstyle-verify.xml -->
        <!--<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="MagicNumber">
            <property name="ignoreHashCodeMethod" value="true"/>
        </module>
        <module name="MissingSwitchDefault"/>

        <!-- TODO: Ignoring module until this bug is resolved: https://jira.codehaus.org/browse/MCHECKSTYLE-271 -->
        <!--<module name="RedundantThrows">
            <property name="allowUnchecked" value="true"/>
        </module>-->

        <module name="RedundantModifier">
            <property name="tokens" value="INTERFACE_DEF"/>
        </module>
        <module name="SimplifyBooleanExpression"/>
        <module name="SimplifyBooleanReturn"/>

        <!-- Checks for class design                         -->
        <!-- See http://checkstyle.sf.net/config_design.html -->
        <module name="DesignForExtension"/>
        <module name="FinalClass"/>
        <module name="HideUtilityClassConstructor"/>
        <module name="InterfaceIsType"/>
        <module name="VisibilityModifier"/>
        <module name="ThrowsCount">
            <property name="max" value="3"/>
        </module>

        <!-- Miscellaneous other checks.                   -->
        <!-- See http://checkstyle.sf.net/config_misc.html -->
        <module name="ArrayTypeStyle"/>
        <module name="FinalParameters"/>
        <module name="TodoComment"/>
        <!-- Present in checkstyle-verify.xml -->
        <!--<module name="UpperEll"/>-->
    </module>
</module>