checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
          "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
    <!--
        If you set the basedir property below, then all reported file
        names will be relative to the specified directory. See
        https://checkstyle.org/5.x/config.html#Checker

        <property name="basedir" value="${basedir}"/>
    -->
    <property name="severity" value="error"/>

    <property name="fileExtensions" value="java, properties, xml"/>

    <!-- Excludes all 'module-info.java' files              -->
    <!-- See https://checkstyle.org/config_filefilters.html -->
    <module name="BeforeExecutionExclusionFileFilter">
        <property name="fileNamePattern" value="module\-info\.java$"/>
    </module>

    <!-- https://checkstyle.org/config_filters.html#SuppressionFilter -->
    <module name="SuppressionFilter">
        <property name="file" value="${org.checkstyle.sun.suppressionfilter.config}"
                  default="checkstyle-suppressions.xml" />
        <property name="optional" value="true"/>
    </module>

    <!-- Checks that a package-info.java file exists for each package.     -->
    <!-- See https://checkstyle.org/config_javadoc.html#JavadocPackage -->
    <!--<module name="JavadocPackage"/>-->

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

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

    <!-- Checks for Size Violations.                    -->
    <!-- See https://checkstyle.org/config_sizes.html -->
    <module name="FileLength"/>
    <module name="LineLength">
      <property name="max" value="100"/>
      <property name="fileExtensions" value="java"/>
    </module>

    <!-- Checks for whitespace                               -->
    <!-- See https://checkstyle.org/config_whitespace.html -->
    <module name="FileTabCharacter"/>

    <!-- Miscellaneous other checks.                   -->
    <!-- See https://checkstyle.org/config_misc.html -->
    <module name="RegexpSingleline">
       <property name="format" value="\s+$"/>
       <property name="minimum" value="0"/>
       <property name="maximum" value="0"/>
       <property name="message" value="Line has trailing spaces."/>
    </module>

    <!-- Checks for Headers                                -->
    <!-- See https://checkstyle.org/config_header.html   -->
    <!-- <module name="Header"> -->
    <!--   <property name="headerFile" value="${checkstyle.header.file}"/> -->
    <!--   <property name="fileExtensions" value="java"/> -->
    <!-- </module> -->

    <module name="SuppressWarningsFilter" />

    <module name="TreeWalker">
        <!-- Checks for Javadoc comments.                     -->
        <!-- See https://checkstyle.org/config_javadoc.html -->
        <module name="InvalidJavadocPosition"/>
        <module name="JavadocMethod"/>
        <module name="JavadocType"/>
        <!--<module name="JavadocVariable"/>-->
        <module name="JavadocStyle"/>
        <!--<module name="MissingJavadocMethod"/>-->

        <!-- Checks for Naming Conventions.                  -->
        <!-- See https://checkstyle.org/config_naming.html -->
        <module name="ConstantName"/>
        <module name="LocalFinalVariableName"/>
        <module name="LocalVariableName"/>
        <module name="MemberName">
            <property name="format" value="^(TAG|DEBUG|[a-z][a-zA-Z0-9]*)$"/>
        </module>
        <module name="MethodName"/>
        <module name="PackageName"/>
        <module name="ParameterName"/>
        <module name="StaticVariableName"/>
        <module name="TypeName"/>

        <!-- Checks for imports                              -->
        <!-- See https://checkstyle.org/config_import.html -->
        <module name="AvoidStarImport"/>
        <module name="IllegalImport"/> <!-- defaults to sun.* packages -->
        <module name="RedundantImport"/>
        <module name="UnusedImports"/>

        <!-- Checks for Size Violations.                    -->
        <!-- See https://checkstyle.org/config_sizes.html -->
        <module name="MethodLength">
            <property name="severity" value="warning"/>
        </module>
        <module name="ParameterNumber">
            <property name="severity" value="warning"/>
        </module>

        <!-- Checks for whitespace                               -->
        <!-- See https://checkstyle.org/config_whitespace.html -->
        <module name="EmptyForIteratorPad"/>
        <module name="GenericWhitespace"/>
        <module name="MethodParamPad"/>
        <module name="NoWhitespaceAfter"/>
        <module name="NoWhitespaceBefore"/>
        <module name="OperatorWrap"/>
        <module name="ParenPad"/>
        <module name="TypecastParenPad"/>
        <module name="WhitespaceAfter"/>
        <module name="WhitespaceAround"/>

        <!-- Modifier Checks                                    -->
        <!-- See https://checkstyle.org/config_modifiers.html -->
        <module name="ModifierOrder"/>
        <module name="RedundantModifier"/>

        <!-- Checks for blocks. You know, those {}'s         -->
        <!-- See https://checkstyle.org/config_blocks.html -->
        <module name="AvoidNestedBlocks"/>
        <module name="EmptyBlock"/>
        <module name="LeftCurly"/>
        <module name="NeedBraces"/>
        <module name="RightCurly"/>

        <!-- Checks for common coding problems               -->
        <!-- See https://checkstyle.org/config_coding.html -->
        <module name="EmptyStatement"/>
        <module name="EqualsHashCode">
            <property name="severity" value="warning"/>
        </module>
        <module name="HiddenField">
            <property name="ignoreConstructorParameter" value="true"/>
            <property name="ignoreSetter" value="true"/>
        </module>
        <module name="IllegalInstantiation"/>
        <module name="InnerAssignment"/>
        <!--<module name="MagicNumber"/>-->
        <!--<module name="MissingSwitchDefault">
            <property name="severity" value="warning"/>
        </module>-->
        <module name="MultipleVariableDeclarations"/>
        <module name="SimplifyBooleanExpression"/>
        <module name="SimplifyBooleanReturn"/>
        <module name="FinalLocalVariable">
            <property name="tokens" value="VARIABLE_DEF,PARAMETER_DEF"/>
            <property name="validateEnhancedForLoopVariable" value="true"/>
        </module>

        <!-- Checks for class design                         -->
        <!-- See https://checkstyle.org/config_design.html -->
        <!--<module name="DesignForExtension"/>-->
        <module name="FinalClass"/>
        <module name="HideUtilityClassConstructor"/>
        <module name="InterfaceIsType"/>
        <!--<module name="VisibilityModifier">
            <property name="ignoreAnnotationCanonicalNames" value="State,ColumnInfo"/>
            <property name="severity" value="warning"/>
        </module>-->

        <!-- Miscellaneous other checks.                   -->
        <!-- See https://checkstyle.org/config_misc.html -->
        <module name="ArrayTypeStyle"/>
        <module name="FinalParameters"/>
        <!--<module name="TodoComment">
            <property name="format" value="(TODO:|FIXME:)"/>
            <property name="severity" value="warning"/>
        </module>-->
        <module name="UpperEll"/>

        <module name="SuppressWarningsHolder" />

        <!-- https://checkstyle.org/config_filters.html#SuppressionXpathFilter -->
        <module name="SuppressionXpathFilter">
            <property name="file" value="${org.checkstyle.sun.suppressionxpathfilter.config}"
                      default="checkstyle-xpath-suppressions.xml" />
            <property name="optional" value="true"/>
        </module>
    </module>
</module>