checkstyle.xml

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

<!DOCTYPE module PUBLIC "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN" "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
    <module name="SuppressWarningsFilter"/>

    <!-- See https://checkstyle.org/config_misc.html#NewlineAtEndOfFile -->
    <module name="NewlineAtEndOfFile"/>

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

    <!-- See https://checkstyle.org/config_sizes.html -->
    <module name="LineLength">
        <property name="max" value="120"/>
    </module>

    <!-- 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>

    <module name="TreeWalker">
        <module name="SuppressWarningsHolder"/>

        <!-- See https://checkstyle.org/config_naming.html -->
        <module name="ConstantName"/>
        <module name="LocalFinalVariableName"/>
        <module name="LocalVariableName"/>
        <module name="MemberName"/>
        <module name="MethodName"/>
        <module name="PackageName">
            <!-- sonar doesn't like underscores and uppercase letters -->
            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
        </module>
        <module name="PackageName"/>
        <module name="ParameterName"/>
        <module name="StaticVariableName"/>

        <!-- See https://checkstyle.org/config_imports.html -->
        <module name="AvoidStarImport"/>
        <module name="RedundantImport"/>
        <module name="UnusedImports">
            <property name="processJavadoc" value="false"/>
        </module>

        <!-- 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">
            <property name="option" value="eol"/>
        </module>
        <module name="ParenPad"/>
        <module name="TypecastParenPad"/>

        <!-- See https://checkstyle.org/config_blocks.html -->
        <module name="AvoidNestedBlocks"/>
        <module name="EmptyBlock"/>
        <module name="LeftCurly"/>
        <module name="NeedBraces"/>
        <module name="RightCurly"/>

        <!-- See https://checkstyle.org/config_coding.html -->
        <module name="EmptyStatement"/>
        <module name="EqualsHashCode"/>
        <module name="IllegalInstantiation"/>
        <module name="InnerAssignment"/>
        <module name="MissingSwitchDefault"/>
        <module name="MultipleVariableDeclarations"/>
        <module name="SimplifyBooleanExpression"/>
        <module name="SimplifyBooleanReturn"/>

        <!-- See https://checkstyle.org/config_misc.html -->
        <module name="ArrayTypeStyle"/>
        <module name="FinalParameters"/>
        <module name="TodoComment"/>
        <module name="UpperEll"/>
    </module>
</module>