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">
    <property name="charset" value="UTF-8"/>
    <property name="fileExtensions" value="java"/>

    <!-- ======================================== -->
    <!-- Annotations -->
    <!-- ======================================== -->

    <module name="TreeWalker">
        <module name="AnnotationLocation"/>
        <module name="AnnotationUseStyle"/>
        <module name="PackageAnnotation"/>
        <module name="SuppressWarnings"/>
    </module>

    <!-- ======================================== -->
    <!-- Blocks -->
    <!-- ======================================== -->

    <module name="TreeWalker">
        <module name="AvoidNestedBlocks"/>
        <module name="EmptyBlock"/>
        <module name="EmptyCatchBlock"/>

        <module name="NeedBraces">
            <property name="allowSingleLineStatement" value="true"/>
            <property name="allowEmptyLoopBody" value="true"/>
        </module>

        <module name="LeftCurly">
            <property name="option" value="nlow"/>
        </module>

        <module name="RightCurly">
            <property name="option" value="same"/>
        </module>
    </module>

    <!-- ======================================== -->
    <!-- Class Design -->
    <!-- ======================================== -->

    <module name="TreeWalker">
        <module name="FinalClass"/>
        <module name="HideUtilityClassConstructor"/>
        <module name="InnerTypeLast"/>
        <module name="MutableException"/>
        <module name="OneTopLevelClass"/>

        <module name="VisibilityModifier">
            <property name="allowPublicFinalFields" value="true"/>
        </module>
    </module>

    <!-- ======================================== -->
    <!-- Whitespace -->
    <!-- ======================================== -->

    <module name="FileTabCharacter"/>

    <module name="TreeWalker">
        <module name="EmptyForInitializerPad"/>
        <module name="EmptyForIteratorPad"/>
        <module name="GenericWhitespace"/>
        <module name="MethodParamPad"/>
        <module name="ParenPad"/>
        <module name="SingleSpaceSeparator"/>
        <module name="TypecastParenPad"/>
        <module name="WhitespaceAfter"/>
        <module name="WhitespaceAround"/>
        <module name="OperatorWrap"/>
        <module name="NoLineWrap"/>

        <module name="SeparatorWrap">
            <property name="option" value="eol"/>
            <property name="tokens"
                      value="COMMA, SEMI, ELLIPSIS, LPAREN, RPAREN, ARRAY_DECLARATOR, METHOD_REF"/>
        </module>

        <module name="NoWhitespaceAfter">
            <property name="allowLineBreaks" value="false"/>
            <property name="tokens"
                      value="ARRAY_INIT, AT, INC, DEC, UNARY_MINUS, UNARY_PLUS, BNOT, LNOT, DOT, ARRAY_DECLARATOR, INDEX_OP, METHOD_REF"/>
        </module>

        <module name="NoWhitespaceBefore">
            <property name="allowLineBreaks" value="true"/>
            <property name="tokens"
                      value="COMMA, SEMI, POST_INC, POST_DEC, DOT, GENERIC_END, ELLIPSIS, METHOD_REF"/>
        </module>

        <module name="EmptyLineSeparator">
            <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 name="VisibilityModifier">
            <property name="packageAllowed" value="true" />
            <property name="protectedAllowed" value="true" />
            <property name="allowPublicFinalFields" value="true" />
        </module>
    </module>
</module>