Paper/paper-api/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">
    <!-- See http://checkstyle.sourceforge.net/config_misc.html#NewlineAtEndOfFile -->
    <module name="NewlineAtEndOfFile">
        <property name="lineSeparator" value="lf_cr_crlf"/>
    </module>

    <!-- See http://checkstyle.sourceforge.net/config_whitespace.html -->
    <module name="FileTabCharacter"/>

    <!-- See http://checkstyle.sourceforge.net/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>

    <!-- See https://checkstyle.sourceforge.io/config_javadoc.html#JavadocPackage-->
    <module name="JavadocPackage"/>

    <module name="SuppressionSingleFilter">
        <property name="message" value="'(implNote|implSpec|apiNote)'\."/>
    </module>
    <!-- Don't check for missing package-info in tests -->
    <module name="SuppressionSingleFilter">
        <property name="checks" value="JavadocPackage"/>
        <property name="files" value=".*[\\/]src[\\/]test[\\/].*\.java$"/>
    </module>

    <module name="TreeWalker">
        <!-- See https://checkstyle.org/config_javadoc.html -->
        <module name="AtclauseOrder"/>
        <module name="InvalidJavadocPosition"/>
        <module name="JavadocBlockTagLocation"/>
        <module name="JavadocContentLocationCheck"/>
        <module name="JavadocMethod"/>
        <module name="JavadocType"/>
        <module name="MissingJavadocPackage"/>
        <module name="NonEmptyAtclauseDescription"/>

        <!-- See http://checkstyle.sourceforge.net/config_filters.html -->
        <module name="SuppressionCommentFilter"/>

        <!-- See http://checkstyle.sourceforge.net/config_imports.html -->
        <module name="AvoidStarImport">
            <property name="allowStaticMemberImports" value="true"/>
        </module>
        <module name="ImportOrder">
            <property name="option" value="above"/>
            <property name="ordered" value="true"/>
            <property name="separatedStaticGroups" value="true"/>
            <property name="sortStaticImportsAlphabetically" value="true"/>
        </module>
        <module name="RedundantImport"/>
        <module name="UnusedImports"/>

        <!-- See https://checkstyle.org/config_whitespace.html -->
        <module name="GenericWhitespace"/>
        <module name="MethodParamPad"/>
        <module name="NoLineWrap"/>
        <module name="NoWhitespaceAfter"/>
        <module name="NoWhitespaceBefore">
            <property name="allowLineBreaks" value="true"/>
        </module>
        <module name="OperatorWrap"/>
        <module name="ParenPad"/>
        <module name="SingleSpaceSeparator"/>
        <module name="TypecastParenPad"/>
        <module name="WhitespaceAfter"/>
        <module name="WhitespaceAround">
            <property name="allowEmptyCatches" value="true"/>
            <property name="allowEmptyConstructors" value="true"/>
            <property name="allowEmptyMethods" value="true"/>
            <property name="allowEmptyTypes" value="true"/>
        </module>

        <!-- See http://checkstyle.sourceforge.net/config_modifiers.html -->
        <module name="ModifierOrder"/>

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

        <!-- See http://checkstyle.sourceforge.net/config_design.html -->
        <module name="FinalClass"/>

        <!-- See http://checkstyle.sourceforge.net/config_misc.html -->
        <module name="ArrayTypeStyle"/>
        <module name="UpperEll"/>
    </module>
</module>