checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.2//EN" "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">
<module name="Checker">
    <property name="charset" value="UTF-8"/>
    <property name="fileExtensions" value="java"/>
    <property name="localeLanguage" value="en"/>
    <property name="localeCountry" value="US"/>

    <module name="NewlineAtEndOfFile"/>

    <!-- disallow trailing whitespace -->
    <module name="RegexpSingleline">
        <property name="format" value="\s+$"/>
        <property name="message" value="trailing whitespace"/>
    </module>

    <!-- note: RegexpMultiline shows nicer messages than Regexp, but has to be outside TreeWalker -->
    <!-- disallow multiple consecutive blank lines -->
    <module name="RegexpMultiline">
        <property name="format" value="\n[\t ]*\r?\n[\t ]*\r?\n"/>
        <property name="message" value="adjacent blank lines"/>
    </module>

    <!-- disallow blank after { -->
    <module name="RegexpMultiline">
        <property name="format" value="\{[\t ]*\r?\n[\t ]*\r?\n"/>
        <property name="message" value="blank line after '{'"/>
    </module>

    <!-- disallow blank before } -->
    <module name="RegexpMultiline">
        <property name="format" value="\n[\t ]*\r?\n[\t ]*\}"/>
        <property name="message" value="blank line before '}'"/>
    </module>

    <!-- require blank before { in the same indentation level -->
    <module name="RegexpMultiline">
        <!-- the regex works as follows:
        It matches (=fails) for \n<indentation><something>\n<same indentation><control statement>[...]{\n
        while <something> is a single line comment, it'll look for a blank line one line earlier
        if <something> is a space, indicating a formatting error or ' */', it'll ignore the instance
        if <something> is a tab, indicating a continued line, it'll ignore the instance
        <control statement> is 'if', 'do', 'while', 'for', 'try' or nothing (instance initializer block)

        - first \n: with positive lookbehind (?<=\n) to move the error marker to a more reasonable place
        - capture tabs for <indentation>, later referenced via \1
        - remaining preceding line as a non-comment (doesn't start with '/', '//', ' ' or '\t') or multiple lines where all but the first are a single line comment with the same indentation
        - new line
        - <indentation> as captured earlier
        - <control statement> as specified above
        - { before the next new line -->
        <property name="format" value="(?&lt;=\n)([\t]+)(?:[^/\r\n \t][^\r\n]*|/[^/\r\n][^\r\n]*|[^/\r\n][^\r\n]*(\r?\n\1//[^\r\n]*)+)\r?\n\1(|(if|do|while|for|try)[^\r\n]+)\{[\t ]*\r?\n"/>
        <property name="message" value="missing blank line before block at same indentation level"/>
    </module>

    <!-- require blank after } in the same indentation level -->
    <module name="RegexpMultiline">
        <!-- \n<indentation>}\n<same indentation><whatever unless newline, '}' or starting with cas(e) or def(ault)> -->
        <property name="format" value="(?&lt;=\n)([\t]+)\}\r?\n\1(?:[^\r\n\}cd]|c[^\r\na]|ca[^\r\ns]|d[^\r\ne]|de[^\r\nf])"/>
        <property name="message" value="missing blank line after block at same indentation level"/>
    </module>

    <module name="TreeWalker">
        <!-- Ensure all imports are ship shape -->
        <module name="AvoidStarImport"/>
        <module name="IllegalImport"/>
        <module name="RedundantImport"/>
        <module name="UnusedImports"/>

        <module name="ImportOrder">
            <property name="groups" value="java,javax,*,net.minecraft,net.fabricmc"/>
            <property name="ordered" value="false"/><!-- the plugin orders alphabetically without considering separators.. -->
            <property name="separated" value="true"/>
            <property name="option" value="top"/>
            <property name="sortStaticImportsAlphabetically" value="true"/>
        </module>

        <!-- Ensures braces are at the end of a line -->
        <module name="LeftCurly"/>
        <module name="RightCurly"/>

        <!-- single line statements on one line, -->
        <module name="NeedBraces">
            <property name="tokens" value="LITERAL_IF,LITERAL_FOR,LITERAL_WHILE"/>
            <property name="allowSingleLineStatement" value="true"/>
        </module>
        <module name="NeedBraces">
            <property name="tokens" value="LITERAL_ELSE,LITERAL_DO"/>
            <property name="allowSingleLineStatement" value="false"/>
        </module>

        <module name="EmptyLineSeparator">
            <property name="allowNoEmptyLineBetweenFields" value="true"/>
            <property name="allowMultipleEmptyLines" value="false"/>
            <!-- exclude  METHOD_DEF and VARIABLE_DEF -->
            <property name="tokens" value="PACKAGE_DEF,IMPORT,STATIC_IMPORT,CLASS_DEF,INTERFACE_DEF,ENUM_DEF,STATIC_INIT,INSTANCE_INIT,CTOR_DEF"/>
        </module>

        <module name="OperatorWrap"/>
        <module name="SeparatorWrap">
            <property name="tokens" value="DOT,ELLIPSIS,AT"/>
            <property name="option" value="nl"/>
        </module>
        <module name="SeparatorWrap">
            <property name="tokens" value="COMMA,SEMI"/>
            <property name="option" value="eol"/>
        </module>

        <module name="Indentation">
            <property name="basicOffset" value="8"/>
            <property name="caseIndent" value="0"/>
            <property name="throwsIndent" value="8"/>
            <property name="arrayInitIndent" value="8"/>
            <property name="lineWrappingIndentation" value="16"/>
        </module>

        <module name="ParenPad"/>
        <module name="NoWhitespaceBefore"/>
        <module name="NoWhitespaceAfter">
            <!-- allow ARRAY_INIT -->
            <property name="tokens" value="AT,INC,DEC,UNARY_MINUS,UNARY_PLUS,BNOT,LNOT,DOT,ARRAY_DECLARATOR,INDEX_OP"/>
        </module>
        <module name="WhitespaceAfter"/>
        <module name="WhitespaceAround">
            <!-- Allow PLUS, MINUS, MUL, DIV as they may be more readable without spaces in some cases -->
            <property name="tokens" value="ASSIGN,BAND,BAND_ASSIGN,BOR,BOR_ASSIGN,BSR,BSR_ASSIGN,BXOR,BXOR_ASSIGN,COLON,DIV_ASSIGN,DO_WHILE,EQUAL,GE,GT,LAMBDA,LAND,LCURLY,LE,LITERAL_CATCH,LITERAL_DO,LITERAL_ELSE,LITERAL_FINALLY,LITERAL_FOR,LITERAL_IF,LITERAL_RETURN,LITERAL_SWITCH,LITERAL_SYNCHRONIZED,LITERAL_TRY,LITERAL_WHILE,LOR,LT,MINUS_ASSIGN,MOD,MOD_ASSIGN,NOT_EQUAL,PLUS_ASSIGN,QUESTION,RCURLY,SL,SLIST,SL_ASSIGN,SR,SR_ASSIGN,STAR,STAR_ASSIGN,LITERAL_ASSERT,TYPE_EXTENSION_AND"/>
        </module>
        <module name="SingleSpaceSeparator"/>
        <module name="GenericWhitespace"/>
        <module name="CommentsIndentation"/>

        <module name="ArrayTypeStyle"/>
        <module name="DefaultComesLast">
            <property name="skipIfLastAndSharedWithCase" value="true"/>
        </module>
        <module name="SimplifyBooleanExpression"/>
        <module name="SimplifyBooleanReturn"/>
        <module name="StringLiteralEquality"/>

        <module name="ModifierOrder"/>
        <module name="RedundantModifier"/>

        <module name="AnnotationLocation"/>
        <module name="MissingOverride"/>

        <!-- By default this allows catch blocks with only comments -->
        <module name="EmptyCatchBlock"/>

        <!-- Enforce tabs -->
        <module name="RegexpSinglelineJava">
            <property name="format" value="^\t* ([^*]|\*[^ /])"/>
            <property name="message" value="non-tab indentation"/>
        </module>

        <module name="OuterTypeFilename"/>

        <!--<module name="InvalidJavadocPosition"/>-->
        <module name="JavadocParagraph"/>
        <module name="JavadocStyle"/>
        <module name="AtclauseOrder">
            <property name="tagOrder" value="@param,@return,@throws,@deprecated"/>
        </module>
    </module>
</module>