vks-java/config/checkstyle/checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
SPDX-FileCopyrightText: 2021 Paul Schaub <info@pgpainless.org>

SPDX-License-Identifier: CC0-1.0
-->

<!DOCTYPE module PUBLIC
        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
        "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<module name="Checker">

    <!-- Suppressions -->
    <module name="SuppressionFilter">
        <property name="file" value="${config_loc}/suppressions.xml"/>
    </module>

    <module name="NewlineAtEndOfFile">
        <property name="lineSeparator" value="lf"/>
    </module>

    <module name="RegexpSingleline">
        <!--
            Matches StringBuilder.append(String) calls where the
            argument is a String of length one. Those should be replaced
            with append(char) for performance reasons.

            TODO: This could be more advanced in order to match also
            - .append("\u1234")
        -->
        <property name="format" value="\.append\(&quot;(.|\\.)&quot;\)"/>
        <property name="message" value="Don&apos;t use StringBuilder.append(String) when you can use StringBuilder.append(char). Solution: Replace double quotes of append&apos;s argument with single quotes."/>
    </module>

    <!-- Whitespace only lines -->
    <module name="RegexpSingleline">
        <property name="format" value="^\s+$"/>
        <property name="message" value="Line containing only whitespace character(s)"/>
    </module>

    <!-- Mixed spaces/tabs -->
    <module name="RegexpSingleline">
        <!-- We use {2,} instead of + here to address the typical case where a file was written
           with tabs but javadoc is causing '\t *' -->
        <property name="format" value="^\t+ {2,}"/>
        <property name="message" value="Line containing space(s) after tab(s)"/>
    </module>

    <!-- Trailing whitespaces -->
    <module name="RegexpSingleline">
        <!--
            Explaining the following Regex

                       \s+   $
                        |    +- End of Line (2)
                        +- At least one whitespace (1)

            Rationale:
            Matches trailing whitespace (2) in lines containing at least one (1) non-whitespace character
        -->
        <property name="format" value="\s+$"/>
        <property name="message" value="Line containing trailing whitespace character(s)"/>
    </module>

    <!-- <module name="RegexpSingleline"> -->
    <!--   <property name="format" value="fqdn"/> -->
    <!-- </module> -->

    <!-- Space after // -->
    <module name="RegexpSingleline">
        <property name="format" value="^\s*//[^\s]"/>
        <property name="message" value="Comment start ('//') followed by non-space character. You would not continue after a punctuation without a space, would you?"/>
    </module>

    <module name="JavadocPackage">
    </module>

    <module name="TreeWalker">
        <module name="SuppressionCommentFilter"/>
        <module name="FinalClass"/>
        <module name="UnusedImports">
            <property name="processJavadoc" value="true"/>
        </module>
        <module name="AvoidStarImport"/>
        <module name="IllegalImport"/>
        <module name="RedundantImport"/>
        <module name="RedundantModifier"/>
        <module name="ModifierOrder"/>
        <module name="UpperEll"/>
        <module name="ArrayTypeStyle"/>
        <module name="GenericWhitespace"/>
        <module name="EmptyStatement"/>
        <module name="PackageDeclaration"/>
        <module name="LeftCurly"/>

        <!-- Spaces instead of Tabs -->
        <module name="RegexpSinglelineJava">
            <property name="format" value="^\t+"/>
            <property name="message" value="Indent must not use tab characters. Use space instead."/>
        </module>

        <module name="JavadocMethod">
            <!-- TODO stricten those checks -->
            <property name="scope" value="public"/>
            <!--<property name="allowUndeclaredRTE" value="true"/>-->
            <property name="allowMissingParamTags" value="true"/>
            <property name="allowMissingThrowsTags" value="true"/>
            <property name="allowMissingReturnTag" value="true"/>
            <property name="allowMissingJavadoc" value="true"/>
            <property name="suppressLoadErrors" value="true"/>
        </module>

        <module name="JavadocStyle">
            <property name="scope" value="public"/>
            <property name="checkEmptyJavadoc" value="true"/>
            <property name="checkHtml" value="false"/>
        </module>

        <module name="ParenPad">
        </module>

        <!-- Whitespace after key tokens -->
        <module name="NoWhitespaceAfter">
            <property name="tokens" value="INC
										 , DEC
										 , UNARY_MINUS
										 , UNARY_PLUS
										 , BNOT, LNOT
										 , DOT
										 , ARRAY_DECLARATOR
										 , INDEX_OP
										 "/>
        </module>

        <!-- Whitespace after key words -->
        <module name="WhitespaceAfter">
            <property name="tokens" value="TYPECAST
										 , LITERAL_IF
										 , LITERAL_ELSE
										 , LITERAL_WHILE
										 , LITERAL_DO
										 , LITERAL_FOR
										 , DO_WHILE
										 "/>
        </module>

        <module name="WhitespaceAround">
            <property
                    name="ignoreEnhancedForColon"
                    value="false"
            />
            <!-- Currently disabled tokens: LCURLY, RCURLY, WILDCARD_TYPE, GENERIC_START, GENERIC_END -->
            <property
                    name="tokens"
                    value="ASSIGN
					 , ARRAY_INIT
					 , BAND
					 , BAND_ASSIGN
					 , BOR
					 , BOR_ASSIGN
					 , BSR
					 , BSR_ASSIGN
					 , BXOR
					 , BXOR_ASSIGN
					 , COLON
					 , DIV
					 , DIV_ASSIGN
					 , DO_WHILE
					 , EQUAL
					 , GE
					 , GT
					 , LAMBDA
					 , LAND
					 , 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
					 , MINUS_ASSIGN
					 , MOD
					 , MOD_ASSIGN
					 , NOT_EQUAL
					 , PLUS
					 , PLUS_ASSIGN
					 , QUESTION
					 , SL
					 , SLIST
					 , SL_ASSIGN
					 , SR
					 , SR_ASSIGN
					 , STAR
					 , STAR_ASSIGN
					 , LITERAL_ASSERT
					 , TYPE_EXTENSION_AND
					 "/>
        </module>

        <!--
        <module name="CustomImportOrder">
            <property name="customImportOrderRules"
                      value="STATIC###STANDARD_JAVA_PACKAGE###SPECIAL_IMPORTS###THIRD_PARTY_PACKAGE"/>
            <property name="specialImportsRegExp" value="^org\.org.pgpainless.core\.org.pgpainless.core"/>
            <property name="sortImportsInGroupAlphabetically" value="true"/>
            <property name="separateLineBetweenGroups" value="true"/>
        </module>
        -->
    </module>
</module>