etc/checkstyle.xml

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

    Copyright (c) 2019, 2024 Oracle and/or its affiliates. All rights reserved.

    This program and the accompanying materials are made available under the
    terms of the Eclipse Public License v. 2.0 which is available at
    http://www.eclipse.org/legal/epl-2.0,
    or the Eclipse Distribution License v. 1.0 which is available at
    http://www.eclipse.org/org/documents/edl-v10.php.

    SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause

-->

<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN" "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<!--
    This file is based on maven-checkstyle-plugin config/sun_checks.xml file.
    Checkstyle configuration that checks the coding conventions based on:
      - the Java Language Specification at
        http://java.sun.com/docs/books/jls/second_edition/html/index.html
      - the Sun Code Conventions at http://java.sun.com/docs/codeconv/
      - the Javadoc guidelines at
        http://java.sun.com/j2se/javadoc/writingdoccomments/index.html
      - the JDK Api documentation http://java.sun.com/j2se/docs/api/index.html
      - some custom relaxations of the rules above & best practices
    Checkstyle is very configurable. Be sure to read the documentation at
    http://checkstyle.sf.net (or in your downloaded distribution).
    Most Checks are configurable, be sure to consult the documentation.
    To completely disable a check, just comment it out or delete it from the file.
    Finally, it is worth reading the documentation.
-->

<module name="Checker">

    <!-- exclude module-info.java check - checkstyle can't process it -->
    <module name="BeforeExecutionExclusionFileFilter">
        <property name="fileNamePattern" value="module\-info\.java$"/>
    </module>

    <!--
        If you set the basedir property below, then all reported file
        names will be relative to the specified directory. See
        http://checkstyle.sourceforge.net/5.x/config.html#Checker
        <property name="basedir" value="${basedir}"/>
    -->
    <property name="charset" value="UTF-8"/>

    <!-- Checks that each Java package has a Javadoc file used for commenting. -->
    <!-- See http://checkstyle.sf.net/config_javadoc.html#JavadocPackage       -->
<!--    <module name="JavadocPackage" />-->

    <!-- Checks to see if a file contains a tab character. -->
    <module name="FileTabCharacter">
        <property name="eachLine" value="true"/>
    </module>

    <!--
     Making sure we do not have @author tags in javadocs
     There is a list of developers in pom.xml that is sufficient for our needs.
     See https://github.com/checkstyle/checkstyle/issues/5339
    -->
    <module name="RegexpSingleline">
        <!-- The '.' in id is needed, otherwise ArrayIndexOutOfBounds happens -->
        <property name="id" value="Javadoc.javadocNoAuthor"/>
        <property name="format" value="^\s*\*\s*@author"/>
        <property name="minimum" value="0"/>
        <property name="maximum" value="0"/>
        <property name="message" value="Javadoc has illegal ''author'' tag."/>
        <property name="fileExtensions" value="java"/>
    </module>

    <!-- Checks that property files contain the same keys.         -->
    <!-- See http://checkstyle.sf.net/config_misc.html#Translation -->
    <module name="Translation"/>

    <module name="FileLength"/>

    <module name="SuppressWarningsFilter"/>
    <module name="TreeWalker">
        <module name="SuppressionCommentFilter">
            <property name="offCommentFormat" value="CHECKSTYLE.OFF\: ([\w\|]+)"/>
            <property name="onCommentFormat" value="CHECKSTYLE.ON\: ([\w\|]+)"/>
            <property name="checkFormat" value="$1"/>
        </module>
        <module name="SuppressWarningsHolder"/>

        <!-- Checks for Javadoc comments.                     -->
        <!-- See http://checkstyle.sf.net/config_javadoc.html -->
        <module name="JavadocMethod">
            <property name="accessModifiers" value="protected"/>
            <property name="allowMissingReturnTag" value="true"/>
            <property name="allowMissingParamTags" value="true"/>
        </module>
        <module name="JavadocType">
            <property name="scope" value="protected"/>
        </module>
        <module name="JavadocVariable">
            <property name="scope" value="protected"/>
        </module>
        <module name="JavadocStyle"/>

        <!-- Checks for Naming Conventions.                  -->
        <!-- See http://checkstyle.sf.net/config_naming.html -->
        <module name="ConstantName"/>
        <module name="LocalFinalVariableName"/>
        <module name="LocalVariableName"/>
        <module name="MemberName"/>
        <module name="MethodName"/>
        <module name="PackageName"/>
        <module name="ParameterName"/>
        <module name="StaticVariableName"/>
        <module name="TypeName"/>

        <!-- Checks for imports                              -->
        <!-- See http://checkstyle.sf.net/config_import.html -->
        <module name="AvoidStarImport"/>
        <module name="UnusedImports"/>
        <module name="IllegalImport"/> <!-- defaults to sun.* packages -->
        <module name="RedundantImport"/>
        <module name="ImportOrder">
            <property name="groups" value="java, javax, jakarta, org.eclipse.yasson"/>
            <property name="ordered" value="true"/>
            <property name="separated" value="true"/>
            <property name="option" value="bottom"/>
        </module>

        <!-- Checks for blocks. You know, those {}'s         -->
        <!-- See http://checkstyle.sf.net/config_blocks.html -->
        <module name="AvoidNestedBlocks"/>
        <module name="EmptyBlock">
            <property name="option" value="TEXT"/>
            <property name="tokens" value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH"/>
        </module>
        <module name="NeedBraces">
            <property name="allowSingleLineStatement" value="true"/>
        </module>
        <module name="LeftCurly"/>
        <module name="RightCurly"/>
        <module name="RightCurly">
            <property name="option" value="alone"/>
            <property name="tokens"
                    value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, STATIC_INIT, INSTANCE_INIT"/>
        </module>

        <!-- Indentation -->
        <property name="tabWidth" value="4"/>

        <!-- Wrapping Lines -->
        <module name="NoLineWrap"/>
        <module name="SeparatorWrap">
            <property name="tokens" value="DOT"/>
            <property name="option" value="nl"/>
        </module>
        <module name="SeparatorWrap">
            <property name="tokens" value="COMMA"/>
            <property name="option" value="EOL"/>
        </module>

        <!-- Several variable declaration on one line: int i, p; -->
        <module name="MultipleVariableDeclarations"/>

        <module name="OuterTypeFilename"/>
        <module name="OneTopLevelClass"/>

        <!-- Checks for whitespace                               -->
        <!-- See http://checkstyle.sf.net/config_whitespace.html -->
        <module name="OperatorWrap"/>
        <module name="WhitespaceAfter"/>
        <module name="MethodParamPad"/>
        <module name="NoWhitespaceAfter"/>
        <module name="NoWhitespaceBefore"/>
        <module name="ParenPad"/>
        <module name="TypecastParenPad"/>
        <module name="WhitespaceAfter"/>
        <module name="WhitespaceAround">
            <!-- Removed static initializer issues: RCURLY, SLIST -->
            <property name="tokens"
                    value="ASSIGN, BAND, BAND_ASSIGN, BOR, BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV,
                            DIV_ASSIGN, DO_WHILE, EQUAL, GE, GT, LAND, LCURLY, LE, LITERAL_ASSERT, 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, SL_ASSIGN, SR, SR_ASSIGN, STAR, STAR_ASSIGN,
                            TYPE_EXTENSION_AND"/>
            <property name="allowEmptyConstructors" value="true"/>
            <property name="allowEmptyMethods" value="true"/>
            <property name="allowEmptyTypes" value="true"/>
            <property name="allowEmptyLoops" value="true"/>
            <message key="ws.notFollowed"
                    value="WhitespaceAround: ''{0}'' is not followed by whitespace. Empty blocks may only be represented as '{}' when not part of a multi-block statement (4.1.3)"/>
            <message key="ws.notPreceded"
                    value="WhitespaceAround: ''{0}'' is not preceded with whitespace."/>
        </module>

        <module name="GenericWhitespace">
            <message key="ws.followed"
                    value="GenericWhitespace ''{0}'' is followed by whitespace."/>
            <message key="ws.preceded"
                    value="GenericWhitespace ''{0}'' is preceded with whitespace."/>
            <message key="ws.illegalFollow"
                    value="GenericWhitespace ''{0}'' should followed by whitespace."/>
            <message key="ws.notPreceded"
                    value="GenericWhitespace ''{0}'' is not preceded with whitespace."/>
        </module>

        <!-- Modifier Checks                                    -->
        <!-- See http://checkstyle.sf.net/config_modifiers.html -->
        <module name="ModifierOrder"/>
        <module name="RedundantModifier"/>

        <!-- Checks for common coding problems               -->
        <!-- See http://checkstyle.sf.net/config_coding.html -->
        <module name="EmptyStatement"/>
        <module name="EqualsHashCode"/>
        <module name="IllegalInstantiation"/>
        <module name="InnerAssignment"/>
        <module name="MissingSwitchDefault"/>

        <module name="SimplifyBooleanExpression"/>
        <module name="SimplifyBooleanReturn"/>

        <!-- Checks for class design                         -->
        <!-- See http://checkstyle.sf.net/config_design.html -->
        <module name="HideUtilityClassConstructor"/>
        <module name="InterfaceIsType"/>
        <module name="VisibilityModifier">
            <property name="packageAllowed" value="true"/>
        </module>
        <module name="ThrowsCount">
            <property name="max" value="3"/>
        </module>

        <!-- Miscellaneous other checks.                   -->
        <!-- See http://checkstyle.sf.net/config_misc.html -->
        <module name="ArrayTypeStyle"/>
        <module name="TodoComment"/>
        <module name="UpperEll"/>

        <module name="OneStatementPerLine"/>
<!--        <module name="FallThrough"/>-->

        <module name="NoFinalizer"/>
    </module>
</module>