checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC
        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
        "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">

    <!-- Ignore module-info.java files when compiling with JDK 11+ -->
    <module name="BeforeExecutionExclusionFileFilter">
        <property name="fileNamePattern" value="module\-info\.java$"/>
    </module>

    <!-- Checks that there are no tab characters ('\t') in the source code. -->
    <module name="FileTabCharacter">
        <property name="eachLine" value="true"/>
        <property name="fileExtensions" value="java,css,js,xml,jsp"/>
    </module>

    <!-- Checks for long lines. -->
    <module name="LineLength">
        <property name="max" value="120"/>
        <property name="fileExtensions" value="java"/>
    </module>

    <module name="TreeWalker">

        <!-- Check for invalid whitespace before commas, semicolons, etc -->
        <module name="NoWhitespaceBefore" />

        <!-- Check for empty statements -->
        <module name="EmptyStatement"/>

        <!-- Check that any module that implements equals or hashCode also implements the other -->
        <module name="EqualsHashCode"/>

        <!-- Checks for redundant import statements -->
        <module name="RedundantImport"/>

        <!-- Checks for unused import statements -->
        <module name="UnusedImports"/>

        <module name="RedundantModifier">
            <!-- Checks for redundant modifiers on various symbol definitions.
                See: http://checkstyle.sourceforge.net/config_modifier.html#RedundantModifier
            -->
            <property name="tokens" value="METHOD_DEF, VARIABLE_DEF, ANNOTATION_FIELD_DEF, INTERFACE_DEF, CLASS_DEF, ENUM_DEF"/>
        </module>

        <module name="ImportOrder">
            <property name="severity" value="error"/>
            <property name="groups" value="*,jakarta,javax,java"/>
            <property name="option" value="bottom"/>
            <property name="sortStaticImportsAlphabetically" value="true"/>
            <property name="tokens" value="IMPORT, STATIC_IMPORT"/>
            <property name="separated" value="true"/>
        </module>

        <module name="ModifierOrder">
            <!-- Warn if modifier order is inconsistent with JLS3 8.1.1, 8.3.1, and
                     8.4.3.  The prescribed order is:
                     public, protected, private, abstract, static, final, transient, volatile,
                     synchronized, native, strictfp
                -->
            <property name="severity" value="error"/>
        </module>

        <!-- Block import statements that use the * notation. -->
        <!-- <module name="AvoidStarImport">
          <property name="excludes" value="jakarta.ws.rs,jakarta.ws.rs.core,org.junit.jupiter.api.Assertions,org.mockito.Mockito,org.mockito.ArgumentMatchers"/>
        </module> -->

        <!-- Javadoc Checks -->
        <module name="JavadocParagraph"/>

        <module name="JavadocType">
            <property name="severity" value="error"/>
            <property name="scope" value="public"/>
            <property name="excludeScope" value="anoninner"/>
            <property name="allowMissingParamTags" value="false"/>
        </module>

        <module name="JavadocMethod">
            <property name="accessModifiers" value="public"/>
        </module>

        <module name="JavadocStyle">
            <property name="severity" value="error"/>
            <property name="checkHtml" value="true"/>
        </module>

        <module name="MethodName">
            <property name="severity" value="error"/>
        </module>

        <module name="ParameterName">
            <property name="severity" value="error"/>
        </module>

        <module name="LocalVariableName">
            <property name="severity" value="error"/>
        </module>

        <module name="LocalFinalVariableName">
            <!-- Validates identifiers for local final variables against the
            expression "^[a-z][a-zA-Z0-9]*$". -->
            <property name="severity" value="error"/>
        </module>

        <!-- Type parameters must be either one of the four blessed letters
        T, U, K, V, W, X or else be capital-case terminated with a T,
        such as MyGenericParameterT -->
        <module name="ClassTypeParameterName">
            <property name="format" value="^(((T|U|K|V|W|X|R)[0-9]*)|([A-Z][a-z][a-zA-Z]*))$"/>
            <property name="severity" value="error"/>
        </module>

        <module name="MethodTypeParameterName">
            <property name="format" value="^(((T|U|K|V|W|X|R)[0-9]*)|([A-Z][a-z][a-zA-Z]*T))$"/>
            <property name="severity" value="error"/>
        </module>

        <module name="InterfaceTypeParameterName">
            <property name="format" value="^(((T|U|K|V|W|X|R)[0-9]*)|([A-Z][a-z][a-zA-Z]*T))$"/>
            <property name="severity" value="error"/>
        </module>

        <!-- K&R style braces -->
        <!-- <module name="NeedBraces"/> -->
        <module name="LeftCurly"/>
        <module name="RightCurly"/>
        <module name="WhitespaceAround">
            <property name="tokens"
                      value="ASSIGN, BAND, BAND_ASSIGN, BOR, BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN, EQUAL, GE, GT, LAND, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF, LITERAL_RETURN, 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, TYPE_EXTENSION_AND"
            />
        </module>
        <module name="Indentation">
            <property name="throwsIndent" value="8"/>
        </module>
        <module name="SuppressWarningsHolder"/>
        <module name="FinalClass"/>
        <module name="FinalLocalVariable"/>
        <module name="FinalParameters"/>
        <module name="GenericWhitespace"/>
        <module name="HideUtilityClassConstructor"/>
        <module name="MultipleStringLiterals">
            <property name="allowedDuplicates" value="4"/>
            <property name="ignoreStringsRegexp" value='^(?:("\\"")|(",")|("=")|(""))$'/>
        </module>
        <module name="MultipleVariableDeclarations"/>
    </module>

    <!-- No Trailing Whitespace, except on lines that only have an asterisk (e.g. Javadoc comments) -->
    <module name="RegexpSingleline">
        <property name="format" value="(?&lt;!\*)\s+$|\*\s\s+$"/>
        <property name="message" value="Trailing whitespace"/>
        <property name="fileExtensions" value="java,css,js,xml"/>
    </module>
    <module name="SuppressWarningsFilter" />

    <module name="SuppressionFilter">
        <property name="file" value="checkstyle-suppressions.xml"/>
        <property name="optional" value="false"/>
    </module>
</module>