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">
    <!--
        This Checker module contains the configuration for the Checkstyle tool.
        It defines the checks that will be performed on the Java source code.
        The configuration is based on the Google Java Style Guide, with modifications
        to match the existing code style of the Railroad project.
    -->


    <!-- Checks for Size Violations. -->
    <!-- See https://checkstyle.sourceforge.io/config_sizes.html -->
    <module name="FileLength"/>
    <module name="LineLength">
        <property name="max" value="120"/>
        <property name="ignorePattern" value="^package .*|^import .*|a href|href"/>
    </module>

    <!-- Checks for whitespace. -->
    <!-- See https://checkstyle.sourceforge.io/config_whitespace.html -->
    <module name="FileTabCharacter"/>

    <!-- Miscellaneous checks. -->
    <!-- See https://checkstyle.sourceforge.io/config_misc.html -->

    <module name="Translation"/>

    <module name="TreeWalker">
        <!--
            The TreeWalker module processes the Java source code as an abstract syntax tree (AST).
            It contains checks that are applied to individual Java files.
        -->

        <!-- Checks for Naming Conventions. -->
        <!-- See https://checkstyle.sourceforge.io/config_naming.html -->
        <module name="PackageName">
            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
        </module>
        <module name="TypeName">
            <property name="format" value="^[A-Z][a-zA-Z0-9]*$"/>
        </module>
        <module name="MethodName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
        </module>
        <module name="ParameterName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
        </module>
        <module name="LocalVariableName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
        </module>
        <module name="ConstantName">
            <property name="format" value="^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$"/>
        </module>

        <!-- Checks for Javadoc comments. -->
        <!-- See https://checkstyle.sourceforge.io/config_javadoc.html -->
        <module name="JavadocMethod"/>
        <module name="JavadocType"/>

        <!-- Checks for Imports. -->
        <!-- See https://checkstyle.sourceforge.io/config_imports.html -->

        <module name="UnusedImports"/>
        <module name="RedundantImport"/>
        <module name="IllegalImport"/> <!-- disallow sun.* packages -->


        <!-- Checks for Whitespace. -->
        <!-- See https://checkstyle.sourceforge.io/config_whitespace.html -->
        <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,LCURLY,LE,LITERAL_ASSERT,LITERAL_CATCH,LITERAL_DO,LITERAL_ELSE,LITERAL_FINALLY,LITERAL_FOR,LITERAL_IF,LITERAL_RETURN,LITERAL_SYNCHRONIZED,LITERAL_TRY,LITERAL_WHILE,LT,MINUS,MINUS_ASSIGN,MOD,MOD_ASSIGN,NOT_EQUAL,PLUS,PLUS_ASSIGN,QUESTION,RCURLY,SL,SL_ASSIGN,SR,SR_ASSIGN,STAR,STAR_ASSIGN,TYPE_EXTENSION_AND,WILDCARD_TYPE"/>
        </module>
        <module name="NoWhitespaceBefore"/>
        <module name="NoWhitespaceAfter"/>
        <module name="ParenPad"/>
        <module name="MethodParamPad"/>
        <module name="NoLineWrap"/>
        <module name="EmptyForInitializerPad"/>
        <module name="EmptyForIteratorPad"/>
        <module name="GenericWhitespace"/>
        <module name="WhitespaceAfter"/>
        <module name="NoWhitespaceBeforeCaseDefaultColon"/>

        <!-- Checks for Modifiers. -->
        <!-- See https://checkstyle.sourceforge.io/config_modifiers.html -->
        <module name="ModifierOrder"/>
        <module name="RedundantModifier"/>

        <!-- Checks for Blocks. -->
        <!-- See https://checkstyle.sourceforge.io/config_blocks.html -->
        <module name="EmptyBlock">
            <property name="option" value="TEXT"/>
            <property name="tokens"
                      value="LITERAL_CATCH,LITERAL_FINALLY,LITERAL_IF,LITERAL_FOR,LITERAL_WHILE,STATIC_INIT"/>
        </module>

        <module name="LeftCurly">
            <property name="option" value="EOL"/> <!-- K&R style -->
        </module>
        <module name="RightCurly">
            <property name="option" value="SAME"/>
        </module>

        <!-- Checks for Coding Problems. -->
        <!-- See https://checkstyle.sourceforge.io/config_coding.html -->
        <module name="EqualsHashCode"/>
        <module name="InnerAssignment"/>
        <module name="MissingSwitchDefault"/>
        <module name="FallThrough"/>
        <module name="MultipleVariableDeclarations"/>
        <module name="SimplifyBooleanExpression"/>
        <module name="SimplifyBooleanReturn"/>
        <module name="StringLiteralEquality"/>
        <module name="SuperFinalize"/>
        <module name="UnnecessaryParentheses"/>
        <module name="OneStatementPerLine"/>
        <module name="OverloadMethodsDeclarationOrder"/>
        <module name="ReturnCount">
            <property name="max" value="2"/>
        </module>
        <module name="DefaultComesLast"/>
        <module name="EmptyStatement"/>
        <module name="IllegalInstantiation"/>
        <module name="IllegalTokenText"/>
        <module name="IllegalType"/>
        <module name="MissingOverride"/>
        <module name="NoArrayTrailingComma"/>
        <module name="NoEnumTrailingComma"/>
        <module name="NoFinalizer"/>

        <module name="NoWhitespaceAfter"/>
        <module name="NoWhitespaceBefore"/>
        <module name="OperatorWrap"/>
        <module name="OuterTypeFilename"/>
        <module name="PackageAnnotation"/>
        <module name="ParameterAssignment"/>

        <module name="RequireThis"/>
        <module name="ThrowsCount"/>
        <module name="UnnecessarySemicolonInTryWithResources"/>
        <module name="VariableDeclarationUsageDistance"/>
        <module name="ArrayTypeStyle"/>
        <module name="MissingDeprecated"/>
        <module name="MissingOverride"/>
        <module name="PackageDeclaration"/>
        <module name="UnnecessaryParentheses"/>
        <module name="VisibilityModifier"/>

        <!-- Checks for Class Design. -->
        <!-- See https://checkstyle.sourceforge.io/config_design.html -->
        <module name="FinalClass"/>
        <module name="HideUtilityClassConstructor"/>
        <module name="InterfaceIsType"/>
        <module name="MutableException"/>
        <module name="ThrowsCount"/>
        <module name="VisibilityModifier"/>

        <!-- Metrics. -->
        <!-- See https://checkstyle.sourceforge.io/config_metrics.html -->
        <module name="CyclomaticComplexity">
            <property name="max" value="20"/>
        </module>
        <module name="JavaNCSS"/>
        <module name="NPathComplexity"/>
    </module>
</module>