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">
    <module name="FileTabCharacter"/>
    <module name="NewlineAtEndOfFile"/>

    <module name="RegexpSingleline">
        <property name="format" value="\s+$"/>
        <property name="message" value="Line has trailing whitespace."/>
    </module>

    <module name="TreeWalker">
        <module name="TodoComment"/>
        <module name="GenericWhitespace"/>

        <module name="Indentation">
            <property name="basicOffset" value="4"/>
            <property name="braceAdjustment" value="0"/>
            <property name="caseIndent" value="4"/>
            <property name="tabWidth" value="4"/>
            <property name="forceStrictCondition" value="true"/>
        </module>

        <!-- Variable names must be camelCase -->
        <module name="LocalVariableName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
        </module>
        <module name="MemberName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
        </module>
        <module name="ParameterName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
        </module>

        <!-- Class names must be PascalCase -->
        <module name="TypeName">
            <property name="format" value="^[A-Z][a-zA-Z0-9]*$"/>
        </module>
    </module>
</module>