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">
    <module name="FileTabCharacter">
        <property name="eachLine" value="true"/>
    </module>
    <module name="LineLength">
        <property name="max" value="120"/>
    </module>
    <!-- Coding style rules -->
    <module name="TreeWalker">

        <!-- Naming conventions -->
        <module name="ConstantName"/>
        <module name="LocalVariableName"/>
        <module name="MemberName"/>
        <module name="MethodName"/>
        <module name="PackageName"/>
        <module name="ParameterName"/>
        <module name="TypeName"/>

        <!-- Imports -->
        <module name="UnusedImports"/>

        <!-- Formatting -->
        <module name="WhitespaceAround"/>
        <module name="WhitespaceAfter"/>
        <module name="Indentation"/>
        <module name="LeftCurly"/>
        <module name="RightCurly"/>

        <!-- Miscellaneous -->
        <module name="VisibilityModifier">
            <property name="protectedAllowed" value="true"/>
        </module>
        <module name="NestedIfDepth">
            <property name="max" value="3"/>
        </module>
        <module name="JavadocMethod">
            <property name="accessModifiers" value="public,protected"/>
        </module>
        <module name="JavadocStyle">
            <property name="checkEmptyJavadoc" value="true" />
            <property name="scope" value="protected" />
        </module>
        <module name="JavadocType">
            <property name="allowMissingParamTags" value="true" />
            <property name="scope" value="protected" />
        </module>
    </module>
</module>