checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC
    "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
    "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<module name="Checker">
    <property name="localeLanguage" value="en"/>

    <module name="FileTabCharacter">
        <property name="fileExtensions" value="java"/>
    </module>

    <module name="TreeWalker">

        <!-- code cleanup -->
        <module name="UnusedImports">
            <property name="processJavadoc" value="true"/>
        </module>
        <module name="RedundantImport"/>
        <module name="IllegalImport"/>
        <module name="EqualsHashCode"/>
        <module name="SimplifyBooleanExpression"/>
        <module name="OneStatementPerLine"/>
        <module name="UnnecessaryParentheses"/>
        <module name="SimplifyBooleanReturn"/>

        <!-- style -->
        <module name="DefaultComesLast"/>
        <module name="EmptyStatement"/>
        <module name="ArrayTypeStyle"/>
        <module name="UpperEll"/>
        <module name="LeftCurly"/>
        <module name="RightCurly"/>
        <module name="EmptyStatement"/>
        <module name="ConstantName">
            <property name="format" value="(^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$)|(^log$)"/>
        </module>
        <module name="LocalVariableName"/>
        <module name="LocalFinalVariableName"/>
        <module name="MemberName"/>
        <module name="ClassTypeParameterName">
            <property name="format" value="^[A-Z0-9]*$"/>
        </module>
        <module name="MethodTypeParameterName">
            <property name="format" value="^[A-Z0-9]*$"/>
        </module>
        <module name="PackageName"/>
        <module name="ParameterName"/>
        <module name="StaticVariableName"/>
        <module name="TypeName"/>
        <module name="AvoidStarImport"/>


        <!-- whitespace -->
        <module name="GenericWhitespace"/>
        <module name="NoWhitespaceBefore"/>
        <module name="WhitespaceAfter"/>
        <module name="NoWhitespaceAfter"/>
        <module name="WhitespaceAround">
            <property name="allowEmptyConstructors" value="true"/>
            <property name="allowEmptyMethods" value="true"/>
        </module>
        <module name="Indentation"/>
        <module name="MethodParamPad"/>
        <module name="ParenPad"/>
        <module name="TypecastParenPad"/>

        <!-- locale-sensitive methods should specify locale -->
        <module name="Regexp">
            <property name="format" value="\.to(Lower|Upper)Case\(\)"/>
            <property name="illegalPattern" value="true"/>
            <property name="ignoreComments" value="true"/>
        </module>
    </module>
</module>