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="Trailing spaces are not allowed."/>
    </module>
    <module name="TreeWalker">
        <module name="ImportOrder">
            <property name="separatedStaticGroups" value="true" />
            <property name="option" value="bottom" />
        </module>
        <module name="UnusedImports" />
        <module name="AvoidStarImport" />
    </module>
</module>