checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
        "https://www.puppycrawl.com/dtds/configuration_1_3.dtd">

<!-- Full List of available checks: http://checkstyle.sourceforge.net/checks.html -->

<module name="Checker">
    <property name="charset" value="UTF-8"/>
    <property name="severity" value="warning"/>

    <!-- Files excluded from being processed -->
    <module name="BeforeExecutionExclusionFileFilter">
        <property name="fileNamePattern" value=".*archetype.*"/>
    </module>

    <module name="SuppressionFilter">
        <property name="file" value="${checkstyle.suppressions.file}"/>
        <property name="optional" value="false"/>
    </module>

    <module name="SuppressWarningsFilter"/>

    <module name="TreeWalker">
        <!-- Checkstyle only on files that end  with java -->
        <property name="fileExtensions" value="java"/>

        <!-- Allows annotations to be used for suppressing warnings -->
        <module name="SuppressWarningsHolder"/>

        <module name="SuppressionCommentFilter">
            <property name="checkFormat" value="indentation"/>
            <property name="messageFormat" value=".*method def.*"/>
        </module>

        <!-- Checks for redundant and unused imports -->
        <!-- http://checkstyle.sourceforge.net/config_imports.html#RefundantImport -->
        <!-- http://checkstyle.sourceforge.net/config_imports.html#UnusedImport -->
        <module name="RedundantImport"/>
        <module name="UnusedImports"/>

        <!-- Check for braces -->
        <!-- http://checkstyle.sourceforge.net/config_blocks.html#NeedBraces -->
        <module name="NeedBraces"/>

        <!-- Checks for correct indentation -->
        <!-- http://checkstyle.sourceforge.net/config_misc.html#Indentation -->
        <module name="Indentation">
            <property name="arrayInitIndent" value="8"/>
            <property name="caseIndent" value="4"/>
        </module>

        <!-- Checks that non-whitespace characters are separated by no more than one whitespace, including comments -->
        <!-- http://checkstyle.sourceforge.net/config_whitespace.html#SingleSpaceSeparator -->
        <module name="SingleSpaceSeparator">
            <property name="validateComments" value="true"/>
        </module>
    </module>
</module>