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">
    <property name="severity" value="error" />

    <property name="fileExtensions" value="java, properties, xml" />

    <module name="TreeWalker">
        <module name="EmptyBlock" />
        <module name="RegexpSinglelineJava">
            <property name="format" value="^\t* " />
            <property name="message" value="Indent must use tab characters" />
            <property name="ignoreComments" value="true" />
        </module>

        <!-- Checks for Javadoc comments.                     -->
        <!-- See https://checkstyle.org/config_javadoc.html -->
        <module name="InvalidJavadocPosition" />
        <module name="JavadocMethod">
            <property name="allowedAnnotations" value="Override, Bean" />
            <property name="tokens" value="METHOD_DEF" />
        </module>
        <module name="JavadocType">
            <property name="scope" value="protected" />
        </module>

        <!-- Checks for Naming Conventions.                  -->
        <!-- See https://checkstyle.org/config_naming.html -->
        <module name="PackageName" />

        <!-- Checks for imports                              -->
        <!-- See https://checkstyle.org/config_imports.html -->
        <module name="IllegalImport" /> <!-- defaults to sun.* packages -->
        <module name="RedundantImport" />
        <module name="UnusedImports">
            <property name="processJavadoc" value="true" />
        </module>

        <!-- Checks for whitespace                               -->
        <!-- See https://checkstyle.org/config_whitespace.html -->
        <module name="EmptyForIteratorPad" />
        <module name="GenericWhitespace" />
        <module name="MethodParamPad" />
        <module name="NoWhitespaceBefore" />
        <module name="TypecastParenPad" />
        <module name="WhitespaceAfter" />

        <!-- Modifier Checks                                    -->
        <!-- See https://checkstyle.org/config_modifier.html -->
        <module name="ModifierOrder" />

        <!-- Checks for blocks. You know, those {}'s         -->
        <!-- See https://checkstyle.org/config_blocks.html -->
        <module name="AvoidNestedBlocks" />
        <module name="EmptyBlock" />

        <!-- Checks for common coding problems               -->
        <!-- See https://checkstyle.org/config_coding.html -->
        <module name="EmptyStatement" />
        <module name="IllegalInstantiation" />
        <module name="InnerAssignment" />
        <module name="SimplifyBooleanExpression" />
        <module name="SimplifyBooleanReturn" />

        <!-- Checks for class design                         -->
        <!-- See https://checkstyle.org/config_design.html -->
        <module name="FinalClass" />
        <module name="InterfaceIsType" />

        <!-- Miscellaneous other checks.                   -->
        <!-- See https://checkstyle.org/config_misc.html -->
        <module name="ArrayTypeStyle" />
        <module name="TodoComment" />
        <module name="UpperEll" />

        <!-- https://checkstyle.org/config_filters.html#SuppressionXpathFilter -->
        <module name="SuppressionXpathFilter">
            <property name="file" value="${org.checkstyle.sun.suppressionxpathfilter.config}"
                default="checkstyle-xpath-suppressions.xml" />
            <property name="optional" value="true" />
        </module>
    </module>
</module>