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>

    <!-- Checks whether files end with a new line.                        -->
    <!-- See https://checkstyle.org/config_misc.html#NewlineAtEndOfFile -->
    <module name="NewlineAtEndOfFile"/>

    <!-- Checks for white space at the end of the line -->
    <!-- See http://checkstyle.sourceforge.net/config_regexp.html -->
    <!-- Updated to ignore whitespace following '*' in javadoc comments -->
    <!-- http://stackoverflow.com/questions/9100059/checkstyle-trailing-spaces-regexp-issue -->
    <module name="RegexpSingleline">
        <property name="format" value="(?&lt;!\A[ \t]*\*?)[ \t]$"/>
        <property name="message" value="Line has trailing spaces."/>
        <property name="fileExtensions" value="java"/>
    </module>

    <module name="TreeWalker">
        <!--
           Exceptions
           See https://checkstyle.sourceforge.io/config_filters.html
         -->
        <module name="SuppressionCommentFilter" />
        <module name="SuppressWithNearbyCommentFilter"/>

        <!-- Checks for Javadoc comments.                   -->
        <!-- See https://checkstyle.org/config_javadoc.html -->
        <module name="InvalidJavadocPosition"/>

        <!-- Checks for imports                             -->
        <!-- See https://checkstyle.org/config_imports.html -->
        <module name="AvoidStarImport"/>
        <module name="IllegalImport"/> <!-- defaults to sun.* packages -->
        <module name="RedundantImport"/>
        <module name="UnusedImports"/>
        <module name="ImportOrder">
            <property name="groups" value="java,javax,net.logstash"/>
            <property name="ordered" value="true"/>
            <property name="separated" value="true"/>
            <property name="option" value="top"/>
            <property name="sortStaticImportsAlphabetically" value="true"/>
        </module>
        
        <!-- Checks for whitespace                             -->
        <!-- See https://checkstyle.org/config_whitespace.html -->
        <module name="EmptyForIteratorPad"/>
        <module name="GenericWhitespace"/>
        <module name="MethodParamPad"/>
        <module name="NoWhitespaceAfter"/>
        <module name="NoWhitespaceBefore"/>
        <module name="OperatorWrap"/>
        <module name="ParenPad"/>
        <module name="TypecastParenPad"/>
        <module name="WhitespaceAfter"/>
        <module name="WhitespaceAround"/>

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

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

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

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

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