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">
<!-- This is a checkstyle configuration file.
  -
  - Checkstyle configuration: http://checkstyle.sourceforge.net/config.html
  - List of standard checks: https://checkstyle.sourceforge.io/checks.html
  -->
<module name="Checker">

    <!-- Checks that there are no tab characters in the file. -->
    <module name="FileTabCharacter">
        <property name="eachLine" value="true" />
    </module>

    <!-- Checks whether files end with a line separator. -->
    <module name="NewlineAtEndOfFile" />

    <!-- Checks that a specified pattern matches a single line in any file type. -->
    <module name="RegexpSingleline">
        <!-- \s matches whitespace character, $ matches end of line. -->
        <property name="format" value="\s+$" />
        <property name="message" value="Line has trailing spaces." />
    </module>

    <module name="FileLength">
        <property name="max" value="2000" />
    </module>

    <!-- All Java AST specific tests live under TreeWalker module. -->
    <module name="TreeWalker">

        <!-- ==== IMPORT CHECKS ==== -->

        <!-- Checks that there are no import statements that use the * notation. -->
        <module name="AvoidStarImport">
            <property name="allowStaticMemberImports" value="true" />
        </module>

        <!-- Checks for redundant import statements. -->
        <module name="RedundantImport" />

        <!-- Checks for unused import statements. -->
        <module name="UnusedImports">
            <property name="processJavadoc" value="true" />
        </module>

        <!-- Checks for imports from a set of illegal packages. -->
        <module name="IllegalImport">
            <property name="illegalPkgs" value="junit.framework" />
        </module>

        <!-- ==== NAMING CHECKS ==== -->

        <module name="PackageName" />

        <module name="TypeName" />

        <module name="ConstantName" />

        <module name="StaticVariableName" />

        <module name="MemberName" />

        <module name="MethodName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*(_[a-zA-Z0-9]+)*$" />
        </module>

        <module name="ParameterName" />

        <module name="LocalFinalVariableName" />

        <module name="LocalVariableName" />

        <!-- ==== CODING CHECKS ==== -->

        <!-- Checks for the placement of left curly braces ('{') for code blocks. -->
        <module name="LeftCurly">
            <!-- The brace must always be on the end of the line. -->
            <property name="option" value="eol" />
        </module>

        <!-- Checks the placement of right curly braces ('}') for code blocks. -->
        <module name="RightCurly">
            <!-- brace should be on the same line as the next part of a multi-block statement. -->
            <property name="option" value="same" />
        </module>

        <module name="EmptyLineSeparator">
            <property name="allowNoEmptyLineBetweenFields" value="true"/>
        </module>

        <module name="EmptyBlock" />

        <module name="EmptyCatchBlock" />

        <!-- Checks for braces around code blocks. -->
        <module name="NeedBraces" />

        <!-- Checks that long constants are defined with an upper ell. -->
        <module name="UpperEll" />

        <!-- Checks for fall-through in switch statements. -->
        <module name="FallThrough" />

        <!-- ==== MODIFIERS CHECKS ==== -->

        <!-- Checks that the order of modifiers conforms to the suggestions in the Java Language specification -->
        <module name="ModifierOrder" />

        <!-- Checks for redundant modifiers. -->
        <module name="RedundantModifier" />

        <!-- ==== WHITESPACE CHECKS ==== -->

        <!-- Checks that a token is surrounded by whitespace. -->
        <module name="WhitespaceAround" />

        <!-- Checks that a token is followed by whitespace -->
        <module name="WhitespaceAfter" />

        <!-- Checks that there is no whitespace before a token. -->
        <module name="NoWhitespaceBefore" />

        <!-- Checks the policy on the padding of parentheses. -->
        <module name="ParenPad" />

        <!-- Checks correct indentation of Java code. -->
        <module name="Indentation">
            <property name="basicOffset" value="4" />
            <property name="braceAdjustment" value="0" />
            <property name="caseIndent" value="4" />
            <property name="throwsIndent" value="4" />
            <property name="lineWrappingIndentation" value="4" />
            <property name="arrayInitIndent" value="8" />
        </module>

        <!-- ==== DESIGN CHECKS ==== -->

        <module name="MissingOverride" />

        <module name="MutableException" />

        <module name="MethodLength">
            <property name="max" value="150" />
        </module>

        <module name="ParameterNumber">
            <property name="max" value="9" />
            <property name="tokens" value="METHOD_DEF" />
        </module>

        <module name="CyclomaticComplexity">
            <property name="max" value="15" />
        </module>

    </module>
</module>