checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN" "https://checkstyle.org/dtds/configuration_1_3.dtd">

<!--

  Checkstyle configuration that checks the sun coding conventions from:

    - the Java Language Specification at
      https://docs.oracle.com/javase/specs/jls/se11/html/index.html

    - the Sun Code Conventions at
https://www.oracle.com/java/technologies/javase/codeconventions-contents.html

    - the Javadoc guidelines at
      https://www.oracle.com/technical-resources/articles/java/javadoc-tool.html

    - the JDK Api documentation https://docs.oracle.com/en/java/javase/11/

    - some best practices

  Checkstyle is very configurable. Be sure to read the documentation at
  https://checkstyle.org (or in your downloaded distribution).

  Most Checks are configurable, be sure to consult the documentation.

  To completely disable a check, just comment it out or delete it from the file.
  To suppress certain violations please review suppression filters.

  Finally, it is worth reading the documentation.

-->

<module name="Checker">
  <!--
      If you set the basedir property below, then all reported file
      names will be relative to the specified directory. See
      https://checkstyle.org/config.html#Checker

      <property name="basedir" value="${basedir}"/>
  -->
  <property name="severity" value="error" />

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

  <!-- Excludes all 'module-info.java' files              -->
  <!-- See https://checkstyle.org/filefilters/index.html -->
  <module name="BeforeExecutionExclusionFileFilter">
    <property name="fileNamePattern" value="module\-info\.java$" />
  </module>

  <!-- https://checkstyle.org/filters/suppressionfilter.html -->
  <module name="SuppressionFilter">
    <property name="file" value="${org.checkstyle.sun.suppressionfilter.config}"
      default="checkstyle-suppressions.xml" />
    <property name="optional" value="true" />
  </module>

  <!-- Checks that a package-info.java file exists for each package.     -->
  <!-- See https://checkstyle.org/checks/javadoc/javadocpackage.html#JavadocPackage -->
  <module name="JavadocPackage" />

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

  <!-- Checks that property files contain the same keys.         -->
  <!-- See https://checkstyle.org/checks/misc/translation.html -->
  <module name="Translation" />

  <!-- Checks for Size Violations.                    -->
  <!-- See https://checkstyle.org/checks/sizes/index.html -->
  <module name="FileLength" />
  <module name="LineLength">
    <property name="max" value="120" />
    <property name="fileExtensions" value="java" />
  </module>

  <!-- Checks for whitespace                               -->
  <!-- See https://checkstyle.org/checks/whitespace/index.html -->
  <module name="FileTabCharacter" />

  <!-- Miscellaneous other checks.                   -->
  <!-- See https://checkstyle.org/checks/misc/index.html -->
  <module name="RegexpSingleline">
    <property name="format" value="\s+$" />
    <property name="minimum" value="0" />
    <property name="maximum" value="0" />
    <property name="message" value="Line has trailing spaces." />
  </module>

  <!-- Checks for Headers                                -->
  <!-- See https://checkstyle.org/checks/header/index.html   -->
  <!-- <module name="Header"> -->
  <!--   <property name="headerFile" value="${checkstyle.header.file}"/> -->
  <!--   <property name="fileExtensions" value="java"/> -->
  <!-- </module> -->

  <module name="TreeWalker">

    <!-- Checks for Javadoc comments.                     -->
    <!-- See https://checkstyle.org/checks/javadoc/index.html -->
    <module name="InvalidJavadocPosition" />
    <module name="JavadocMethod" />
    <module name="JavadocType" />
    <module name="JavadocVariable" />
    <module name="JavadocStyle" />
    <module name="MissingJavadocType">
      <property name="scope" value="protected" />
    </module>
    <module name="MissingJavadocMethod">
      <property name="scope" value="protected" />
    </module>

    <!-- Checks for Naming Conventions.                  -->
    <!-- See https://checkstyle.org/checks/naming/index.html -->
    <module name="ConstantName" />
    <module name="LocalFinalVariableName" />
    <module name="LocalVariableName" />
    <module name="MemberName" />
    <module name="MethodName" />
    <module name="PackageName" />
    <module name="ParameterName" />
    <module name="StaticVariableName" />
    <module name="TypeName" />

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

    <!-- Checks for Size Violations.                    -->
    <!-- See https://checkstyle.org/checks/sizes/index.html -->
    <module name="MethodLength" />
    <module name="ParameterNumber" />

    <!-- Checks for whitespace                               -->
    <!-- See https://checkstyle.org/checks/whitespace/index.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/checks/modifier/index.html -->
    <module name="ModifierOrder" />
    <module name="RedundantModifier" />

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

    <!-- Checks for common coding problems               -->
    <!-- See https://checkstyle.org/checks/coding/index.html -->
    <module name="EmptyStatement" />
    <module name="EqualsHashCode" />
    <module name="HiddenField">
      <property name="ignoreConstructorParameter" value="true" />
    </module>
    <module name="IllegalInstantiation" />
    <module name="InnerAssignment" />
    <module name="MagicNumber" />
    <module name="MissingSwitchDefault" />
    <module name="MultipleVariableDeclarations" />
    <module name="SimplifyBooleanExpression" />
    <module name="SimplifyBooleanReturn" />

    <!-- Checks for class design                         -->
    <!-- See https://checkstyle.org/checks/design/index.html -->
    <module name="DesignForExtension" />
    <module name="FinalClass" />
    <module name="HideUtilityClassConstructor" />
    <module name="InterfaceIsType" />
    <module name="VisibilityModifier" />

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

    <!-- https://checkstyle.org/filters/suppressionxpathfilter.html -->
    <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>