src/conf/checkstyle/checkstyle.xml

<?xml version="1.0"?>
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contributor license agreements.  See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
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     https://www.apache.org/licenses/LICENSE-2.0

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-->
<!DOCTYPE module PUBLIC
    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
    "https://checkstyle.org/dtds/configuration_1_3.dtd">
<!-- commons lang customization of default Checkstyle behavior -->
<module name="Checker">
  <property name="localeLanguage" value="en" />
  <module name="JavadocPackage">
    <!-- setting allowLegacy means it will check for package.html instead of just package-info.java -->
    <property name="allowLegacy" value="true" />
  </module>
  <module name="FileTabCharacter">
    <property name="fileExtensions" value="java,xml" />
  </module>
  <module name="TreeWalker">
    <module name="ExplicitInitializationCheck" />
    <module name="AvoidStarImport" />
    <module name="RedundantImport" />
    <module name="MagicNumber" />
    <module name="ModifierOrder" />
    <module name="SuppressionCommentFilter" />
    <module name="UnusedImports" />
    <module name="NeedBraces" />
    <module name="ParenPad" />
    <module name="JavadocMethod">
      <property name="accessModifiers" value="protected, public" />
    </module>
    <module name="ImportOrder">
      <property name="option" value="top" />
      <property name="groups" value="java,javax,org" />
      <property name="ordered" value="true" />
      <property name="separated" value="true" />
    </module>
    <module name="TypecastParenPad" />    
  </module>
  <module name="RegexpSingleline">
    <!-- @author tags are deprecated -->
    <property name="format" value="^\s+\*\s+@author\s" />
    <property name="message" value="Deprecated @author tag" />
    <property name="fileExtensions" value="java" />
    <property name="severity" value="warning" />
  </module>
  <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>