checkstyle.xml

<?xml version="1.0"?>

<!--
   Licensed to the Apache Software Foundation (ASF) under one or more
  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
  the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
  -->

<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.1//EN" "http://www.puppycrawl.com/dtds/configuration_1_1.dtd">

<!-- commons math customization of default Checkstyle behavior -->
<module name="Checker">
  <property name="localeLanguage" value="en"/>

  <module name="TreeWalker">

    <!-- Operator must be at end of wrapped line -->
    <module name="OperatorWrap">
      <property name="option" value="eol"/>
    </module>

    <!-- No if/else/do/for/while without braces -->
    <module name="NeedBraces"/>

    <!-- Interfaces must be types (not just constants) -->
    <module name="InterfaceIsType"/>

    <!-- Must have class / interface header comments -->
    <module name="JavadocType"/>
        
     <!-- Require method javadocs, allow undeclared RTE -->
    <module name="JavadocMethod">
      <property name="allowUndeclaredRTE" value="true"/>
      <property name="allowThrowsTagsForSubclasses" value="true"/>
      <property name="validateThrows" value="false"/>
    </module>

    <!-- Require field javadoc -->
    <module name="JavadocVariable"/>
        
    <!-- No public fields -->
    <module name="VisibilityModifier">
       <property name="protectedAllowed" value="true"/>
    </module>

    <!-- Require hash code override when equals is -->
    <module name="EqualsHashCode"/>
    
    <!-- Disallow unnecessary instantiation of Boolean, String -->
    <module name="IllegalInstantiation">
      <property name="classes" value="java.lang.Boolean, java.lang.String"/>
    </module>

    <!-- Required for SuppressionCommentFilter below -->
    <module name="FileContentsHolder"/>
 
    <!--  Import should be explicit, really needed and only from pure java packages -->
    <module name="AvoidStarImport" />
    <module name="UnusedImports" />
    <module name="IllegalImport" />

    <!-- Utility class should not be instantiated, they must have a private constructor -->
    <module name="HideUtilityClassConstructor" />

    <!-- Switch statements should be complete and with independent cases -->
    <module name="FallThrough" />
    <module name="MissingSwitchDefault" />

    <!-- Constant names should obey the traditional all uppercase naming convention -->
    <module name="ConstantName" />

    <!-- Method parameters and local variables should not hide fields, except in constructors and setters -->
    <module name="HiddenField">
        <property name="ignoreConstructorParameter" value="true" />
        <property name="ignoreSetter" value="true" />
    </module>
    
    <!-- No trailing whitespace -->
    <module name="Regexp">
      <property name="format" value="[ \t]+$"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="Trailing whitespace"/>
    </module>
    
    <!-- No System.out.println() statements -->
    <module name="Regexp">
      <!-- no sysouts -->
      <property name="format" value="System\.out\.println"/>
      <property name="illegalPattern" value="true"/>
    </module>

    <!-- Authors should be in pom.xml file -->
    <module name="Regexp">
      <property name="format" value="@author"/>
      <property name="illegalPattern" value="true"/>
      <property name="message" value="developers names should be in pom file"/>
    </module>

    <!-- Use a consistent way to put modifiers -->
    <module name="RedundantModifier" />
    <module name="ModifierOrder" />

    <!-- Use a consistent way to put declarations -->
    <module name="DeclarationOrder" />

    <!-- Don't add up parentheses when they are not required -->
    <module name="UnnecessaryParentheses" />

    <!--  Don't use too widespread catch (Exception, Throwable, RuntimeException)  -->
    <module name="IllegalCatch" />

    <!-- Don't use = or != for string comparisons -->
    <module name="StringLiteralEquality" />
 
   <!-- Don't declare multiple variables in the same statement -->
    <module name="MultipleVariableDeclarations" />

    <!-- String literals more than one character long should not be repeated several times -->
    <!-- the "unchecked" string is also accepted to allow @SuppressWarnings("unchecked") -->
    <module name="MultipleStringLiterals" >
      <property name="ignoreStringsRegexp" value='^(("")|(".")|("unchecked"))$'/>
    </module>

    <!-- <module name="TodoComment" /> -->

  </module>

  <!-- Verify that EVERY source file has the appropriate license -->
  <module name="Header">
    <property name="headerFile" value="${checkstyle.header.file}"/>
  </module>

  <!-- No tabs allowed! -->
  <module name="FileTabCharacter"/>

  <!-- Require files to end with newline characters -->
  <module name="NewlineAtEndOfFile"/>
  
  <!-- Require package javadoc -->
  <module name="JavadocPackage"/>

  <!-- Setup special comments to suppress specific checks from source files -->
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop JavadocVariable"/>
    <property name="onCommentFormat"  value="CHECKSTYLE\: resume JavadocVariable"/>
    <property name="checkFormat"      value="JavadocVariable"/>
  </module>
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop JavadocMethodCheck"/>
    <property name="onCommentFormat"  value="CHECKSTYLE\: resume JavadocMethodCheck"/>
    <property name="checkFormat"      value="JavadocMethodCheck"/>
  </module>
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop ConstantName"/>
    <property name="onCommentFormat"  value="CHECKSTYLE\: resume ConstantName"/>
    <property name="checkFormat"      value="ConstantName"/>
  </module>
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop HideUtilityClassConstructor"/>
    <property name="onCommentFormat"  value="CHECKSTYLE\: resume HideUtilityClassConstructor"/>
    <property name="checkFormat"      value="HideUtilityClassConstructor"/>
  </module>
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop MultipleVariableDeclarations"/>
    <property name="onCommentFormat"  value="CHECKSTYLE\: resume MultipleVariableDeclarations"/>
    <property name="checkFormat"      value="MultipleVariableDeclarations"/>
  </module>
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop IllegalCatch"/>
    <property name="onCommentFormat"  value="CHECKSTYLE\: resume IllegalCatch"/>
    <property name="checkFormat"      value="IllegalCatch"/>
  </module>
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop DeclarationOrder"/>
    <property name="onCommentFormat"  value="CHECKSTYLE\: resume DeclarationOrder"/>
    <property name="checkFormat"      value="DeclarationOrder"/>
  </module>
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop RedundantModifier"/>
    <property name="onCommentFormat"  value="CHECKSTYLE\: resume RedundantModifier"/>
    <property name="checkFormat"      value="RedundantModifier"/>
  </module>
  <module name="SuppressionCommentFilter">
    <property name="offCommentFormat" value="CHECKSTYLE\: stop all"/>
    <property name="onCommentFormat" value="CHECKSTYLE\: resume all"/>
  </module>
</module>