Implementing PMD 6.x, CPD, Checkstyle 3.x, JavaSources 3.x, JavaDocs 3.x, Findbugs 3.x or SpotBugs 4.x using maven

We all know the importance of static code analysis in software development. Static code analysis checks the source code files of an application without actually running the application. It validates the coding standards and required code style. It is very helpful during code review as well.

There are several Open source tools available which does static code analysis. Most popular ones are PMD, CPD (combined with pmd), Checkstyle, Findbugs and many more.

I have been using using PMD 5.x, CPD 5.x (combined with pmd), Checkstyle 2.x and FindBugs 2.x in combination for past 4-5 years.

I have a post on PMD5.x here if you want to check it out:
https://javaworld-abhinav.blogspot.com/2016/02/implement-pmd-findbugs-code-coverage.html


Open source and code quality enthusiasts has been contributing for these tools over the years and these tools are now very much intelligent and helping in delivering good quality code.

PMD on the other has been revamped alot and has more granular rule-sets.

You can see more on PMD here: https://pmd.github.io/latest/#overview

We can configure all the plugins (PMD, CPD, FindBugs, JavaSources and JavaDocs) as part of build life (default) cycle as well as site life cycle. Here we will see both.

There are 3 standard life cycles in maven. Clean, Build and Site.

In general,

1. clean (which includes pre-clean,clean and post-clean) life cycle is used to clean the build directory.
2. build (the default) life cycle (which includes validate, initialize, generate-sources, compile, test, package, verify, install and deploy etc.) used to build artifacts. It is the default life cycle in maven.
3. site (which includes pre-site,site-post-site and site-deploy) lifecycle is used to create fresh documentation to create reports, deploy site etc.

If you want to know more  about maven life-cycles then refer below given link:

https://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html

Prerequisites: You will need following plug-ins in order to implement PMD, CPD, FindBugs, JavaDocs, JavaSources and Java code coverage.

  JavaDocs:

1. maven-javadoc-plugin (version 3.1.1)

  JavaSources:

1. maven-source-plugin (version 3.2.0)

  PMD:

1. maven-jxr-plugin (version 3.0.0)
2. maven-pmd-plugin (version 3.12.0)

  FindBugs (Below Java9):

1. findbugs-maven-plugin (version 3.0.5)

 SpotBugs (Java9 onwards):

1. spotbugs-maven-plugin (version 3.1.12.2)
2. spotbugs (4.0.0-beta4)

Post java9, findbugs is no longer maintained and we need to use spotbugs. It is successor of findbugs.

 Checkstyles:

1. maven-checkstyle-plugin (version 3.1.0)

 Other Plugins to support build and reporting:

1. maven-resources-plugin (version 3.0.1)
2. maven-project-info-reports-plugin (version 2.7)
3. maven-surefire-report-plugin (version 3.0.0-M3)
4. maven-site-plugin (version 3.8.2)

Note: Using latest version of maven-project-info-reports-plugin (i.e. 3.0.0) doesn't work. Seems there are some bugs as using these plugin versions you get 

java.lang.NoClassDefFoundError: org/apache/maven/doxia/siterenderer/DocumentContent

Optional Plugins:

1. maven-compiler-plugin (version 3.8.1) -- we need to override the maven compiler plug-in to set JDK version if your code is written in JDK 7 and above

To execute all plugins together you can run following command: mvn install site

Note: If you are getting 'java.lang.OutOfMemoryError: PermGen space' during the build then you have to set "MAVEN_OPTS=-XX:MaxPermSize=1024m".

If you are using eclipse you can set argument in 'VM Arguments' while running the maven command.

Configuring Java Sources maven plug-in:

This plug-in will generate a jar file containing the source code.

<!-- Java sources plug-in-->
<plugin>
 <groupId>org.apache.maven.plugins</groupId>
 <artifactId>maven-source-plugin</artifactId>
 <version>3.2.0</version>
 <executions>
  <execution>
   <id>attach-sources</id>
   <goals>
    <goal>jar-no-fork</goal>
   </goals>
  </execution>
 </executions>
</plugin>

Configuring Java Docs maven plug-in: 

<!-- JavaDocs configuration-->
<plugin>
 <groupId>org.apache.maven.plugins</groupId>
 <artifactId>maven-resources-plugin</artifactId>
 <version>3.0.1</version>
 <executions>
  <execution>
   <id>copy static resource files</id>
   <phase>generate-sources</phase>
   <goals>
    <goal>resources</goal>
   </goals>
  </execution>
 </executions>
</plugin>

<plugin>
 <groupId>org.apache.maven.plugins</groupId>
 <artifactId>maven-javadoc-plugin</artifactId>
 <version>3.1.1</version>
 <executions>
  <execution>
   <id>attach-javadocs</id>
   <goals>
    <goal>jar</goal>
   </goals>
  </execution>
 </executions>
</plugin>

Configuring FindBugs maven plugin (Use this if you are using java8 or below): 

Here we are configuring findbugs into build lifecycle under 'package' phage. See <phase> element inside <executions>/<execution> element. The <plugins> element is configured under <build> element which means the plugin will be executed during build (life cycle) process.

To run findbugs you can use following command:

mvn findbugs:findbugs 

If you want to run findbugs and want the build to fail if violations are found, then you can use following command:

mvn findbugs:check

To see usage details on findbugs you can refer below website:

http://gleclaire.github.io/findbugs-maven-plugin/usage.html

<!-- FindBugs Integration, you can also run it directly using mvn findbugs:findbugs or findbugs:check -->
<plugin>
 <groupId>org.codehaus.mojo</groupId>
 <artifactId>findbugs-maven-plugin</artifactId>
 <version>3.0.5</version>
 <configuration>
  <!-- FindBugs will show what is doing during analysis. -->
  <debug>false</debug>
  <!-- Enables analysis which takes more memory but finds more bugs. If 
      you run out of memory, changes the value of the effort element to 'min'. 
      Min|Default|Max are possible values. -->
  <effort>Min</effort>
  <!-- Reports all bugs (other values are High|Normal|Low|Exp|Ignore) -->
  <threshold>High</threshold>
  <xmlOutput>true</xmlOutput>
  <!-- Optional directory to save findbugs xdoc xml report -->
  <xmlOutputDirectory>${project.reporting.outputDirectory}</xmlOutputDirectory>
  <!-- Indicates to analyze only given java packages, We are allowing everything here. -->
  <!-- <onlyAnalyze>com.*</onlyAnalyze> -->  
  <failOnError>true</failOnError>
 </configuration>
 <executions>
  <execution>
   <phase>package</phase>
   <goals>
    <!-- This goal will check code and generate report -->
    <!--<goal>findbugs</goal>-->
    <!-- Fail the build if there were any findBugs violations in the source code. Uncomment if needed -->
    <!-- This goal includes both findbugs and check -->
    <goal>check</goal>
   </goals>
  </execution>
 </executions>
</plugin>

Configuring SpotBugs maven plugin (Use this if you are using Java9 or above): 

Post java9, findbugs is no longer maintained and we need to use spotbugs. It is successor of findbugs.

SpotBugs looks for bugs in Java programs. It is based on the concept of bug patterns. A bug pattern is a code idiom that is often an error. 

Bug patterns arise for a variety of reasons: 

- Difficult language features 

- Misunderstood API methods 

- Misunderstood invariants when code is modified during maintenance 

- Garden variety mistakes: typos, use of the wrong boolean operator

<plugin>
  <groupId>com.github.spotbugs</groupId>
  <artifactId>spotbugs-maven-plugin</artifactId>
  <version>3.1.12.2</version>
  <dependencies>
 <!-- overwrite dependency on spotbugs if you want to specify the version of spotbugs -->
 <dependency>
   <groupId>com.github.spotbugs</groupId>
   <artifactId>spotbugs</artifactId>
   <version>4.0.0-beta4</version>
 </dependency>
  </dependencies>
  <configuration>
 <!-- SpotBugs will show what is doing during analysis. -->
 <debug>false</debug>
 <!-- Enables analysis which takes more memory but finds more bugs. If 
  you run out of memory, changes the value of the effort element to 'min'. 
  Min|Default|Max are possible values. -->
 <effort>Min</effort>
 <!-- Reports all bugs (other values are High|Normal|Low|Exp|Ignore) -->
 <threshold>High</threshold>
 <xmlOutput>true</xmlOutput>
 <!-- Optional directory to save SpotBugs xdoc xml report -->
 <xmlOutputDirectory>${project.reporting.outputDirectory}</xmlOutputDirectory>
 <!-- Stops the build if violation found -->
 <failOnError>true</failOnError>
 <!-- Indicates to analyze only given java packages, We are allowing everything here. -->
 <!-- <onlyAnalyze>com.*</onlyAnalyze> -->  
 </configuration>
  <executions>
 <execution>
  <phase>package</phase>
  <goals>
   <!-- spotbugs goal analyses target project by SpotBugs -->
   <!-- <goal>spotbugs</goal> -->
   <!-- check goal runs analysis like spotbugs goal, and make the build failed if it found any bugs. -->
   <goal>check</goal>
  </goals>
 </execution>
  </executions>
</plugin>

Configuring PMD and CPD maven plug-in: 

Here we are configuring pmd into build lifecycle under 'package' phage. See <phase> element inside <executions>/<execution> element. The <plugins> element is configured under <build> element which means the plugin will be executed during build (life cycle) process.

To run pmd you can use following command: mvn pmd:pmd  

To run cpd you can use following command: mvn pmd:cpd

If you want to run pmd and want the build to fail if violations are found, then you can use following command: mvn pmd:check

If you want to run cpd and want the build to fail if violations are found, then you can use following command: mvn pmd:cpd-check

For more details on pmd configuration options you can look here:

https://maven.apache.org/plugins/maven-pmd-plugin/pmd-mojo.html

<!-- PMD Integration, you can also run it directly using mvn pmd:pmd or pmd:check -->
<plugin>
 <groupId>org.apache.maven.plugins</groupId>
 <artifactId>maven-jxr-plugin</artifactId>
 <version>3.0.0</version>
 <executions>
  <execution>
   <phase>package</phase>
   <goals>
    <goal>jxr</goal>
   </goals>
  </execution>
 </executions>
</plugin>

<plugin>
 <groupId>org.apache.maven.plugins</groupId>
 <artifactId>maven-pmd-plugin</artifactId>
 <version>3.12.0</version>
 <configuration>
  <!-- Run PMD on the tests. Default: false -->
  <includeTests>false</includeTests>

  <!-- Link the violation line numbers to the source xref. Links will 
    be created automatically if the jxr plugin is being used. Default: true -->
  <linkXRef>true</linkXRef>

  <!--Set the output format type, in addition to the HTML report. Must 
   be one of: "none", "csv", "xml", "txt" or the full class name of the PMD 
   renderer to use. See the net.sourceforge.pmd.renderers package javadoc for 
   available renderers. XML is required if the pmd:check goal is being used. 
   Default: xml -->
  <format>xml</format>

  <!-- Skip the PMD checks. Most useful on the command line via "-Dpmd.skip=true" -->
  <skip>false</skip>

  <!-- Print details of check failures to build output. -->
  <verbose>true</verbose>

  <!-- A list of files to include from checking. Can contain Ant-style 
    wildcards and double wildcards. Defaults to **\/*.java. -->
  <includes>
   <include>com/**/*.java</include>
  </includes>

  <!-- Fail build if there are high priority warnings during pmd:check. 
    Default value is 5 -->
  <failurePriority>1</failurePriority>

  <!-- A list of files to exclude from checking. Can contain Ant-style 
    wildcards and double wildcards. We are not excluding anything here. -->
  <!-- <excludes> 
    <exclude></exclude>
    </excludes> 
      -->

  <!-- The output directory for the final HTML report. -->
  <outputDirectory>${project.reporting.outputDirectory}</outputDirectory>

  <!-- The output directory for the intermediate XML report. -->
  <targetDirectory>${project.build.directory}</targetDirectory>

  <rulesets>
   <!-- Multiple rule set xmls can be included here. -->
   <ruleset>${basedir}/pmd_ruleset.xml</ruleset>
  </rulesets>
 </configuration>
 <executions>
  <execution>
   <phase>package</phase>
   <goals>
    <!-- Creates a PMD report. -->
    <!--<goal>pmd</goal> -->
    <!-- Fail the build if there were any PMD violations in the source code. -->
    <goal>check</goal>
    <!-- Creates a report for PMD's copy paste detector tool -->
    <goal>cpd</goal>
    <!-- Fail the build if there were any CPD violations in the source code. Uncomment if needed -->
    <!-- <goal>cpd-check</goal> -->
   </goals>
  </execution>
 </executions>
</plugin>

PMD Ruleset configuration as per version 6.13.0 (pmd_ruleset.xml):

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<ruleset xmlns="http://pmd.sf.net/ruleset/1.0.0" name=""
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:noNamespaceSchemaLocation="http://pmd.sf.net/ruleset_xml_schema.xsd"
 xsi:schemaLocation="http://pmd.sf.net/ruleset/1.0.0 http://pmd.sf.net/ruleset_xml_schema.xsd">
 <description>
  <![CDATA[
      This ruleset is as per version 6.13.0
      PMD Plugin preferences rule set
   Priority means: 1 – error, high priority, 2 – error,
   normal priority, 3 – warning, high priority, 4 – warning, normal priority and 5 – information.
  ]]>
 </description>
 <rule ref="category/java/codestyle.xml/PrematureDeclaration">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/ShortVariable">
  <priority>1</priority>
  <properties>
           <property name="minimum" value="3" />
  </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/LongVariable">
  <priority>4</priority>
  <properties>
      <property name="minimum" value="45" />
  </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/ShortMethodName">
  <priority>1</priority>
  <properties>
     <property name="minimum" value="3" />
  </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/FieldNamingConventions">
  <priority>1</priority>
  <properties>
         <property name="publicConstantPattern" value="[A-Z][A-Z_0-9]*" />
         <property name="constantPattern" value="[A-Z][A-Z_0-9]*" />
         <property name="enumConstantPattern" value="[A-Z][A-Z_0-9]*" />
         <property name="finalFieldPattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="staticFieldPattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="defaultFieldPattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="exclusions" value="serialVersionUID|serialPersistentFields" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/LocalVariableNamingConventions">
  <priority>1</priority>
  <properties>
          <property name="localVarPattern" value="[a-z][a-zA-Z0-9]*" />
          <property name="finalVarPattern" value="[a-z][a-zA-Z0-9]*" />
          <property name="catchParameterPattern" value="[a-z][a-zA-Z0-9]*" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/FormalParameterNamingConventions">
  <priority>1</priority>
  <properties>
         <property name="methodParameterPattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="finalMethodParameterPattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="lambdaParameterPattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="explicitLambdaParameterPattern" value="[a-z][a-zA-Z0-9]*" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/MethodNamingConventions">
  <priority>1</priority>
  <properties>
         <property name="methodPattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="staticPattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="nativePattern" value="[a-z][a-zA-Z0-9]*" />
         <property name="junit3TestPattern" value="test[A-Z0-9][a-zA-Z0-9]*" />
         <property name="junit4TestPattern" value="[a-z][a-zA-Z0-9]*" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/ClassNamingConventions">
  <priority>1</priority>
  <properties>
         <property name="classPattern" value="[A-Z][a-zA-Z0-9]*" />
         <property name="abstractClassPattern" value="[A-Z][a-zA-Z0-9]*" />
         <property name="interfacePattern" value="[A-Z][a-zA-Z0-9]*" />
         <property name="enumPattern" value="[A-Z][a-zA-Z0-9]*" />
         <property name="annotationPattern" value="[A-Z][a-zA-Z0-9]*" />
         <property name="utilityClassPattern" value="(^Assocs$)|(^Prop$)|([A-Z][a-zA-Z0-9]+(Utils?|Utility?|Helper?|Constants?|Model?|Aspect?|Type?|Object?|Override?|Mandatory?))" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/ShortClassName">
  <priority>1</priority>
     <properties>
         <property name="minimum" value="4" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/LinguisticNaming">
  <priority>1</priority>
     <properties>
         <property name="ignoredAnnotations" value="java.lang.Override" />
         <property name="checkBooleanMethod" value="true" />
         <property name="checkGetters" value="true" />
         <property name="checkSetters" value="true" />
         <property name="checkPrefixedTransformMethods" value="true" />
         <property name="checkTransformMethods" value="false" />
         <property name="booleanMethodPrefixes" value="is|has|can|have|will|should" />
         <property name="transformMethodNames" value="to|as" />
         <property name="checkFields" value="true" />
         <property name="checkVariables" value="true" />
         <property name="booleanFieldPrefixes" value="is|has|can|have|will|should" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/GenericsNaming">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/IdenticalCatchBranches">
  <priority>1</priority>
 </rule> 
 <rule ref="category/java/codestyle.xml/CommentDefaultAccessModifier">
  <priority>1</priority>
  <![CDATA[
     final String stringValueBad = "some string value"; 
   /* default */ final String stringValueGood = "some string"; <-- should be this way
  ]]>
 </rule>
 <rule ref="category/java/codestyle.xml/AvoidDollarSigns">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/NoPackage">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/PackageCase">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/BooleanGetMethodName">
  <priority>1</priority>
  <properties>
           <property name="checkParameterizedMethods" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/UseUtilityClass">
  <priority>1</priority>

  <!-- Ignore check for spring boot application -->
  <properties>
       <property name="violationSuppressXPath" value="//ClassOrInterfaceDeclaration/preceding-sibling::Annotation/MarkerAnnotation/Name[@Image='SpringBootApplication']" />
  </properties>
 </rule>
 <rule ref="category/java/design.xml/SimplifyBooleanReturns">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/SimplifyBooleanExpressions">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/SimplifiedTernary">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/SwitchStmtsShouldHaveDefault">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/design.xml/AvoidDeeplyNestedIfStmts">
  <priority>3</priority>
  <properties>
         <property name="problemDepth" value="6" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/AvoidReassigningParameters">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/design.xml/SwitchDensity">
  <priority>3</priority>
  <properties>
           <property name="minimum" value="10.0"/>
         </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/AccessorClassGeneration">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/AccessorMethodGeneration" >
  <priority>3</priority>
 </rule>
 <rule ref="category/java/design.xml/FinalFieldCouldBeStatic">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/DefaultLabelNotLastInSwitchStmt">
  <priority>4</priority>
 </rule>
 <!-- Configure this rule when using PMD 6.16.0 -->
 <!-- <rule ref="category/java/bestpractices.xml/DoubleBraceInitialization">
  <priority>3</priority>
 </rule> -->
 <rule ref="category/java/bestpractices.xml/ForLoopCanBeForeach">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/ForLoopVariableCount">
  <priority>3</priority>
  <properties>
           <property name="maximumVariables" value="1" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/GuardLogStatement">
  <priority>3</priority>
     <properties>
      <!-- Allow info and isInfoEnabled to be ignored and rest of them will be checked -->
         <property name="logLevels" value="trace,debug,warn,error,log,finest,finer,fine,warning,severe" />
         <property name="guardsMethods" value="isTraceEnabled,isDebugEnabled,isWarnEnabled,isErrorEnabled,isLoggable" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/ImmutableField">
  <priority>1</priority>
  <properties>
         <property name="ignoredAnnotations" value="lombok.Setter|lombok.Getter|lombok.Builder|lombok.Data|lombok.RequiredArgsConstructor|lombok.AllArgsConstructor|lombok.Value|lombok.NoArgsConstructor" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/LawOfDemeter">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/AvoidProtectedFieldInFinalClass">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/AvoidProtectedMethodInFinalClassNotExtending">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/AbstractClassWithoutAbstractMethod">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/SimplifyConditional">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/PositionLiteralsFirstInComparisons">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/PositionLiteralsFirstInCaseInsensitiveComparisons">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/UnnecessaryLocalBeforeReturn">
  <priority>1</priority>
  <properties>
         <property name="statementOrderMatters" value="true" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/ConstantsInInterface">
  <priority>1</priority>
  <properties>
          <property name="ignoreIfHasMethods" value="true" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml">
  <exclude name="ConfusingTernary" />
 </rule>
 <rule ref="category/java/codestyle.xml/ControlStatementBraces">
  <priority>1</priority>
     <properties>
         <property name="checkIfElseStmt" value="true" />
         <property name="checkSingleIfStmt" value="true" />
         <property name="checkWhileStmt" value="true" />
         <property name="checkForStmt" value="true" />
         <property name="checkDoWhileStmt" value="true" />
         <property name="checkCaseStmt" value="false" />
         <property name="allowEmptyLoop" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/UseCollectionIsEmpty">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/UseTryWithResources">
  <priority>1</priority>
     <properties>
         <property name="closeMethods" value="close,closeQuietly" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/UseVarargs">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/WhileLoopWithLiteralBoolean">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/PreserveStackTrace">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/ClassWithOnlyPrivateConstructorsShouldBeFinal">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/EmptyMethodInAbstractClassShouldBeAbstract">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/SingularField">
  <priority>1</priority>
  <properties>
         <property name="ignoredAnnotations" value="lombok.Setter|lombok.Getter|lombok.Builder|lombok.Data|lombok.RequiredArgsConstructor|lombok.AllArgsConstructor|lombok.Value|lombok.NoArgsConstructor|lombok.experimental.Delegate" />
         <property name="checkInnerClasses" value="false" />
         <property name="disallowNotAssignment" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/AbstractClassWithoutAnyMethod">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/FieldDeclarationsShouldBeAtStartOfClass">
  <priority>1</priority>
  <properties>
         <property name="ignoreEnumDeclarations" value="true" />
         <property name="ignoreAnonymousClassDeclarations" value="true" />
         <property name="ignoreInterfaceDeclarations" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/SignatureDeclareThrowsException">
  <priority>3</priority>
  <properties>
         <property name="IgnoreJUnitCompletely" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/ExceptionAsFlowControl">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/design.xml/AvoidThrowingRawExceptionTypes">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/AvoidUncheckedExceptionsInSignatures">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/design.xml/AvoidThrowingNullPointerException">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/AvoidRethrowingException">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/DoNotExtendJavaLangError">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/AvoidThrowingNewInstanceOfSameException">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/AvoidCatchingGenericException">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/UnusedPrivateField">
  <priority>1</priority>
     <properties>
         <property name="ignoredAnnotations" value="lombok.Setter|lombok.Getter|lombok.Builder|lombok.Data|lombok.RequiredArgsConstructor|lombok.AllArgsConstructor|lombok.Value|lombok.NoArgsConstructor|java.lang.Deprecated|javafx.fxml.FXML|lombok.experimental.Delegate" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/UnusedLocalVariable">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/UnusedPrivateMethod">
  <priority>1</priority>
     <properties>
         <property name="ignoredAnnotations" value="java.lang.Deprecated" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/UnusedFormalParameter">
  <priority>1</priority>
  <properties>
          <property name="checkAll" value="true" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/SystemPrintln">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/AvoidPrintStackTrace">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/AvoidReassigningLoopVariables">
  <priority>1</priority>
     <properties>
         <property name="foreachReassign" value="deny" />
         <property name="forReassign" value="deny" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/AvoidStringBufferField">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/ReplaceVectorWithList">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/ReplaceHashtableWithMap">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/ReplaceEnumerationWithIterator">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/JUnit4TestShouldUseBeforeAnnotation">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/JUnit4TestShouldUseAfterAnnotation">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/JUnit4TestShouldUseTestAnnotation">
  <priority>3</priority>
  <properties>
          <property name="testClassPattern" value="Test" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/JUnit4SuitesShouldUseSuiteAnnotation">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/JUnitUseExpected">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/MDBAndSessionBeanNamingConvention">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/RemoteSessionInterfaceNamingConvention">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/LocalInterfaceSessionNamingConvention">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/LocalHomeNamingConvention">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/RemoteInterfaceNamingConvention">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/MethodArgumentCouldBeFinal">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/LocalVariableCouldBeFinal">
  <priority>1</priority>
  <properties>
         <property name="ignoreForEachDecl" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/UnnecessaryReturn">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/UnnecessaryModifier">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/UseDiamondOperator">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/design.xml/UselessOverridingMethod">
  <priority>1</priority>
  <properties>
         <property name="ignoreAnnotations" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/UseObjectForClearerAPI">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/ForLoopShouldBeWhileLoop">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/CollapsibleIfStatements">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/AvoidUsingHardCodedIP">
  <priority>3</priority>
  <properties>
           <property name="checkAddressTypes" value="IPv4 mapped IPv6|IPv6|IPv4" />
       </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/CheckResultSet">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/ExtendsObject">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/MethodReturnsInternalArray">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/MissingOverride">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/ArrayIsStoredDirectly">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/OneDeclarationPerLine">
  <priority>1</priority>
     <properties>
         <property name="strictMode" value="false" />
     </properties>
 </rule>
 <!-- Configure this rule when using PMD 6.18.0 -->
 <!-- <rule ref="category/java/bestpractices.xml/AvoidMessageDigestField">
  <priority>3</priority>
 </rule> -->
 <rule ref="category/java/design.xml/CouplingBetweenObjects">
  <priority>3</priority>
  <properties>
         <property name="threshold" value="20" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/ExcessiveImports">
  <priority>3</priority>
  <properties>
         <property name="minimum" value="30.0" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/LooseCoupling">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/DuplicateImports">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/DontImportJavaLang">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/UnusedImports">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/UnnecessaryFullyQualifiedName">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/TooManyStaticImports">
  <priority>3</priority>
  <properties>
         <property name="maximumStaticImports" value="10" />
     </properties>
 </rule>
 <rule ref="category/java/codestyle.xml/UnnecessaryAnnotationValueElement">
  <![CDATA[
      @TestClassAnnotation(value = "TEST")
   public class Foo {
       @TestMemberAnnotation(value = "TEST")
       private String y;
   
       @TestMethodAnnotation(value = "TEST")
       public void bar() {
           int x = 42;
           return;
       }
   }
   
   // should be
   @TestClassAnnotation("TEST")
   public class Foo {
       @TestMemberAnnotation("TEST")
       private String y;
   
       @TestMethodAnnotation("TEST")
       public void bar() {
           int x = 42;
           return;
       }
   }
  ]]>  
  <priority>1</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/JUnitAssertionsShouldIncludeMessage">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/JUnitTestContainsTooManyAsserts">
  <priority>3</priority>
     <properties>
         <property name="maximumAsserts" value="3" />
     </properties>
 </rule>
 <rule ref="category/java/bestpractices.xml/JUnitTestsShouldIncludeAssert">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/UseAssertEqualsInsteadOfAssertTrue">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/UseAssertSameInsteadOfAssertTrue">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/UseAssertTrueInsteadOfAssertEquals">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/bestpractices.xml/UseAssertNullInsteadOfAssertTrue">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/design.xml/SimplifyBooleanAssertion">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/OnlyOneReturn">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/CallSuperInConstructor">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/UselessParentheses">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/DefaultPackage">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/UseUnderscoresInNumericLiterals">
  <priority>4</priority>
     <properties>
         <property name="acceptableDecimalLength" value="4" />
     </properties>
 </rule>
 <!-- Configure this rule when using PMD 6.15.0 -->
 <!-- <rule ref="category/java/codestyle.xml/UseShortArrayInitializer">
  <priority>3</priority>
 </rule> -->
 <rule ref="category/java/codestyle.xml/UselessQualifiedThis">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/codestyle.xml/AvoidUsingNativeCode">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/codestyle.xml">
  <exclude name="UnnecessaryConstructor" />
  <exclude name="AtLeastOneConstructor"/>
 </rule>
 <rule ref="category/java/design.xml/NPathComplexity">
  <priority>3</priority>
  <properties>
         <property name="reportLevel" value="200" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/ExcessiveClassLength">
  <priority>3</priority>
  <properties>
         <property name="minimum" value="2000.0" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/ExcessiveMethodLength">
  <priority>3</priority>
  <properties>
         <property name="minimum" value="150.0" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/ExcessiveParameterList">
  <priority>3</priority>
     <properties>
         <property name="minimum" value="10.0" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/CyclomaticComplexity">
  <priority>4</priority>
  <properties>
         <property name="classReportLevel" value="80" />
         <property name="methodReportLevel" value="10" />
         <property name="cycloOptions" value="" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/DataClass">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/design.xml/ExcessivePublicCount">
  <priority>3</priority>
  <properties>
         <property name="minimum" value="45.0" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/GodClass">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/design.xml/LogicInversion">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/design.xml/LoosePackageCoupling">
  <priority>4</priority>
  <!-- Configure allowed classes and packages here -->
     <!-- <properties>
         <property name="packages" value="" />
         <property name="classes" value="" />
     </properties> -->
 </rule>
 <rule ref="category/java/design.xml/TooManyFields">
  <priority>3</priority>
  <properties>
          <property name="maxfields" value="15" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/NcssCount">
  <priority>3</priority>
     <properties>
         <property name="methodReportLevel" value="60" />
         <property name="classReportLevel" value="1500" />
         <property name="ncssOptions" value="" />
     </properties>
 </rule>
 <rule ref="category/java/design.xml/TooManyMethods">
  <priority>3</priority>
  <properties>
          <property name="maxmethods" value="10" />
    </properties>
 </rule>
 <rule ref="category/java/documentation.xml/CommentContent">
  <priority>1</priority>
     <properties>
         <property name="caseSensitive" value="false" />
         <property name="disallowedTerms" value="idiot|jerk" />
     </properties>
 </rule>
 <rule ref="category/java/documentation.xml/CommentRequired">
  <priority>1</priority>
     <properties>
         <property name="methodWithOverrideCommentRequirement" value="Ignored" />
         <property name="accessorCommentRequirement" value="Ignored" />
         <property name="headerCommentRequirement" value="Required" />
         <property name="fieldCommentRequirement" value="Ignored" />
         <property name="publicMethodCommentRequirement" value="Required" />
         <property name="protectedMethodCommentRequirement" value="Required" />
         <property name="enumCommentRequirement" value="Required" />
         <property name="serialVersionUIDCommentRequired" value="Ignored" />
     </properties>
 </rule>
 <rule ref="category/java/documentation.xml/CommentSize">
  <priority>4</priority>
     <properties>
         <property name="maxLines" value="25" />
         <property name="maxLineLength" value="150" />
     </properties>
 </rule>
 <rule ref="category/java/documentation.xml/UncommentedEmptyConstructor">
  <priority>1</priority>
  <properties>
         <property name="ignoreExplicitConstructorInvocation" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/documentation.xml/UncommentedEmptyMethodBody">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/security.xml/HardCodedCryptoKey">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/security.xml/InsecureCryptoIv">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/multithreading.xml/AvoidSynchronizedAtMethodLevel">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/multithreading.xml/AvoidThreadGroup">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/multithreading.xml/AvoidUsingVolatile">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/multithreading.xml/DoNotUseThreads">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/multithreading.xml/DontCallThreadRun">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/multithreading.xml/DoubleCheckedLocking">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/multithreading.xml/NonThreadSafeSingleton">
  <priority>1</priority>
  <properties>
         <property name="checkNonStaticMethods" value="true" />
         <property name="checkNonStaticFields" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/multithreading.xml/UnsynchronizedStaticFormatter">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/multithreading.xml/UseConcurrentHashMap">
  <priority>3</priority>
 </rule>
  <rule ref="category/java/multithreading.xml/UseNotifyAllInsteadOfNotify">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AssignmentInOperand">
  <priority>4</priority>
  <properties>
         <property name="allowIf" value="false" />
         <property name="allowFor" value="false" />
         <property name="allowWhile" value="false" />
         <property name="allowIncrementDecrement" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/errorprone.xml/AssignmentToNonFinalStatic">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidAccessibilityAlteration">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidAssertAsIdentifier">
  <priority>1</priority>
 </rule>
    <rule ref="category/java/errorprone.xml/AvoidBranchingStatementAsLastInLoop">
  <priority>1</priority>
  <properties>
          <property name="checkBreakLoopTypes" value="for|do|while" />
          <property name="checkContinueLoopTypes" value="for|do|while" />
          <property name="checkReturnLoopTypes" value="for|do|while" />
       </properties>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidCallingFinalize">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidCatchingNPE">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidCatchingThrowable">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidDecimalLiteralsInBigDecimalConstructor">
     <![CDATA[
      One might assume that the result of "new BigDecimal(0.1)" is exactly equal to 0.1, 
      but it is actually equal to .1000000000000000055511151231257827021181583404541015625. 
      This is because 0.1 cannot be represented exactly as a double (or as a binary fraction of any finite length). 
      Thus, the long value that is being passed in to the constructor is not exactly equal to 0.1, appearances notwithstanding.
      The (String) constructor, on the other hand, is perfectly predictable: ‘new BigDecimal("0.1")’ is exactly equal to 0.1,
      as one would expect. Therefore, it is generally recommended that the (String) constructor be used in preference to this one.
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidDuplicateLiterals">
  <priority>1</priority>
  <properties>
   <property name="separator" value="," />
         <property name="maxDuplicateLiterals" value="4" />
         <property name="minimumLength" value="3" />
         <property name="skipAnnotations" value="true" />
         <property name="exceptionList" value="" />
  </properties>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidEnumAsIdentifier">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/MethodWithSameNameAsEnclosingClass">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/SuspiciousHashcodeMethodName">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidFieldNameMatchingTypeName">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidFieldNameMatchingMethodName">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidInstanceofChecksInCatchClause">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidLiteralsInIfCondition">
  <priority>2</priority>
     <properties>
         <property name="ignoreMagicNumbers" value="-1,0" />
     </properties>
 </rule>
 <rule ref="category/java/errorprone.xml">
    <exclude name="DataflowAnomalyAnalysis" />
 </rule>
 <rule ref="category/java/errorprone.xml/MisplacedNullCheck">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidLosingExceptionInformation">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidMultipleUnaryOperators">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/AvoidUsingOctalValues">
  <priority>3</priority>
  <properties>
         <property name="strict" value="false" />
     </properties>
 </rule>
 <rule ref="category/java/errorprone.xml/ClassCastExceptionWithToArray">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/BrokenNullCheck">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/BadComparison">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/BeanMembersShouldSerialize">
  <priority>3</priority>
  <properties>
         <property name="ignoredAnnotations" value="lombok.Data|lombok.Getter|lombok.Value" />
         <property name="prefix" value="" />
     </properties>
 </rule>
 <rule ref="category/java/errorprone.xml/CallSuperFirst">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/CallSuperLast">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/CloneMethodMustBePublic">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/CloneMethodMustImplementCloneable">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/CloneMethodReturnTypeMustMatchClassName">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/ProperCloneImplementation">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/CloneThrowsCloneNotSupportedException">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/CloseResource">
  <priority>1</priority>
  <properties>
         <property name="closeTargets" value="" />
         <property name="types" value="java.lang.AutoCloseable,java.sql.Connection,java.sql.Statement,java.sql.ResultSet" />
         <property name="closeAsDefaultTarget" value="true" />
         <!-- Configure allowed types when using PMD 6.16.0 -->
         <!-- <property name="allowedResourceTypes" value="java.io.ByteArrayOutputStream|java.io.ByteArrayInputStream|java.io.StringWriter|java.io.CharArrayWriter|java.util.stream.Stream" /> -->
     </properties>
 </rule>
 <rule ref="category/java/errorprone.xml/CompareObjectsWithEquals">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/ConstructorCallsOverridableMethod">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/DetachedTestCase">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/DoNotCallGarbageCollectionExplicitly">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/DoNotCallSystemExit">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/DoNotExtendJavaLangThrowable">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/DoNotHardCodeSDCard">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/DoNotThrowExceptionInFinally">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/DontImportSun">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/DontUseFloatTypeForLoopIndices">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyCatchBlock">
  <priority>1</priority>
  <properties>
         <property name="allowCommentedBlocks" value="false" />
         <property name="allowExceptionNameRegex" value="^(ignored|expected)$" />
     </properties>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyFinalizer">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyFinallyBlock">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyIfStmt">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyWhileStmt">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyTryBlock">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptySwitchStatements">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptySynchronizedBlock">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyInitializer">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyStatementNotInLoop">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyInitializer">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EmptyStatementBlock">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/EqualsNull">
  <priority>1</priority>
 </rule>
    <rule ref="category/java/errorprone.xml/FinalizeDoesNotCallSuperFinalize">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/FinalizeOnlyCallsSuperFinalize">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/FinalizeOverloaded">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/FinalizeShouldBeProtected">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/IdempotentOperations">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/ImportFromSamePackage">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/InstantiationToGetClass">
  <priority>1</priority>
 </rule>
 <!-- Configure this rule when using PMD 6.19.0 -->
 <!-- <rule ref="category/java/errorprone.xml/InvalidLogMessageFormat">
  <priority>1</priority>
 </rule> -->
 <rule ref="category/java/errorprone.xml/JumbledIncrementer">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/JUnitSpelling">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/JUnitStaticSuite">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/ProperLogger">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/MissingBreakInSwitch">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/MissingSerialVersionUID">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/MissingStaticMethodInNonInstantiatableClass">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/MoreThanOneLogger">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/NonCaseLabelInSwitchStatement">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/NonStaticInitializer">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/NullAssignment">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/OverrideBothEqualsAndHashcode">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/ReturnEmptyArrayRatherThanNull">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/ReturnFromFinallyBlock">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/SimpleDateFormatNeedsLocale">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/SingleMethodSingleton">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/SingletonClassReturningNewInstance">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/StaticEJBFieldShouldBeFinal">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/StringBufferInstantiationWithChar">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/SuspiciousEqualsMethodName">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/SuspiciousOctalEscape">
  <priority>4</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/TestClassWithoutTestCases">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UnconditionalIfStatement">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UnnecessaryBooleanAssertion">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UnnecessaryCaseChange">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UnnecessaryConversionTemporary">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UnusedNullCheckInEquals">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UseCorrectExceptionLogging">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UseEqualsToCompareStrings">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UselessOperationOnImmutable">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UseLocaleWithCaseConversions">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/UseProperClassLoader">
  <![CDATA[
    In J2EE, the getClassLoader() method might not work as expected. 
    Use Thread.currentThread().getContextClassLoader() instead.
  ]]>
  <priority>3</priority>
 </rule>
 <rule ref="category/java/errorprone.xml/CheckSkipResult">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/performance.xml/AddEmptyString">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/AppendCharacterWithChar">
  <priority>3</priority>
 </rule>
 <rule ref="category/java/performance.xml/AvoidArrayLoops">
  <priority>2</priority>
 </rule>
 <rule ref="category/java/performance.xml/AvoidFileStream">
  <![CDATA[
    The FileInputStream and FileOutputStream classes contains a finalizer method which will cause garbage collection pauses. 
    See JDK-8080225 for details. The FileReader and FileWriter constructors instantiate FileInputStream and FileOutputStream, 
    again causing garbage collection issues while finalizer methods are called.
   -Use Files.newInputStream(Paths.get(fileName)) instead of new FileInputStream(fileName).
   -Use Files.newOutputStream(Paths.get(fileName)) instead of new FileOutputStream(fileName).
   -Use Files.newBufferedReader(Paths.get(fileName)) instead of new FileReader(fileName).
   -Use Files.newBufferedWriter(Paths.get(fileName)) instead of new FileWriter(fileName).
     Please note, that the java.nio API does not throw a FileNotFoundException anymore, 
     instead it throws a NoSuchFileException. If your code dealt explicitly with a FileNotFoundException, 
     then this needs to be adjusted. Both exceptions are subclasses of IOException, so catching that one covers both.
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/AvoidInstantiatingObjectsInLoops">
        <![CDATA[
      for (int i = 0; i < 10; i++) {
             Foo f = new Foo(); // Avoid this whenever you can it's really expensive
         }
  ]]>
  <priority>3</priority>
 </rule>
 <rule ref="category/java/performance.xml/AvoidUsingShortType">
  <![CDATA[
   Java uses the ‘short’ type to reduce memory usage, not to optimize calculation. 
   In fact, the JVM does not have any arithmetic capabilities for the short type: the JVM must convert the short into an int,
   do the proper calculation and convert the int back to a short. 
   Thus any storage gains found through use of the ‘short’ type may be offset by adverse impacts on performance.
   ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/BigIntegerInstantiation">
  <![CDATA[
   Don’t create instances of already existing BigInteger (BigInteger.ZERO, BigInteger.ONE) and for Java 1.5 onwards,
   BigInteger.TEN and BigDecimal (BigDecimal.ZERO, BigDecimal.ONE, BigDecimal.TEN)
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/BooleanInstantiation">
  <![CDATA[
   Avoid instantiating Boolean objects; you can reference Boolean.TRUE, Boolean.FALSE, or call Boolean.valueOf() instead.
   Note that new Boolean() is deprecated since JDK 9 for that reason.
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/IntegerInstantiation">
  <![CDATA[
   Calling new Integer() causes memory allocation that can be avoided by the static Integer.valueOf(). 
   It makes use of an internal cache that recycles earlier instances making it more memory efficient. 
   Note that new Integer() is deprecated since JDK 9 for that reason.
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/ByteInstantiation">
  <![CDATA[
   Calling new Byte() causes memory allocation that can be avoided by the static Byte.valueOf(). 
   It makes use of an internal cache that recycles earlier instances making it more memory efficient. 
   Note that new Byte() is deprecated since JDK 9 for that reason.
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/ShortInstantiation">
  <![CDATA[
      Calling new Short() causes memory allocation that can be avoided by the static Short.valueOf(). 
      It makes use of an internal cache that recycles earlier instances making it more memory efficient. 
      Note that new Short() is deprecated since JDK 9 for that reason.
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/LongInstantiation">
  <![CDATA[
      Calling new Long() causes memory allocation that can be avoided by the static Long.valueOf(). 
      It makes use of an internal cache that recycles earlier instances making it more memory efficient. 
      Note that new Long() is deprecated since JDK 9 for that reason.
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/SimplifyStartsWith">
  <![CDATA[
      boolean checkIt(String x) {
          return x.startsWith("a");   // suboptimal
      }
  
      boolean fasterCheckIt(String x) {
          return x.charAt(0) == 'a';  // faster approach
      }
  ]]>
  <priority>3</priority>
 </rule>
 <rule ref="category/java/performance.xml/UseStringBufferForStringAppends">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/UseArraysAsList">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/UnnecessaryWrapperObjectCreation">
  <![CDATA[
   public int convert(String s) {
       int i, i2;
   
       i = Integer.valueOf(s).intValue();  // this wastes an object
       i = Integer.parseInt(s);            // this is better
   
       i2 = Integer.valueOf(i).intValue(); // this wastes an object
       i2 = i;                             // this is better
   
       String s3 = Integer.valueOf(i2).toString(); // this wastes an object
       s3 = Integer.toString(i2);                  // this is better
   
       return i2;
   }
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/RedundantFieldInitializer">
  <![CDATA[
    public class C {
   // examples of redundant initializers
      boolean b   = false;    
      byte by     = 0;
      short s     = 0;
      char c      = 0;
      int i       = 0;
      long l      = 0;
      
      // examples of correct initializers
      boolean b1;    
      byte by1;
      short s1;
      char c1;
      int i1;
      long l1;
     }
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/OptimizableToArrayCall">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/TooFewBranchesForASwitchStatement">
  <priority>1</priority>
  <properties>
         <property name="minimumNumberCaseForASwitch" value="3" />
     </properties>
 </rule>
 <rule ref="category/java/performance.xml/StringInstantiation">
  <![CDATA[
   Avoid instantiating String objects; this is usually unnecessary since they are immutable and can be safely shared.
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/StringToString">
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/InefficientStringBuffering">
  <![CDATA[
   Avoid concatenating non-literals in a StringBuffer constructor or append() since intermediate buffers 
   will need to be be created and destroyed by the JVM.
   
   // Avoid this, two buffers are actually being created here
   StringBuffer sb = new StringBuffer("tmp = "+System.getProperty("java.io.tmpdir"));
   
   // do this instead
   StringBuffer sb = new StringBuffer("tmp = ");
   sb.append(System.getProperty("java.io.tmpdir"));
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/UseStringBufferLength">
  <![CDATA[
   Use StringBuffer.length() to determine StringBuffer length rather than using 
   StringBuffer.toString().equals("") or StringBuffer.toString().length() ==
   
   StringBuffer sb = new StringBuffer();
   if (sb.toString().equals("")) {}        // inefficient
   if (sb.length() == 0) {}                // preferred
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/ConsecutiveAppendsShouldReuse">
  <![CDATA[
   Consecutive calls to StringBuffer/StringBuilder .append should be chained, reusing the target object.
   This can improve the performance by producing a smaller bytecode, reducing overhead and improving inlining
   
   String foo = " ";
   StringBuffer buf = new StringBuffer();
   buf.append("Hello"); // poor
   buf.append(foo);
   buf.append("World");
   
   StringBuffer buf = new StringBuffer();
   buf.append("Hello").append(foo).append("World"); // good
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/ConsecutiveLiteralAppends">
  <![CDATA[
   Consecutively calling StringBuffer/StringBuilder.append(…) with literals should be avoided. 
   Since the literals are constants, they can already be combined into a single String literal and 
   this String can be appended in a single method call.
   
   StringBuffer buf = new StringBuffer();
   buf.append('h').append('e').append('l').append('l').append('o'); // poor
   buf.append("hello");                                             // good
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/UseIndexOfChar">
  <![CDATA[
   Use String.indexOf(char) when checking for the index of a single character; it executes faster.
   String s = "hello world";
   // avoid this
   if (s.indexOf("d") {}
   // instead do this
   if (s.indexOf('d') {}
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/InefficientEmptyStringCheck">
  <![CDATA[
   String.trim().length() == 0 (or String.trim().isEmpty() for the same reason) is an inefficient way to check 
   if a String is really blank, as it creates a new String object just to check its size.
   onsider creating a static function that loops through a string, checking Character.isWhitespace() 
   on each character and returning false if a non-whitespace character is found. 
   You can refer to Apache’s StringUtils#isBlank (in commons-lang), 
   Spring’s StringUtils#hasText (in the Spring framework) or 
   Google’s CharMatcher#whitespace (in Guava) for existing implementations 
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/InsufficientStringBufferDeclaration">
  <![CDATA[
   Failing to pre-size a StringBuffer or StringBuilder properly could cause it to re-size many times during runtime.
   This rule attempts to determine the total number the characters that are actually passed into StringBuffer.append(), 
   but represents a best guess "worst case" scenario. An empty StringBuffer/StringBuilder constructor initializes the object
   to 16 characters. This default is assumed if the length of the constructor can not be determined.
   
   StringBuffer bad = new StringBuffer();
   bad.append("This is a long string that will exceed the default 16 characters");
   
   StringBuffer good = new StringBuffer(41);
   good.append("This is a long string, which is pre-sized");
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/UselessStringValueOf">
  <![CDATA[
   public String convert(int i) {
       String s;
       s = "a" + String.valueOf(i);    // not required
       s = "a" + i;                    // preferred approach
       return s;
   }
  ]]>
  <priority>1</priority>
 </rule>
 <rule ref="category/java/performance.xml/UseArrayListInsteadOfVector">
  <![CDATA[
   ArrayList is a much better Collection implementation than Vector if thread-safe operation is not required.
  ]]>
  <priority>2</priority>
 </rule>
</ruleset>

Configuring Checkstyle maven plug-in: 

Here we are configuring checkstyle into build lifecycle under 'package' phage. See <phase> element inside <executions>/<execution> element. The <plugins> element is configured under <build> element which means the plugin will be executed during build (life cycle) process.

To run checkstyle you can use following command: mvn checkstyle:checkstyle

If you want to run checkstyle and want the build to fail if violations are found, then you can use following command: mvn checkstyle:check

Refer this page for more details:

https://maven.apache.org/plugins/maven-checkstyle-plugin/examples/custom-checker-config.html

<!-- Checkstyle integration -->
<plugin>
 <groupId>org.apache.maven.plugins</groupId>
 <artifactId>maven-checkstyle-plugin</artifactId>
 <version>3.1.0</version>
 <executions>
  <execution>
   <id>checkstyle</id>
   <phase>package</phase>
   <goals>
    <goal>check</goal>
   </goals>
   <configuration>
    <!-- Fail build if violations found -->
    <failOnViolation>true</failOnViolation>
    <!-- External configuration file location -->
    <configLocation>${basedir}/checkstyle.xml</configLocation>
    <!-- Includes packages as per the given wild card config. -->
    <includes>com/**/*.java</includes>
    <!-- Excludes packages as per the given wild card config. -->
    <excludes>com/github/pojo/**/*.java,com/github/abhinavmishra14/**/*Test.java</excludes>
   </configuration>
  </execution>
 </executions>
</plugin>

Sample Checkstyle RuleSet as per version 3.1.0 (checkstyle.xml)

For more details on ruleset, visit: https://checkstyle.sourceforge.io/config.html

<!DOCTYPE module PUBLIC
    "-//Puppy Crawl//DTD Check Configuration 1.2//EN"
    "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">

<module name="Checker">
 <module name="TreeWalker">
  <module name="JavadocMethod" />
  <module name="JavadocType" />
  <module name="JavadocVariable">
   <property name="scope" value="private"/>
   <property name="excludeScope" value="protected"/>
  </module>
  <module name="JavadocStyle">
   <property name="checkFirstSentence" value="false"/>
  </module>
 </module>

 <module name="BeforeExecutionExclusionFileFilter">   <property name="fileNamePattern" value="package\-info\.java$"/> </module>
</module>

Configuring plugins for generating reports for PMD, FindBugs/SpotBugs and JUnit test:

When we use 'mvn site' command, it generate site for the project containing all the information of project such has dependencies used, plugins used, Unit test cases success/failure report, PMD report, FindBugs report etc.

To configure reporting we will put the above configurations under the <reporting> element inside pom.xml.

<reporting>
 <plugins>
  <!-- Latest version of site plugin for handling the project report -->
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-site-plugin</artifactId>
   <version>3.8.2</version>
  </plugin>

  <!-- Reporting plugin -->
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-project-info-reports-plugin</artifactId>
   <configuration>
    <argLine>-Xmx1024m</argLine>
   </configuration>
   <version>2.7</version>
  </plugin>

  <!-- To publish JUnit test results -->
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-surefire-report-plugin</artifactId>
   <version>3.0.0-M3</version>
  </plugin>

  <!-- Checkstyle plugin -->
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-checkstyle-plugin</artifactId>
   <version>3.1.0</version>
   <configuration>
    <failOnViolation>true</failOnViolation>
    <configLocation>${basedir}/checkstyle.xml</configLocation>
    <includes>com/**/*.java</includes>
    <!-- <excludes></excludes> -->
   </configuration>
  </plugin>

  <!-- JXR for PMD as supporting plugin -->
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-jxr-plugin</artifactId>
   <version>3.0.0</version>
  </plugin>

  <!-- PMD Plugin -->
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-pmd-plugin</artifactId>
   <version>3.12.0</version>
   <configuration>
    <includes>
     <include>com/**/*.java</include>
    </includes>
    <!-- <excludes>
       <exclude></exclude>
     </excludes> -->
    <outputDirectory>${project.reporting.outputDirectory}</outputDirectory>
    <targetDirectory>${project.build.directory}</targetDirectory>
    <rulesets>
     <ruleset>${basedir}/pmd_ruleset.xml</ruleset>
    </rulesets>
   </configuration>
  </plugin>

  <!-- Findbugs plugin -->
  <plugin>
   <groupId>org.codehaus.mojo</groupId>
   <artifactId>findbugs-maven-plugin</artifactId>
   <version>3.0.5</version>
   <configuration>
    <debug>false</debug>
    <effort>Min</effort>
    <threshold>High</threshold>
    <xmlOutput>true</xmlOutput>
    <xmlOutputDirectory>${project.reporting.outputDirectory}</xmlOutputDirectory>
    <failOnError>true</failOnError>
    <!-- Indicates to analyze only given java packages, We are allowing everything here. -->
    <!-- <onlyAnalyze>com.*</onlyAnalyze> -->
   </configuration>
  </plugin>

  <!-- Javadocs plugin -->
  <plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-javadoc-plugin</artifactId>
   <version>3.1.1</version>
  </plugin>

  <!-- Spotbugs plugin -->
  <plugin>
   <groupId>com.github.spotbugs</groupId>
   <artifactId>spotbugs-maven-plugin</artifactId>
   <version>3.1.12.2</version>
  </plugin>
</plugins>
</reporting>

Once you will run 'mvn install site', a site folder will be created inside /target/site. You can open the 'index.html' generated by 'site' goal. You will see reports something like this(see screen below):