ruleset.xml

<?xml version="1.0"?>

<ruleset name="PMD HappyCoders Rules"
  xmlns="http://pmd.sourceforge.net/ruleset/2.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 https://pmd.sourceforge.io/ruleset_2_0_0.xsd">

  <description>PMD ruleset for HappyCoders.eu</description>

  <rule ref="category/java/bestpractices.xml">
    <exclude name="AvoidReassigningParameters"/>  <!-- In Java, this is OK, IMO -->
    <exclude name="SwitchStmtsShouldHaveDefault"/><!-- PMD doesn't recognize Java's new switch statements -->
    <exclude name="UseVarargs"/>                  <!-- PMD would suggest varargs wherever we pass an array to be sorted -->
  </rule>

  <rule ref="category/java/codestyle.xml">
    <exclude name="AtLeastOneConstructor"/>       <!-- No need for artificial default constructors -->
    <exclude name="CommentDefaultAccessModifier"/><!-- We don't comment why we make fields private, protected or public. So why should we comment on default access? -->
    <exclude name="ConfusingTernary"/>            <!-- Sometimes they make the code flow easier to follow -->
    <exclude name="LocalVariableCouldBeFinal"/>   <!-- My personal opinion: "final" on variables is noise -->
    <exclude name="MethodArgumentCouldBeFinal"/>  <!-- My personal opinion: "final" on arguments is noise -->
    <exclude name="OnlyOneReturn"/>               <!-- This rule might have made sense decades ago when methods where hundreds of lines long -->
    <exclude name="ShortClassName"/>              <!-- Wouldn't allow class names like "User" -->
    <exclude name="ShortMethodName"/>             <!-- Wouldn't allow method names like "of" -->
    <exclude name="ShortVariable"/>               <!-- This is usually a valid check; however, in the search algorithms, we often use variables "i" and "j"Wouldn't allow method names like "of" -->
    <exclude name="CallSuperInConstructor"/>      <!-- IMO, this would be noise -->
  </rule>

  <rule ref="category/java/codestyle.xml/ClassNamingConventions">
    <properties>
      <property name="utilityClassPattern" value="[A-Z][a-zA-Z0-9]*" /><!-- Don't enforce specific names on utility classes! -->
    </properties>
  </rule>

  <rule ref="category/java/codestyle.xml/LongVariable">
    <properties>
      <property name="minimum" value="41" />      <!-- Default max is 16, which is not always enough -->
    </properties>
  </rule>

  <rule ref="category/java/design.xml">
    <exclude name="LawOfDemeter"/>                <!-- We don't want to apply this law -->
    <exclude name="CognitiveComplexity"/>         <!-- This is usually a valid check; however, search algorithms *are* complex (we could make the code easier by extracting several methods, but I prefer to have it as close to the actual algorithm description as possible) -->
    <exclude name="CyclomaticComplexity"/>        <!-- This is usually a valid check; however, search algorithms *are* complex (we could make the code easier by extracting several methods, but I prefer to have it as close to the actual algorithm description as possible) -->
    <exclude name="NPathComplexity"/>             <!-- This is usually a valid check; however, search algorithms *are* complex (we could make the code easier by extracting several methods, but I prefer to have it as close to the actual algorithm description as possible) -->
  </rule>

  <rule ref="category/java/documentation.xml">
    <exclude name="CommentRequired"/>             <!-- Don't need comments on *all* fields -->
    <exclude name="CommentSize"/>                 <!-- Don't limit the size of comments -->
  </rule>

  <rule ref="category/java/errorprone.xml">
    <exclude name="BeanMembersShouldSerialize"/>  <!-- We don't want to serialize anything -->
  </rule>

  <rule ref="category/java/errorprone.xml/AvoidLiteralsInIfCondition">
    <properties>
      <property name="ignoreMagicNumbers" value="-1,0,1,2" /><!-- Default is only -1 and 0; add 1, 2 -->
    </properties>
  </rule>

  <rule ref="category/java/multithreading.xml">
    <exclude name="DoNotUseThreads"/>             <!-- This warning is for Java EE applications -->
  </rule>

  <rule ref="category/java/performance.xml"/>

  <rule ref="category/java/security.xml"/>

</ruleset>