checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC
    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
    "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">

  <!-- Fail fast -->
  <property name="severity" value="error"/>

  <!-- File-level checks -->
  <module name="NewlineAtEndOfFile"/>
  <module name="FileTabCharacter"/>

  <!-- TreeWalker = Java AST rules -->
  <module name="TreeWalker">

    <!-- Enforce braces -->
    <module name="NeedBraces"/>

    <!-- Prevent accidental fallthrough -->
    <module name="FallThrough"/>

    <!-- Catch empty blocks -->
    <module name="EmptyBlock"/>

    <!-- Equals & hashCode correctness -->
    <module name="EqualsHashCode"/>

    <!-- Avoid == for object comparison -->
    <module name="EqualsAvoidNull"/>

    <!-- Control flow clarity -->
    <module name="AvoidNestedBlocks"/>
    <module name="MissingSwitchDefault"/>

    <!-- Common bug patterns -->
    <module name="IllegalCatch">
      <property name="illegalClassNames" value="java.lang.Throwable"/>
    </module>  <!-- forbids catch(Throwable, Exception) -->
    <module name="IllegalThrows"/>  <!-- forbids throws Throwable, Error -->

    <!-- Safer boolean logic -->
    <module name="SimplifyBooleanExpression"/>
    <module name="SimplifyBooleanReturn"/>

    <!-- Readability -->
    <module name="OneStatementPerLine"/>
    <module name="MultipleVariableDeclarations"/>

    <!-- Javadoc -->
    <!-- Require Javadoc comments to exist -->
    <module name="MissingJavadocType">
      <property name="scope" value="public"/>
      <property name="skipAnnotations" value="Generated"/>
    </module>

    <!-- Validate the content of existing Javadocs -->
    <module name="JavadocType">
      <property name="scope" value="public"/>
      <property name="allowMissingParamTags" value="false"/>
      <property name="allowUnknownTags" value="true"/>
    </module>

  </module>
</module>