checkstyle.xml

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

<!--
  Checkstyle Configuration for Nop Platform
  Code quality check rules based on project coding standards
-->
<module name="Checker">

    <!-- Property definitions -->
    <property name="charset" value="UTF-8"/>
    <property name="severity" value="warning"/>
    <property name="fileExtensions" value="java, properties, xml"/>

       <!-- Empty block checks -->
    <module name="EmptyBlock">
        <property name="option" value="text"/>
    </module>

    <!-- Code block checks -->
    <module name="LeftCurly">
        <property name="option" value="eol"/>
        <message key="line.previous" value="'{' should be at the end of the line"/>
    </module>

    <module name="RightCurly">
        <property name="option" value="alone"/>
        <message key="line.alone" value="'}' should be alone on a line"/>
    </module>

    <module name="NeedBraces">
        <property name="allowSingleLineStatement" value="false"/>
        <property name="allowEmptyLoopBody" value="false"/>
        <property name="tokens" value="LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO"/>
    </module>

   
    <!-- Naming convention checks -->
    <module name="Naming">
        <!-- Class names: PascalCase -->
        <module name="TypeName">
            <property name="format" value="^[A-Z][a-zA-Z0-9]*$"/>
            <message key="name.invalidPattern" value="Class name ''{0}'' should follow PascalCase format"/>
        </module>

        <!-- Method names: camelCase -->
        <module name="MethodName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
            <message key="name.invalidPattern" value="Method name ''{0}'' should follow camelCase format"/>
        </module>

        <!-- Variable names: camelCase -->
        <module name="LocalVariableName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
            <message key="name.invalidPattern" value="Variable name ''{0}'' should follow camelCase format"/>
        </module>

        <!-- Constant names: UPPER_SNAKE_CASE -->
        <module name="ConstantName">
            <property name="format" value="^[A-Z][A-Z0-9_]*$"/>
            <message key="name.invalidPattern" value="Constant name ''{0}'' should follow UPPER_SNAKE_CASE format"/>
        </module>

        <!-- Parameter names: camelCase -->
        <module name="ParameterName">
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
            <message key="name.invalidPattern" value="Parameter name ''{0}'' should follow camelCase format"/>
        </module>
    </module>

    <!-- Import checks -->
    <module name="UnusedImports"/>
    <module name="RedundantImport"/>
    <module name="AvoidStarImport">
        <message key="import.avoidStar" value="Avoid using star import statements"/>
    </module>

    <module name="MissingDeprecated">
        <property name="skipJavadoc" value="false"/>
    </module>

    <!-- Code complexity checks -->
    <module name="CyclomaticComplexity">
        <property name="max" value="10"/>
        <property name="switchMax" value="10"/>
        <message key="cyclomaticComplexity" value="Cyclomatic complexity is {0}, recommended maximum is 10"/>
    </module>

    <module name="JavaNCSS">
        <property name="methodMaximum" value="50"/>
        <property name="classMaximum" value="500"/>
        <message key="ncs.method" value="Method non-commented source statement count is {0}, recommended maximum is 50"/>
    </module>

    <!-- Code duplication checks -->
    <module name="RegexpSingleline">
        <property name="format" value="System\.out\.println"/>
        <property name="message" value="Please use SLF4J logging framework instead of System.out.println"/>
    </module>

    <module name="RegexpSingleline">
        <property name="format" value="System\.err\.println"/>
        <property name="message" value="Please use SLF4J logging framework instead of System.err.println"/>
    </module>

    <!-- Equals and hashCode checks -->
    <module name="CovariantEquals"/>

    <!-- Finalizer checks -->
    <module name="NoFinalizer"/>

    <!-- Magic numbers and strings checks -->
    <module name="MagicNumber">
        <property name="ignoreNumbers" value="-1, 0, 1, 2"/>
        <property name="ignoreHashCodeMethod" value="true"/>
        <property name="ignoreEqualsMethod" value="true"/>
        <message key="magic.number" value="Please define a constant for number {0}"/>
    </module>

    <module name="StringLiteralEquality">
        <message key="string.literal.equality" value="String comparison should use equals() method instead of =="/>
    </module>

    <!-- Exception handling checks -->
    <module name="EmptyCatch">
        <property name="exceptionVariableName" value="expected"/>
        <message key="catch.block.empty" value="Catch block should not be empty"/>
    </module>

    <module name="IllegalThrows">
        <property name="illegalClassNames" value="java.lang.Error, java.lang.RuntimeException, java.lang.Throwable, java.lang.Exception"/>
        <message key="illegal.throws" value="Do not throw {0}, throw more specific exceptions"/>
    </module>

    <module name="IllegalToken">
        <property name="tokens" value="LITERAL_NATIVE"/>
        <message key="illegal.token" value="Do not use native method"/>
    </module>


    <!-- Size checks -->
    <module name="MethodLength">
        <property name="max" value="150"/>
        <property name="countEmpty" value="false"/>
        <message key="maxLen.method" value="Method length is {0} lines, recommended maximum is 150 lines"/>
    </module>

    <module name="ParameterNumber">
        <property name="max" value="7"/>
        <message key="maxParam" value="Parameter count is {0}, recommended maximum is 7 parameters"/>
    </module>

    <module name="AnonInnerLength">
        <property name="max" value="20"/>
        <message key="maxLen.anonInner" value="Anonymous inner class length is {0} lines, recommended maximum is 20 lines"/>
    </module>

</module>