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">

<!--
    This configuration file enforces rules for a modified version of the module's code standard at
    https://oss-generic.github.io/process/codingstandards/coding-standards-java.html
-->

<module name="Checker">

    <module name="FileTabCharacter">
        <!-- Checks that there are no tab characters in the file. -->
    </module>

    <module name="NewlineAtEndOfFile">
        <!-- Accept LF, CR or CRLF to accomodate devs who prefer different line endings -->
        <property name="lineSeparator" value="lf_cr_crlf"/>
    </module>

    <module name="RegexpSingleline">
        <!-- Checks that FIXME is not used in comments.  TODO is preferred. -->
        <property name="format" value="((//.*)|(\*.*))FIXME" />
        <property name="message" value='TODO is preferred to FIXME."' />
    </module>

    <module name="SuppressionFilter">
        <property name="file" value="${config_loc}/suppressions.xml"/>
    </module>


    <!-- All Java AST specific tests live under TreeWalker module. -->
    <module name="TreeWalker">

        <!-- Required for SuppressionCommentFilter to work -->
        <module name="FileContentsHolder"/>

        <!-- Required to allow exceptions in code style -->
        <module name="SuppressionCommentFilter">
            <property name="offCommentFormat" value="CHECKSTYLE.OFF\: ([\w\|]+)"/>
            <property name="onCommentFormat" value="CHECKSTYLE.ON\: ([\w\|]+)"/>
            <property name="checkFormat" value="$1"/>
        </module>

        <!--
        IMPORT CHECKS
        -->

        <!-- Checks the ordering of import statements follow the rules that the default Eclipse formatter uses.
        The order rule "STATIC###STANDARD_JAVA_PACKAGE###SPECIAL_IMPORTS###THIRD_PARTY_PACKAGE" consists of:
          1. STATIC: static imports
          2. STANDARD_JAVA_PACKAGE: standard java/javax imports
          3. SPECIAL_IMPORTS: defined as org imports
          4. THIRD_PARTY_PACKAGE: defined as com imports
        -->
        <module name="CustomImportOrder">
            <property name="customImportOrderRules"
                      value="STATIC###STANDARD_JAVA_PACKAGE###SPECIAL_IMPORTS###THIRD_PARTY_PACKAGE"/>
            <property name="specialImportsRegExp" value="^org\."/>
            <property name="thirdPartyPackageRegExp" value="^com\."/>
            <property name="sortImportsInGroupAlphabetically" value="true"/>
        </module>

        <!-- Checks for redundant import statements.
        An import statement is redundant if:
          * It is a duplicate of another import. This is, when a class is imported more than once.
          * The class non-statically imported is from the java.lang package, e.g. importing java.lang.String.
          * The class non-statically imported is from the same package as the current package.
        -->
        <module name="RedundantImport"/>

        <!-- Checks for unused import statements.
        An import statement is unused if:
          It's not referenced in the file.
        -->
        <module name="UnusedImports"/>

        <module name="AvoidStarImport"/>

        <!--
        NAMING CHECKS
        -->

        <!-- Validate abbreviations (consecutive capital letters) length in identifier name -->
        <module name="AbbreviationAsWordInName">
            <property name="ignoreFinal" value="false"/>
            <property name="allowedAbbreviationLength" value="1"/>
        </module>

        <module name="PackageName">
            <!-- Validates identifiers for package names against the supplied expression. -->
            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]{1,})*$"/>
            <property name="severity" value="warning"/>
        </module>

        <module name="TypeName">
            <!-- Validates static, final fields against the expression "^[A-Z][a-zA-Z0-9]*$". -->
            <metadata name="altname" value="TypeName"/>
            <property name="severity" value="warning"/>
        </module>

        <module name="ConstantName">
            <!-- Validates non-private, static, final fields against the expression "^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$". -->
            <metadata name="altname" value="ConstantName"/>
            <property name="applyToPrivate" value="false"/>
            <message key="name.invalidPattern"
                     value="Variable ''{0}'' should be in ALL_CAPS (if it is a constant) or be private (otherwise)."/>
            <property name="severity" value="warning"/>
        </module>

        <module name="StaticVariableName">
            <!-- Validates static, non-final fields against the supplied expression. -->
            <metadata name="altname" value="StaticVariableName"/>
            <property name="format" value="^[a-z][a-zA-Z0-9]*_?$"/>
            <property name="severity" value="warning"/>
        </module>

        <module name="MemberName">
            <!-- Validates non-static members against the supplied expression. -->
            <metadata name="altname" value="MemberName"/>
            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
            <property name="severity" value="warning"/>
        </module>

        <module name="MethodName">
            <!-- Validates identifiers for method names against the supplied expression. -->
            <metadata name="altname" value="MethodName"/>
            <property name="format" value="^[a-z][a-zA-Z0-9]*(_[a-z][a-zA-Z0-9]+){0,2}$"/>
        </module>

        <module name="ParameterName">
            <!-- Validates identifiers for method parameters against the expression "^[a-z][a-zA-Z0-9]*$". -->
            <property name="severity" value="warning"/>
        </module>

        <module name="LocalFinalVariableName">
            <!-- Validates identifiers for local final variables against the expression "^[a-z][a-zA-Z0-9]*$". -->
            <property name="severity" value="warning"/>
        </module>

        <module name="LocalVariableName">
            <!-- Validates identifiers for local variables against the expression "^[a-z][a-zA-Z0-9]*$". -->
            <property name="severity" value="warning"/>
        </module>


        <!--
        LENGTH and CODING CHECKS
        -->

        <!-- Checks that array type declarations follow Java Style
          Java style: public static void main(String[] args) // Allowed
          C style:    public static void main(String args[]) // Not allowed
        -->
        <module name="ArrayTypeStyle"/>

        <!-- Checks if a catch block is empty and does not contain any comments. -->
        <module name="EmptyCatchBlock"/>

        <module name="LineLength">
            <!-- Checks if a line is too long. -->
            <property name="max" value="120"/>
        </module>

        <module name="LeftCurly">
            <!-- Checks for placement of the left curly brace ('{'). -->
            <property name="severity" value="warning"/>
        </module>

        <module name="RightCurly">
            <!-- Checks right curlies on CATCH, ELSE, and TRY blocks are on
            the same line. e.g., the following example is fine:
            <pre>
              if {
                ...
              } else
            </pre>
            -->
            <!-- This next example is not fine:
            <pre>
              if {
                ...
              }
              else
            </pre>
            -->
            <property name="severity" value="warning"/>
        </module>

        <!-- Checks for braces around loop blocks -->
        <module name="NeedBraces">
            <!--
            if (true) return 1; // Not allowed
            if (true) { return 1; } // Not allowed
            else if {
              return 1; // else if should always be multi line
            }
            if (true)
              return 1; // Not allowed
            -->
            <property name="allowEmptyLoopBody" value="true"/>
        </module>

        <!-- Checks that each variable declaration is in its own statement and on its own line. -->
        <module name="MultipleVariableDeclarations"/>

        <module name="OneStatementPerLine"/>

        <!-- Checks that long constants are defined with an upper ell.-->
        <module name="UpperEll" />

        <module name="FallThrough">
            <!-- Warn about falling through to the next case statement.  Similar to
            javac -Xlint:fallthrough, but the check is suppressed if a single-line comment
            on the last non-blank line preceding the fallen-into case contains 'fall through' (or
            some other variants which we don't publicized to promote consistency).
            -->
            <property name="reliefPattern"
                      value="fall through|Fall through|fallthru|Fallthru|falls through|Falls through|fallthrough|Fallthrough|No break|NO break|no break|continue on"/>
        </module>

        <module name="MissingSwitchDefault"/>

        <!-- Checks that Class variables should never be declared public. -->
        <module name="VisibilityModifier">
            <property name="protectedAllowed" value="true"/>
            <property name="allowPublicFinalFields" value="true"/>
            <property name="ignoreAnnotationCanonicalNames" value="RegisterExtension, TempDir"/>
        </module>

        <!--
        ORDER CHECKS
        -->

        <!-- Checks that the order of at-clauses follows the tagOrder default property value order.
             @author, @version, @param, @return, @throws, @exception, @see, @since, @serial, @serialField, @serialData, @deprecated
        -->
        <module name="AtclauseOrder"/>

        <!-- Checks if the Class and Interface declarations is organized in this order
          1. Class (static) variables. Order: public, protected, package level (no access modifier), private.
          2. Instance variables. Order: public, protected, package level (no access modifier), private.
          3. Constructors
          4. Methods
        -->
        <module name ="DeclarationOrder"/>

        <module name="ModifierOrder">
            <!-- Warn if modifier order is inconsistent with JLS3 8.1.1, 8.3.1, and
                 8.4.3.  The prescribed order is:
                 public, protected, private, abstract, static, final, transient, volatile,
                 synchronized, native, strictfp
              -->
        </module>

        <module name="OverloadMethodsDeclarationOrder"/>

        <!--
        WHITESPACE CHECKS
        -->

        <!-- Checks that comments are indented relative to their position in the code -->
        <module name="CommentsIndentation"/>

        <module name="WhitespaceAround">
            <!-- Checks that various tokens are surrounded by whitespace.
                 This includes most binary operators and keywords followed
                 by regular or curly braces.
            -->
            <property name="tokens" value="ASSIGN, BAND, BAND_ASSIGN, BOR,
        BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN,
        EQUAL, GE, GT, LAND, LCURLY, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE,
        LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF, LITERAL_RETURN,
        LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS,
        MINUS_ASSIGN, MOD, MOD_ASSIGN, NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION,
        RCURLY, SL, SLIST, SL_ASSIGN, SR_ASSIGN, STAR, STAR_ASSIGN"/>
            <!-- Allow empty constructors e.g. MyClass() {} -->
            <property name="allowEmptyConstructors" value="true" />
            <!-- Allow empty methods e.g. void func() {} -->
            <property name="allowEmptyMethods" value="true" />
            <!-- Allow empty types e.g. class Foo {}, enum Foo {} -->
            <property name="allowEmptyTypes" value="true" />
            <!-- Allow empty loops e.g. for (int i = 1; i > 1; i++) {} -->
            <property name="allowEmptyLoops" value="true" />
            <!-- Allow empty lambdas e.g. () -> {} -->
            <property name="allowEmptyLambdas" value="true" />
        </module>

        <module name="WhitespaceAfter">
            <!-- Checks that commas, semicolons and typecasts are followed by whitespace. -->
            <property name="tokens" value="COMMA, SEMI, TYPECAST"/>
        </module>

        <module name="NoWhitespaceAfter">
            <!-- Checks that there is no whitespace after various unary operators. Linebreaks are allowed. -->
            <property name="tokens" value="BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS,
        UNARY_PLUS"/>
            <property name="allowLineBreaks" 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>

        <module name="OperatorWrap">
            <!-- Checks that the non-assignment type operator is at the next line in a line wrap.
                 This includes "?", ":", "==", "!=", "/", "+", "-", "*", "%", ">>", ">>>",
                 ">=", ">", "<<", "<=", "<", "^", "|", "||", "&", "&&", "instanceof",
                 "&" when used in a generic upper or lower bounds constraints,
                   e.g. <T extends Foo & Bar>
                 "::" when used as a reference to a method or constructor without arguments.
                   e.g. String::compareToIgnoreCase
            -->
            <property name="tokens" value="QUESTION, COLON, EQUAL, NOT_EQUAL, DIV, PLUS, MINUS, STAR, MOD, SR, BSR,
        GE, GT, SL, LE, LT, BXOR, BOR, LOR, BAND, LAND, LITERAL_INSTANCEOF, TYPE_EXTENSION_AND, METHOD_REF"/>
            <property name="option" value="nl"/>
        </module>
        <module name="OperatorWrap">
            <!-- Checks that the assignment type operator is at the previous end of line in a line wrap.
                 This includes "=", "/=", "+=", "-=", "*=", "%=", ">>=", ">>>=", "<<=", "^=", "&=".
            -->
            <property name="tokens" value="ASSIGN, DIV_ASSIGN, PLUS_ASSIGN, MINUS_ASSIGN, STAR_ASSIGN, MOD_ASSIGN,
        SR_ASSIGN, BSR_ASSIGN, SL_ASSIGN, BXOR_ASSIGN, BOR_ASSIGN, BAND_ASSIGN"/>
            <property name="option" value="eol"/>
        </module>

        <module name="SeparatorWrap">
            <!-- Checks that the ".", "@" is at the next line in a line wrap. -->
            <property name="tokens" value="DOT, AT"/>
            <property name="option" value="nl"/>
        </module>
        <module name="SeparatorWrap">
            <!-- Checks that the ",", "]", "[", "...", ";", "(" is at the previous end of line in a line wrap. -->
            <property name="tokens" value="COMMA, RBRACK, ARRAY_DECLARATOR, ELLIPSIS, SEMI, LPAREN"/>
            <property name="option" value="eol"/>
        </module>

        <module name="Indentation">
            <property name="caseIndent" value="0" />
        </module>

        <module name="NoWhitespaceBefore">
            <!-- Checks that there is no whitespace before various unary operators. Linebreaks are allowed. -->
            <property name="tokens" value="SEMI, DOT, POST_DEC, POST_INC"/>
            <property name="allowLineBreaks" value="true"/>
        </module>

        <module name="ParenPad">
            <!-- Checks that there is no whitespace before close parenthesis or after open parenthesis. -->
            <property name="severity" value="warning"/>
        </module>

        <!-- Checks that non-whitespace characters are separated by no more than one whitespace character.
             a = 1; // Allowed
             a  = 1; // Not allowed (more than one space before =)
        -->
        <module name="SingleSpaceSeparator">
            <!-- Validate whitespace surrounding comments as well.
                 a = 1; // Allowed (single space before start of comment)
                 a = 1; /* Allowed (single space before start of comment) */
                 /* Allowed (single space after end of comment) */ a = 1;
                 a = 1;  // Not allowed (more than one space before start of comment)
                 a = 1;  /* Not allowed (more than one space before start of comment) */
                 /* Not allowed (more than one space after end of comment) */  a = 1;
                 This doesn't validate whitespace within comments so a comment /* like  this */ is allowed.
            -->
            <property name="validateComments" value="true"/>
        </module>

        <!--
        JAVADOC CHECKS
        -->

        <!-- Checks that every class, enumeration and interface have a header comment. -->
        <module name="JavadocType">
            <property name="allowMissingParamTags" value="true"/>
        </module>

        <!-- Checks that every public method (excluding getters, setters and constructors) has a header comment. -->
        <module name="JavadocMethod">
            <!-- Checks public methods that have more than 1 line of code.
              Single line of code methods are often due to refactor for readability.
            -->
            <property name="minLineCount" value="1"/>
            <property name="allowedAnnotations" value="Override, Test, BeforeAll, BeforeEach, AfterAll, AfterEach, Subscribe"/>
            <property name="scope" value="public"/>
            <property name="allowUndeclaredRTE" value="true"/>
            <property name="allowThrowsTagsForSubclasses" value="true"/>
            <property name="allowMissingParamTags" value="true"/>
            <property name="allowMissingThrowsTags" value="true"/>
            <property name="allowMissingReturnTag" value="true"/>
            <property name="allowMissingPropertyJavadoc" value="true"/>
            <property name="ignoreMethodNamesRegex" value="(set.*|get.*)"/>
            <property name="tokens" value="METHOD_DEF, ANNOTATION_FIELD_DEF"/>
        </module>
        <!-- Checks that every non-trivial private method (excluding getters, setters and constructors) has a header comment. -->
        <module name="JavadocMethod">
            <!-- Checks private methods that have more than 3 lines of code.
              We define methods that have more than 3 lines of code as non-trivial.
            -->
            <property name="minLineCount" value="3"/>
            <property name="allowedAnnotations" value="Override, Test, BeforeAll, BeforeEach, AfterAll, AfterEach, Subscribe"/>
            <property name="scope" value="private"/>
            <property name="allowUndeclaredRTE" value="true"/>
            <property name="allowThrowsTagsForSubclasses" value="true"/>
            <property name="allowMissingParamTags" value="true"/>
            <property name="allowMissingThrowsTags" value="true"/>
            <property name="allowMissingReturnTag" value="true"/>
            <property name="allowMissingPropertyJavadoc" value="true"/>
            <property name="ignoreMethodNamesRegex" value="(set.*|get.*)"/>
            <property name="tokens" value="METHOD_DEF, ANNOTATION_FIELD_DEF"/>
        </module>

    </module>
</module>