checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC
        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
        "http://checkstyle.sourceforge.net/dtds/configuration_1_3.dtd">
<!--
DSpace CodeStyle Requirements

  1. 4-space indents for Java, and 2-space indents for XML. NO TABS ALLOWED.
  2. K&R style braces required. Braces required on all blocks.
  3. Do not use wildcard imports (e.g. import java.util.*). Duplicated or unused imports also not allowed.
  4. Javadocs should exist for all public classes and methods. (Methods rule is unenforced at this time.) Keep it short and to the point
  5. Maximum line length is 120 characters (except for long URLs, packages or imports)
  6. No trailing spaces allowed (except in comments)
  7. Tokens should be surrounded by whitespace (see http://checkstyle.sourceforge.net/config_whitespace.html#WhitespaceAround)
  8. Each source file must include our license header (validated separately by license-maven-plugin, see pom.xml)

For more information on CheckStyle configurations below, see: http://checkstyle.sourceforge.net/checks.html
-->
<module name="Checker">
    <!-- Configure checker to use UTF-8 encoding -->
    <property name="charset" value="UTF-8"/>
    <!-- Configure checker to run on files with these extensions -->
    <property name="fileExtensions" value="java, properties, cfg, xml"/>

    <!-- Suppression configurations in checkstyle-suppressions.xml in same directory -->
    <module name="SuppressionFilter">
        <property name="file" value="${checkstyle.suppressions.file}" default="checkstyle-suppressions.xml"/>
    </module>

    <!-- No tab characters ('\t') allowed in the source code -->
    <module name="FileTabCharacter">
        <property name="eachLine" value="true"/>
        <property name="fileExtensions" value="java, properties, cfg, css, js, xml"/>
    </module>

    <!-- No Trailing Whitespace, except on lines that only have an asterisk (e.g. Javadoc comments) -->
    <module name="RegexpSingleline">
        <property name="format" value="(?&lt;!\*)\s+$|\*\s\s+$"/>
        <property name="message" value="Line has trailing whitespace"/>
        <property name="fileExtensions" value="java, properties, cfg, css, js, xml"/>
    </module>

    <!-- Allow individual lines of code to be excluded from these rules, if they are annotated
         with @SuppressWarnings. See also SuppressWarningsHolder below -->
    <module name="SuppressWarningsFilter" />

    <!-- Maximum line length is 120 characters -->
    <module name="LineLength">
        <property name="fileExtensions" value="java"/>
        <property name="max" value="120"/>
        <!-- Only exceptions for packages, imports, URLs, and JavaDoc {@link} tags -->
        <property name="ignorePattern" value="^package.*|^import.*|http://|https://|@link"/>
    </module>

    <!-- Check individual Java source files for specific rules -->
    <module name="TreeWalker">
        <!-- Highlight any TODO or FIXME comments in info messages -->
        <module name="TodoComment">
            <property name="severity" value="info"/>
            <property name="format" value="(TODO)|(FIXME)"/>
        </module>

        <!-- Do not report errors on any lines annotated with @SuppressWarnings -->
        <module name="SuppressWarningsHolder"/>

        <!-- ##### Import statement requirements ##### -->
        <!-- Star imports (e.g. import java.util.*) are NOT ALLOWED -->
        <module name="AvoidStarImport"/>
        <!-- Redundant import statements are NOT ALLOWED -->
        <module name="RedundantImport"/>
        <!-- Unused import statements are NOT ALLOWED -->
        <module name="UnusedImports"/>
        <!-- Ensure imports appear alphabetically and grouped -->
        <module name="CustomImportOrder">
            <property name="sortImportsInGroupAlphabetically" value="true"/>
            <property name="separateLineBetweenGroups" value="true"/>
            <property name="customImportOrderRules" value="STATIC###STANDARD_JAVA_PACKAGE###THIRD_PARTY_PACKAGE"/>
        </module>

        <!-- ##### Javadocs requirements ##### -->
        <!-- Requirements for Javadocs for classes/interfaces -->
        <module name="JavadocType">
            <!-- All public classes/interfaces MUST HAVE Javadocs -->
            <property name="scope" value="public"/>
            <!-- Add an exception for anonymous inner classes -->
            <property name="excludeScope" value="anoninner"/>
            <!-- Ignore errors related to unknown tags -->
            <property name="allowUnknownTags" value="true"/>
            <!-- Allow params tags to be optional -->
            <property name="allowMissingParamTags" value="false"/>
        </module>
        <!-- Requirements for Javadocs for methods -->
        <module name="JavadocMethod">
            <!-- All public methods MUST HAVE Javadocs -->
            <property name="scope" value="public"/>
            <!-- Allow params, throws and return tags to be optional -->
            <property name="allowMissingParamTags" value="true"/>
            <property name="allowMissingReturnTag" value="true"/>
        </module>

        <!-- ##### Requirements for K&R Style braces ##### -->
        <!-- Code blocks MUST HAVE braces, even single line statements (if, while, etc) -->
        <module name="NeedBraces"/>
        <!-- Left braces should be at the end of current line (default value)-->
        <module name="LeftCurly"/>
        <!-- Right braces should be on start of a new line (default value) -->
        <module name="RightCurly"/>

        <!-- ##### Indentation / Whitespace requirements ##### -->
        <!-- Require 4-space indentation (default value) -->
        <module name="Indentation"/>
        <!-- Whitespace should exist around all major tokens -->
        <module name="WhitespaceAround">
            <!-- However, make an exception for empty constructors, methods, types, etc. -->
            <property name="allowEmptyConstructors" value="true"/>
            <property name="allowEmptyMethods" value="true"/>
            <property name="allowEmptyTypes" value="true"/>
            <property name="allowEmptyLoops" value="true"/>
        </module>
        <!-- Validate whitespace around Generics (angle brackets) per typical conventions
             http://checkstyle.sourceforge.net/config_whitespace.html#GenericWhitespace -->
        <module name="GenericWhitespace"/>

        <!-- ##### Requirements for "switch" statements ##### -->
        <!-- "switch" statements MUST have a "default" clause -->
        <module name="MissingSwitchDefault"/>
        <!-- "case" clauses in switch statements MUST include break, return, throw or continue -->
        <module name="FallThrough"/>

        <!-- ##### Other / Miscellaneous requirements ##### -->
        <!-- Require utility classes do not have a public constructor -->
        <module name="HideUtilityClassConstructor"/>
        <!-- Require each variable declaration is its own statement on its own line -->
        <module name="MultipleVariableDeclarations"/>
        <!-- Each line of code can only include one statement -->
        <module name="OneStatementPerLine"/>
        <!-- Require that "catch" statements are not empty (must at least contain a comment) -->
        <module name="EmptyCatchBlock"/>
    </module>
</module>