checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
          "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
          "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">

<!-- the checks in this file are based off the Google Style Guide for Java -->
<!-- See https://google.github.io/styleguide/javaguide.html -->
<module name = "Checker">
    <!--======
    = ERRORS =
    =======-->
    <property name="charset" value="UTF-8"/>

    <module name="TreeWalker">
        <!--================================================
                            Class Design
        http://checkstyle.sourceforge.net/config_design.html
        =================================================-->

        <!-- Checks that each top-level class, interface or enum resides in a source file of its own.
             See http://checkstyle.sourceforge.net/config_design.html#OneTopLevelClass -->
        <module name="OneTopLevelClass"/>

        <!--==============================================
                           Miscellaneous
        http://checkstyle.sourceforge.net/config_misc.html
        ===============================================-->

        <!-- Checks that the outer type name and the file name match. For example, the class Foo must be in a file named Foo.java.
             See http://checkstyle.sourceforge.net/config_misc.html#OuterTypeFilename -->
        <module name="OuterTypeFilename"/>
    </module>

    <!--========
    = WARNINGS =
    =========-->

    <module name="TreeWalker">
        <property name="severity" value="warning"/>

        <!--====================================================
                              Annotations
        http://checkstyle.sourceforge.net/config_annotation.html
        =====================================================-->

        <!-- Check location of annotation on language elements.
             See http://checkstyle.sourceforge.net/config_annotation.html#AnnotationLocation -->
        <module name="AnnotationLocation">
            <property name="tokens" value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF"/>
        </module>
        <module name="AnnotationLocation">
            <property name="tokens" value="VARIABLE_DEF"/>
            <property name="allowSamelineMultipleAnnotations" value="true"/>
        </module>

        <!--================================================
                               Blocks
        http://checkstyle.sourceforge.net/config_blocks.html
        =================================================-->

        <!-- Checks for empty blocks.
             See http://checkstyle.sourceforge.net/config_blocks.html#EmptyBlock -->
        <module name="EmptyBlock">
            <property name="option" value="TEXT"/>
            <property name="tokens" value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH"/>
        </module>

        <!--================================================
                              Coding
        http://checkstyle.sourceforge.net/config_coding.html
        =================================================-->

        <!-- Checks for illegal token text.
             See http://checkstyle.sourceforge.net/config_coding.html#IllegalTokenText -->
        <module name="IllegalTokenText">
            <property name="tokens" value="STRING_LITERAL, CHAR_LITERAL"/>
            <property name="format" value="\\u00(08|09|0(a|A)|0(c|C)|0(d|D)|22|27|5(C|c))|\\(0(10|11|12|14|15|42|47)|134)"/>
            <property name="message" value="Avoid using corresponding octal or Unicode escape."/>
        </module>

        <!-- Checks for fall-through in switch statements. Finds locations where a case lacks a break, return, throw or continue statement.
             See http://checkstyle.sourceforge.net/config_coding.html#FallThrough -->
        <module name="FallThrough"/>

        <!-- Checks that switch statement has a "default" clause.
             See http://checkstyle.sourceforge.net/config_coding.html#MissingSwitchDefault -->
        <module name="MissingSwitchDefault"/>

        <!-- Verifies there are no finalize() methods defined in a class.
             See http://checkstyle.sourceforge.net/config_coding.html#NoFinalizer -->
        <module name="NoFinalizer"/>

        <!--=================================================
                              JavaDoc
        http://checkstyle.sourceforge.net/config_javadoc.html
        ==================================================-->

        <!-- Checks the order of at-clauses.
             See http://checkstyle.sourceforge.net/config_javadoc.html#AtclauseOrder -->
        <module name="AtclauseOrder">
            <property name="tagOrder" value="@param, @return, @throws, @deprecated"/>
            <property name="target" value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF, VARIABLE_DEF"/>
        </module>

        <!-- Checks the indentation of the continuation lines in at-clauses.
             See http://checkstyle.sourceforge.net/config_javadoc.html#JavadocTagContinuationIndentation -->
        <module name="JavadocTagContinuationIndentation"/>

        <!--==============================================
                           Miscellaneous
        http://checkstyle.sourceforge.net/config_misc.html
        ===============================================-->

        <!-- Restrict using Unicode escapes (e.g. \u221e).
             See http://checkstyle.sourceforge.net/config_misc.html#AvoidEscapedUnicodeCharacters -->
        <module name="AvoidEscapedUnicodeCharacters">
            <property name="allowEscapesForControlCharacters" value="true"/>
            <property name="allowByTailComment" value="true"/>
            <property name="allowNonPrintableEscapes" value="true"/>
        </module>

        <!-- Checks the style of array type definitions.
             See http://checkstyle.sourceforge.net/config_misc.html#ArrayTypeStyle -->
        <module name="ArrayTypeStyle"/>

        <!-- Checks that long constants are defined with an upper ell.
             That is ' L' and not 'l'. The capital L looks a lot like 1.
             See http://checkstyle.sourceforge.net/config_misc.html#UpperEll -->
        <module name="UpperEll"/>

        <!--================================================
                          Naming Conventions
        http://checkstyle.sourceforge.net/config_naming.html
        =================================================-->

        <!-- The Check validate abbreviations (consecutive capital letters) length in identifier name, it also allows to enforce camel case naming.
             See http://checkstyle.sourceforge.net/config_naming.html#AbbreviationAsWordInName -->
		<!-- NOTE: differs from the Google style guide -->
        <module name="AbbreviationAsWordInName">
            <property name="ignoreFinal" value="true"/> <!-- changed from false -->
            <property name="allowedAbbreviations" value="JSON, LCOO"/> <!-- added -->
            <property name="allowedAbbreviationLength" value="3"/> <!-- changed from 1 -->
        </module>

        <!-- Validates identifiers for class type parameters.
             See http://checkstyle.sourceforge.net/config_naming.html#ClassTypeParameterName -->
        <module name="ClassTypeParameterName">
            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
            <message key="name.invalidPattern" value="Class type name ''{0}'' must match pattern ''{1}''."/>
        </module>

        <!-- Validates identifiers for interface type parameters.
             See http://checkstyle.sourceforge.net/config_naming.html#InterfaceTypeParameterName -->
        <module name="InterfaceTypeParameterName">
            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
            <message key="name.invalidPattern" value="Interface type name ''{0}'' must match pattern ''{1}''."/>
        </module>

        <!-- Validates identifiers for methods.
             See http://checkstyle.sourceforge.net/config_naming.html#MethodName -->
        <module name="MethodName">
            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9_]*$"/>
            <message key="name.invalidPattern" value="Method name ''{0}'' must match pattern ''{1}''."/>
        </module>

        <!-- Validates identifiers for method type parameters.
             See http://checkstyle.sourceforge.net/config_naming.html#MethodTypeParameterName -->
        <module name="MethodTypeParameterName">
            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
            <message key="name.invalidPattern" value="Method type name ''{0}'' must match pattern ''{1}''."/>
        </module>

        <!-- Validates identifiers for packages.
             See http://checkstyle.sourceforge.net/config_naming.html#PackageName -->
        <module name="PackageName">
            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
            <message key="name.invalidPattern" value="Package name ''{0}'' must match pattern ''{1}''."/>
        </module>

        <!-- Validates identifiers for types.
             See http://checkstyle.sourceforge.net/config_naming.html#TypeName -->
        <module name="TypeName">
            <message key="name.invalidPattern" value="Type name ''{0}'' must match pattern ''{1}''."/>
        </module>

        <!--====================================================
                               Whitespace
        http://checkstyle.sourceforge.net/config_whitespace.html
        =====================================================-->

        <!-- Checks that the whitespace around the Generic tokens (angle brackets) "<" and ">" are correct to the typical convention.
             See http://checkstyle.sourceforge.net/config_whitespace.html#GenericWhitespace -->
        <module name="GenericWhitespace">
            <message key="ws.followed" value="GenericWhitespace ''{0}'' is followed by whitespace."/>
            <message key="ws.preceded" value="GenericWhitespace ''{0}'' is preceded with whitespace."/>
            <message key="ws.illegalFollow" value="GenericWhitespace ''{0}'' should followed by whitespace."/>
            <message key="ws.notPreceded" value="GenericWhitespace ''{0}'' is not preceded with whitespace."/>
        </module>

        <!-- Checks that chosen statements are not line-wrapped.
             See http://checkstyle.sourceforge.net/config_whitespace.html#NoLineWrap -->
        <module name="NoLineWrap"/>

        <!-- Checks line wrapping with separators.
             See http://checkstyle.sourceforge.net/config_whitespace.html#SeparatorWrap -->
        <module name="SeparatorWrap">
            <property name="tokens" value="DOT"/>
            <property name="option" value="nl"/>
        </module>
        <module name="SeparatorWrap">
            <property name="tokens" value="COMMA"/>
            <property name="option" value="EOL"/>
        </module>
    </module>
</module>