style.xml

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

<module name = "Checker">
    <property name="charset" value="UTF-8"/>

    <property name="severity" value="error"/>

    <property name="fileExtensions" value="java, properties, xml"/>

    <!-- Files end in a newline -->
    <module name="NewlineAtEndOfFile"/>

    <module name="TreeWalker">
        <property name="tabWidth" value="4"/>

        <!-- Lines are indented with tabs -->
        <module name="RegexpSinglelineJava">
            <property name="format" value="^\t* "/>
            <property name="message" value="Indent must use tabs, not spaces"/>
            <property name="ignoreComments" value="true"/>
        </module>

        <!-- The filename matches the class or type declared in the file  -->
        <module name="OuterTypeFilename"/>

        <!-- There is only one top-level cass per file  -->
        <module name="OneTopLevelClass"/>

        <!-- Imports and package declarations don't have linebreaks  -->
        <module name="NoLineWrap"/>

        <!-- No empty blocks for try/if/switch (not case/default) -->
        <module name="EmptyBlock">
            <property name="option" value="TEXT"/>
            <property name="tokens"
             value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH"/>
        </module>

        <!-- `if`s and loops have braces -->
        <module name="NeedBraces">
            <property name="allowSingleLineStatement" value="true"/>
            <property name="allowEmptyLoopBody" value="true"/>
        </module>

        <!-- `if (...) {`, not `if (...) \n {` -->
        <module name="LeftCurly"/>

        <!-- `} else`, not `} \n else` -->
        <module name="RightCurly">
            <property name="id" value="RightCurlySame"/>
            <property name="tokens" value="LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_DO"/>
        </module>
        <module name="RightCurly">
            <property name="id" value="RightCurlyAlone"/>
            <property name="option" value="alone"/>
            <property name="tokens" value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, STATIC_INIT, INSTANCE_INIT"/>
        </module>

        <!-- `a = b`, not `a=b`; `if (...)`, not `if(...)`; etc -->
        <module name="WhitespaceAround">
            <property name="allowEmptyConstructors" value="true"/>
            <property name="allowEmptyMethods" value="true"/>
            <property name="allowEmptyTypes" value="true"/>
            <property name="allowEmptyLoops" value="true"/>
            <property name="allowEmptyLambdas" value="true"/>
            <message key="ws.notFollowed"
             value="WhitespaceAround: ''{0}'' is not followed by whitespace."/>
            <message key="ws.notPreceded"
             value="WhitespaceAround: ''{0}'' is not preceded with whitespace."/>
        </module>

        <!-- One statement per line -->
        <module name="OneStatementPerLine"/>

        <!-- Java-style `int[] ar` rather than C-style `int ar[]` -->
        <module name="ArrayTypeStyle">
            <message key="array.type.style" value="Array brackets should follow the contained type: `int[] ar`, not `int ar[]`"/>
        </module>

        <!-- Switch statements should have a default, even if it's just `/* pass */` or `throw new Error("unreachable");`-->
        <module name="MissingSwitchDefault"/>

        <!-- Fallthrough in non-empty `case`s needs to be marked explicitly with a `// falls through` comment -->
        <module name="FallThrough"/>

        <!-- Long numeric literals are written `0L`, not `0l` -->
        <module name="UpperEll"/>

        <!-- Modifiers appear in the order recommended by the Java standard -->
        <module name="ModifierOrder">
            <message key="mod.order" value="Modifier order should be `public abstract static final synchronized` etc; see http://checkstyle.sourceforge.net/config_modifier.html#ModifierOrder"/>
        </module>

        <!-- There is a blank line between methods and in other similar places -->
        <module name="EmptyLineSeparator">
            <property name="allowNoEmptyLineBetweenFields" value="true"/>
            <property name="tokens" value="PACKAGE_DEF, IMPORT, STATIC_INIT, INSTANCE_INIT, METHOD_DEF, CTOR_DEF"/>
        </module>

        <!-- `a\n.b`, not `a.\nb` -->
        <module name="SeparatorWrap">
            <property name="id" value="SeparatorWrapDot"/>
            <property name="tokens" value="DOT"/>
            <property name="option" value="nl"/>
        </module>

        <!-- `f(a,\nb)`, not `f(a\n, b)` -->
        <module name="SeparatorWrap">
            <property name="id" value="SeparatorWrapComma"/>
            <property name="tokens" value="COMMA"/>
            <property name="option" value="EOL"/>
        </module>

        <!-- `a\n::b`, not `a::\nb` -->
        <module name="SeparatorWrap">
            <property name="id" value="SeparatorWrapMethodRef"/>
            <property name="tokens" value="METHOD_REF"/>
            <property name="option" value="nl"/>
        </module>

        <!-- Generics look like `<T> void f()` or `a.<T>b()`, not anything else -->
        <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>

        <!-- Indent by one tab -->
        <module name="Indentation">
            <property name="basicOffset" value="4"/>
            <property name="braceAdjustment" value="0"/>
            <property name="caseIndent" value="4"/>
            <property name="throwsIndent" value="4"/>
            <property name="lineWrappingIndentation" value="4"/>
            <property name="arrayInitIndent" value="4"/>
        </module>

        <!-- Overloaded methods are grouped together -->
        <module name="OverloadMethodsDeclarationOrder"/>

        <!-- `void f(int a)`, not `void f( int a )` -->
        <module name="MethodParamPad"/>

        <!-- No stray whitespace before semicolons, etc -->
        <module name="NoWhitespaceBefore">
            <property name="tokens"
             value="COMMA, SEMI, POST_INC, POST_DEC, DOT, ELLIPSIS, METHOD_REF"/>
            <property name="allowLineBreaks" value="true"/>
        </module>

        <!-- `(a + b)`, not `( a + b )` -->
        <module name="ParenPad"/>

        <!-- Comments are indented to the same depth as surrounding code -->
        <module name="CommentsIndentation"/>
    </module>
</module>