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">

<module name="Checker">

    <!-- no explicit TAB characters in source code -->
    <module name="FileTabCharacter"/>

    <module name="TreeWalker">
        <!-- Enforce standard Java field, class, method naming conventions -->
        <module name="ConstantName" />
        <module name="LocalFinalVariableName" />
        <module name="LocalVariableName" />
        <module name="MethodName" />
        <module name="MemberName" />
        <module name="TypeName" />
        <module name="StaticVariableName" />

        <!-- Don't allow most kinds of empty blocks -->
        <module name="EmptyBlock">
            <!-- empty blocks for catch and instance init are allowed -->
            <property name="tokens" value="LITERAL_DO,LITERAL_ELSE,LITERAL_FINALLY,LITERAL_IF,LITERAL_FOR,LITERAL_TRY,LITERAL_WHILE" />
        </module>

        <!-- Java Generic param decls do not require whitespace inside of angle brackets -->
        <module name="GenericWhitespace" />

        <!-- no whitespace just after enter or before exit parens block i.e. if (good != bad) { ... } -->
        <module name="ParenPad" />

        <!-- Use whitespace after paren-based typecase, semicolon, or comma unless at EOL -->
        <module name="WhitespaceAfter" />

        <!-- Use whitespace around typical tokens like = sign. Empty method/class decl should use { } and so on -->
        <module name="WhitespaceAround" />

        <!-- stmts that form blocks need to use curlies always (like if..else) -->
        <module name="NeedBraces" />

        <!-- anonymous non-static blocks inline should be avoided and are often cut/paste/debug errors -->
        <module name="AvoidNestedBlocks" />

        <!-- Utility classes w/all-static methods should not have public ctors -->
        <module name="HideUtilityClassConstructor" />

        <!-- defining an equals() method w/o Overriding Object#equals properly will give you master course in debugging -->
        <module name="CovariantEquals" />

        <!-- ALWAYS override Object#hashCode when you override Object#equals and vice versa -->
        <module name="EqualsHashCode" />

        <!-- Warn us when same-name declarations shadow decl's from the enclosing scope -->
        <module name="HiddenField">
            <property name="tokens" value="VARIABLE_DEF" />
            <property name="ignoreConstructorParameter" value="true" />
            <property name="ignoreSetter" value="true" />
        </module>

        <!-- Make sure all switch stmts have a matching default case at the end of the switch block -->
        <module name="MissingSwitchDefault" />
        <module name="DefaultComesLast" />

        <!-- make sure the index of a for loop is not modified inside that loop -->
        <module name="ModifiedControlVariable" />

        <!-- all Java string equality must be checked with Object#equals not == -->
        <module name="StringLiteralEquality" />

        <!-- Avoid nested for loops beyond depth 3, O(n^3) is shitty enough -->
        <module name="NestedForDepth">
            <property name="max" value="3" />
        </module>

        <!-- Don't every use/modify Object#clone its basically broken in Java -->
        <module name="NoClone" />

        <!-- if class overrides finalize() (better be good reason) then better call super.finalize() -->
        <module name="SuperFinalize" />

        <!-- Make sure every java class is declared in an associated package, you can't import top-level class decls -->
        <module name="PackageDeclaration" />

        <!-- one variable decl per line/stmt -->
        <module name="MultipleVariableDeclarations" />

        <!-- get rid of extra parens without risking pilot error -->
        <module name="UnnecessaryParentheses"/>

        <!-- one stmt per line -->
        <module name="OneStatementPerLine"/>

        <!-- no redundant import stmts -->
        <module name="RedundantImport"/>

        <!-- don't import classes that are never used in the code -->
        <module name="UnusedImports">
            <property name="processJavadoc" value="false" />
        </module>

        <!-- Java will do dumb stuff if you aren't explicit: 0 == int, 0L == long, 0l == confusing -->
        <module name="UpperEll"/>

        <!-- Outermost type declaration and Java file name must match -->
        <module name="OuterTypeFilename"/>

        <!-- Java interfaces always have public static final fields and public methods -->
        <module name="RedundantModifier"/>

    </module>

</module>