check_style.xml

<?xml version="1.0"?>
 <!DOCTYPE module PUBLIC
   "-//Puppy Crawl//DTD Check Configuration 1.2//EN"
   "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">
<!--keep the file in project root although NetBeans 8.0.2 doesn't find it there and allow to add additional project files (don't skip a proper project structure in favour of IDE deficies)-->
<module name="Checker">
    <!-- Following interprets the header file as regular expressions. -->
    <!-- Due to the fact that checkstyle only seems to be able to (re)use text from a license file if no text stands before the header in the source code and the fact that variable text is used in the header (package name), use the `RegexpHeader` module to validate the headers -->
    <!--<module name="RegexpHeader">
        <property
            name="header"
            value="^/\*\n \* Permission is hereby granted, free of charge, to any person obtaining a copy\n \* of this software and associated documentation files \(the &quot;Software&quot;\), to deal\n \* in the Software without restriction, including without limitation the rights\n \* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell\n \* copies of the Software, and to permit persons to whom the Software is\n \* furnished to do so, subject to the following conditions:\n \*\n \* The above copyright notice and this permission notice shall be included in\n \* all copies or substantial portions of the Software.\n \*\n \* THE SOFTWARE IS PROVIDED &quot;AS IS&quot;, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR\n \* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,\n \* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE\n \* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER\n \* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,\n \* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE\n \* SOFTWARE.\n \*/\n"/>
        <property name="fileExtensions" value="java"/>
    </module>-->
        <!-- Header check has to be left out because of multiple copyleft protected contributions (e.g. `org.flexdock.demos.maximizing.SimpleInternalFrame`) and the ridiculous incapacity of `maven-checkstyle-plugin` to process different regex headers (see http://stackoverflow.com/questions/33266679/how-to-specify-an-optional-regex-group-with-a-newline-character-in-checkstyles for details) -->
    <!-- Checks that there are no tab characters ('\t') in the source code. -->
    <module name="FileTabCharacter">
        <!-- Report on each line in each file -->
        <property name="eachLine" value="true"/>
    </module>
    <module name="TreeWalker">
        <!-- No EOL should be placed before block start ('{') -->
        <module name="LeftCurly">
            <property name="option" value="eol"/>
            <property name="severity" value="error"/>
        </module>
        <!-- '}' rules -->
        <module name="RightCurly">
            <!-- '}' should be on the same line as a next statement -->
            <property name="option" value="same"/>
            <property name="severity" value="error"/>
        </module>
        <!-- Braces are mandatory around code blocks -->
        <module name="NeedBraces">
            <property name="severity" value="error"/>
        </module>
        <!-- Checks the Javadoc of a method or constructor. -->
        <module name="JavadocMethod">
            <property name="scope" value="public"/>
            <property name="severity" value="warning"/>
        </module>
        <!-- Checks Javadoc comments for class and interface definitions. -->
        <module name="JavadocType">
            <property name="scope" value="public"/>
            <property name="severity" value="warning"/>
        </module>
        <!-- Checks for Naming Conventions.              -->
        <!-- See http://checkstyle.sourceforge.net/config_naming.html -->
        <!-- Sun Naming Conventions -->
        <module name="ConstantName"/>
        <module name="LocalFinalVariableName"/>
        <module name="LocalVariableName"/>
        <module name="MemberName"/>
        <module name="MethodName"/>
        <module name="PackageName"/>
        <module name="ParameterName"/>
        <module name="StaticVariableName"/>
        <module name="TypeName"/>
        <!-- Checks correct indentation of Java Code. -->
        <module name="Indentation">
            <!-- how many spaces to use for new indentation level -->
            <property name="basicOffset" value="4" />
            <!-- how far brace should be indented when on next line -->
            <property name="braceAdjustment" value="0"/>
            <!-- how much to indent a case label -->
            <property name="caseIndent" value="4"/>
        </module>
        <!-- Specify method parameters code conventions -->
        <!--<module name="MethodParamPad">
             Whitespace is required after method name
            <property name="option" value="space" />
             Check only methods and constructors declarations
            <property name="tokens" value="METHOD_DEF, CTOR_DEF" />
        </module>  -->
        <!-- Checks the policy on the padding of parentheses; i.e. whether a space is required after a left parenthesis and before a
        right parenthesis, or such spaces are forbidden. -->
        <!--<module name="ParenPad">
            Whitespace required before ')' and after ')'
            <property name="option" value="space"/>
        </module>  -->
        <module name="Regexp">
            <property name="format" value="[ \t]+$"/>
            <property name="illegalPattern" value="true"/>
            <property name="message" value="Trailing whitespace"/>
        </module>
        <module name="UnusedImports"/>
    </module>
</module>