checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
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The ASF licenses this file to You under the Apache License, Version 2.0
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     http://www.apache.org/licenses/LICENSE-2.0
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distributed under the License is distributed on an "AS IS" BASIS,
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limitations under the License.
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<!DOCTYPE module PUBLIC
  "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
  "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">

<!-- This is a checkstyle configuration file. For descriptions of what the 
	following rules do, please see the checkstyle configuration page at http://checkstyle.sourceforge.net/config.html -->

<module name="Checker">

  <module name="FileTabCharacter">
    <!-- Checks that there are no tab characters in the file. -->
  </module>

  <module name="NewlineAtEndOfFile">
    <property name="lineSeparator" value="lf"/>
  </module>

  <module name="RegexpSingleline">
    <!-- Checks that FIXME is not used in comments. TODO is preferred. -->
    <property name="format" value="((//.*)|(\*.*))FIXME"/>
    <property name="message"
      value='TODO is preferred to FIXME.  e.g. "TODO(johndoe): Refactor when v2 is released."'/>
  </module>

  <module name="RegexpSingleline">
    <!-- Checks that TODOs are named. (Actually, just that they are followed
      by an open paren.) -->
    <property name="format" value="((//.*)|(\*.*))TODO[^(]"/>
    <property name="message"
      value='All TODOs should be named.  e.g. "TODO(johndoe): Refactor when v2 is released."'/>
  </module>

  <!-- <module name="JavadocPackage"> - Checks that each Java package has
    a Javadoc file used for commenting. Only allows a package-info.java, not
    package.html. </module> -->
  <!-- All Java AST specific tests live under TreeWalker module. -->
  <module name="TreeWalker">

    <!-- IMPORT CHECKS -->

    <module name="RedundantImport">
      <!-- Checks for redundant import statements. -->
      <property name="severity" value="error"/>
    </module>
    <module name="ImportOrder">
      <property name="severity" value="warning"/>
      <property name="groups" value="com.google,junit,net,org,java,javax,*,org.apache.zeppelin"/>
      <property name="option" value="top"/>
      <property name="tokens" value="STATIC_IMPORT, IMPORT"/>
    </module>
    <!-- JAVADOC CHECKS -->

    <!-- Checks for Javadoc comments. -->
    <!-- See http://checkstyle.sf.net/config_javadoc.html -->
    <module name="JavadocMethod">
      <property name="scope" value="protected"/>
      <property name="severity" value="warning"/>
      <property name="allowMissingJavadoc" value="true"/>
      <property name="allowMissingParamTags" value="true"/>
      <property name="allowMissingReturnTag" value="true"/>
      <property name="allowMissingThrowsTags" value="true"/>
      <property name="allowThrowsTagsForSubclasses" value="true"/>
      <property name="allowUndeclaredRTE" value="true"/>
    </module>

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

    <!-- NAMING CHECKS -->

    <!-- Item 38 - Adhere to generally accepted naming conventions -->

    <module name="PackageName">
      <!-- Validates identifiers for package names against the supplied expression. -->
      <!-- Here the default checkstyle rule restricts package name parts to
        seven characters, this is not in line with common practice at Google. -->
      <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]{1,})*$"/>
      <property name="severity" value="warning"/>
    </module>

    <module name="TypeNameCheck">
      <!-- Validates static, final fields against the expression "^[A-Z][a-zA-Z0-9]*$". -->
      <metadata name="altname" value="TypeName"/>
      <property name="severity" value="warning"/>
    </module>

    <module name="ConstantNameCheck">
      <!-- Validates non-private, static, final fields against the supplied
        public/package final fields "^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$". -->
      <metadata name="altname" value="ConstantName"/>
      <property name="applyToPublic" value="true"/>
      <property name="applyToProtected" value="true"/>
      <property name="applyToPackage" value="true"/>
      <property name="applyToPrivate" value="false"/>
      <property name="format" value="^([A-Z][A-Z0-9]*(_[A-Z0-9]+)*|FLAG_.*)$"/>
      <message key="name.invalidPattern"
        value="Variable ''{0}'' should be in ALL_CAPS (if it is a constant) or be private (otherwise)."/>
      <property name="severity" value="warning"/>
    </module>

    <module name="StaticVariableNameCheck">
      <!-- Validates static, non-final fields against the supplied expression
        "^[a-z][a-zA-Z0-9]*_?$". -->
      <metadata name="altname" value="StaticVariableName"/>
      <property name="applyToPublic" value="true"/>
      <property name="applyToProtected" value="true"/>
      <property name="applyToPackage" value="true"/>
      <property name="applyToPrivate" value="true"/>
      <property name="format" value="^[a-z][a-zA-Z0-9]*_?$"/>
      <property name="severity" value="warning"/>
    </module>

    <module name="MemberNameCheck">
      <!-- Validates non-static members against the supplied expression. -->
      <metadata name="altname" value="MemberName"/>
      <property name="applyToPublic" value="true"/>
      <property name="applyToProtected" value="true"/>
      <property name="applyToPackage" value="true"/>
      <property name="applyToPrivate" value="true"/>
      <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
      <property name="severity" value="warning"/>
    </module>

    <module name="MethodNameCheck">
      <!-- Validates identifiers for method names. -->
      <metadata name="altname" value="MethodName"/>
      <property name="format" value="^[a-z][a-zA-Z0-9]*(_[a-zA-Z0-9]+)*$"/>
      <property name="severity" value="warning"/>
    </module>

    <module name="ParameterName">
      <!-- Validates identifiers for method parameters against the expression
        "^[a-z][a-zA-Z0-9]*$". -->
      <property name="severity" value="warning"/>
    </module>

    <module name="LocalFinalVariableName">
      <!-- Validates identifiers for local final variables against the expression
        "^[a-z][a-zA-Z0-9]*$". -->
      <property name="severity" value="warning"/>
    </module>

    <module name="LocalVariableName">
      <!-- Validates identifiers for local variables against the expression
        "^[a-z][a-zA-Z0-9]*$". -->
      <property name="severity" value="warning"/>
    </module>


    <!-- LENGTH and CODING CHECKS -->

    <module name="LineLength">
      <!-- Checks if a line is too long. -->
      <property name="max"
        value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.max}"
        default="100"/>
      <property name="severity" value="error"/>

      <!-- The default ignore pattern exempts the following elements: - import
        statements - long URLs inside comments -->

      <property name="ignorePattern"
        value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.ignorePattern}"
        default="^(package .*;\s*)|(import .*;\s*)|( *\* *https?://.*)$"/>
    </module>

    <module name="LeftCurly">
      <!-- Checks for placement of the left curly brace ('{'). -->
      <property name="severity" value="warning"/>
    </module>

    <module name="RightCurly">
      <!-- Checks right curlies on CATCH, ELSE, and TRY blocks are on the same
        line. e.g., the following example is fine: <pre> if { ... } else </pre> -->
      <!-- This next example is not fine: <pre> if { ... } else </pre> -->
      <property name="option" value="same"/>
      <property name="severity" value="warning"/>
    </module>

    <!-- Checks for braces around if and else blocks -->
    <module name="NeedBraces">
      <property name="severity" value="warning"/>
      <property name="tokens"
        value="LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO"/>
    </module>

    <module name="UpperEll">
      <!-- Checks that long constants are defined with an upper ell. -->
      <property name="severity" value="error"/>
    </module>

    <module name="FallThrough">
      <!-- Warn about falling through to the next case statement. Similar to
        javac -Xlint:fallthrough, but the check is suppressed if a single-line comment
        on the last non-blank line preceding the fallen-into case contains 'fall
        through' (or some other variants which we don't publicized to promote consistency). -->
      <property name="reliefPattern"
        value="fall through|Fall through|fallthru|Fallthru|falls through|Falls through|fallthrough|Fallthrough|No break|NO break|no break|continue on"/>
      <property name="severity" value="error"/>
    </module>


    <!-- MODIFIERS CHECKS -->

    <module name="ModifierOrder">
      <!-- Warn if modifier order is inconsistent with JLS3 8.1.1, 8.3.1, and
        8.4.3. The prescribed order is: public, protected, private, abstract, static,
        final, transient, volatile, synchronized, native, strictfp -->
    </module>


    <!-- WHITESPACE CHECKS -->

    <module name="WhitespaceAround">
      <!-- Checks that various tokens are surrounded by whitespace. This includes
        most binary operators and keywords followed by regular or curly braces. -->
      <property name="tokens"
        value="ASSIGN, BAND, BAND_ASSIGN, BOR,
        BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN,
        EQUAL, GE, GT, LAND, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE,
        LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF, LITERAL_RETURN,
        LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS,
        MINUS_ASSIGN, MOD, MOD_ASSIGN, NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION,
        SL, SL_ASSIGN, SR_ASSIGN, STAR, STAR_ASSIGN"/>
      <property name="severity" value="error"/>
    </module>

    <module name="WhitespaceAfter">
      <!-- Checks that commas, semicolons and typecasts are followed by whitespace. -->
      <property name="tokens" value="COMMA, SEMI, TYPECAST"/>
    </module>

    <module name="NoWhitespaceAfter">
      <!-- Checks that there is no whitespace after various unary operators.
        Linebreaks are allowed. -->
      <property name="tokens"
        value="BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS,
        UNARY_PLUS"/>
      <property name="allowLineBreaks" value="true"/>
      <property name="severity" value="error"/>
    </module>

    <module name="NoWhitespaceBefore">
      <!-- Checks that there is no whitespace before various unary operators.
        Linebreaks are allowed. -->
      <property name="tokens" value="SEMI, DOT, POST_DEC, POST_INC"/>
      <property name="allowLineBreaks" value="true"/>
      <property name="severity" value="error"/>
    </module>

    <module name="ParenPad">
      <!-- Checks that there is no whitespace before close parens or after open
        parens. -->
      <property name="severity" value="warning"/>
    </module>

    <module name="Indentation">
      <!-- Checks code indentation -->
      <property name="basicOffset" value="2"/>
      <property name="caseIndent" value="2"/>
    </module>

    <module name="EmptyCatchBlock">
      <property name="exceptionVariableName" value="expected"/>
    </module>
    <module name="CommentsIndentation"/>
    <module name="UnusedImports"/>
    <module name="RedundantImport"/>
    <module name="RedundantModifier"/>
    <module name="AvoidStarImport"/>
  </module>
</module>