diff --git a/.travis.yml b/.travis.yml
index deca7d67da9..9b34dc2e493 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -21,7 +21,7 @@ cache:
   apt: true
   directories:
     - .spark-dist
-    - ${HOME}/.m2
+    - ${HOME}/.m2/repository/.cache/maven-download-plugin
     - ${HOME}/R
     -  zeppelin-web/node
     -  zeppelin-web/node_modules
@@ -42,6 +42,10 @@ matrix:
     - jdk: "oraclejdk7"
       env: SCALA_VER="2.11" PROFILE="-Prat" BUILD_FLAG="clean" TEST_FLAG="org.apache.rat:apache-rat-plugin:check" TEST_PROJECTS=""
 
+    # Test checkstyle with spark 2.0.0 and scala 2.11
+    - jdk: "oraclejdk7"
+      env: CHECKSTYLE=1 SCALA_VER="2.11" SPARK_VER="2.0.0" HADOOP_VER="2.3" PROFILE="-Pspark-2.0 -Phadoop-2.3 -Ppyspark -Pscala-2.11" BUILD_FLAG="package -DskipTests -DskipRat" TEST_FLAG="validate -Pcheckstyle" TEST_PROJECTS=""
+
     # Test all modules with spark 2.0.0 and scala 2.11
     - jdk: "oraclejdk7"
       env: SCALA_VER="2.11" SPARK_VER="2.0.0" HADOOP_VER="2.3" PROFILE="-Pspark-2.0 -Phadoop-2.3 -Ppyspark -Psparkr -Pscalding -Pexamples -Pscala-2.11" BUILD_FLAG="package -Pbuild-distr -DskipRat" TEST_FLAG="verify -Pusing-packaged-distr -DskipRat" TEST_PROJECTS=""
@@ -75,6 +79,7 @@ matrix:
       env: PYTHON="3" SCALA_VER="2.11" SPARK_VER="2.0.0" HADOOP_VER="2.3" PROFILE="-Pspark-2.0 -Phadoop-2.3 -Ppyspark -Pscala-2.11" BUILD_FLAG="package -pl spark,python -am -DskipTests -DskipRat" TEST_FLAG="verify -DskipRat" TEST_PROJECTS="-pl zeppelin-interpreter,zeppelin-display,spark-dependencies,spark,python -Dtest=org.apache.zeppelin.spark.PySpark*Test,org.apache.zeppelin.python.* -Dpyspark.test.exclude='' -DfailIfNoTests=false"
 
 before_install:
+  - mkdir -p .spark-dist
   - echo "MAVEN_OPTS='-Xms1024M -Xmx2048M -XX:MaxPermSize=1024m -XX:-UseGCOverheadLimit'" >> ~/.mavenrc
   - ./testing/install_external_dependencies.sh
   - ls -la .spark-dist ${HOME}/.m2/repository/.cache/maven-download-plugin || true
@@ -82,6 +87,8 @@ before_install:
   - "/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1600x1024x16"
   - ./dev/change_scala_version.sh $SCALA_VER
   - source ~/.environ
+  - cat ~/.m2/settings.xml || true
+  - sed -i.bak -e 's|https://nexus.codehaus.org/snapshots/|https://oss.sonatype.org/content/repositories/codehaus-snapshots/|g' ~/.m2/settings.xml # travis CI 4629
 
 install:
   - mvn -Dorg.slf4j.simpleLogger.defaultLogLevel=warn $BUILD_FLAG $PROFILE -B
diff --git a/_tools/checkstyle.xml b/_tools/checkstyle.xml
index 618d74d14e2..c3e2d7255fa 100644
--- a/_tools/checkstyle.xml
+++ b/_tools/checkstyle.xml
@@ -15,268 +15,211 @@ limitations under the License.
 -->
 
 <!DOCTYPE module PUBLIC
-    "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
-    "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+          "-//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"> Checks for out of order import statements 
-			<property name="severity" value="warning"/> <property name="groups" value="com.google,android,junit,net,org,java,javax"/> 
-			This ensures that static imports go first <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="JavadocType">
-			<property name="scope" value="protected" />
-			<property name="severity" value="error" />
-		</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" />
-                </module>
-	</module>
+<!--
+    Checkstyle configuration that checks the Google coding conventions from Google Java Style
+    that can be found at https://google.github.io/styleguide/javaguide.html.
+
+    Checkstyle is very configurable. Be sure to read the documentation at
+    http://checkstyle.sf.net (or in your downloaded distribution).
+
+    To completely disable a check, just comment it out or delete it from the file.
+
+    Authors: Max Vetrenko, Ruslan Diachenko, Roman Ivanov.
+ -->
+
+<module name = "Checker">
+    <property name="charset" value="UTF-8"/>
+
+    <property name="severity" value="warning"/>
+
+    <property name="fileExtensions" value="java, properties, xml"/>
+    <!-- Checks for whitespace                               -->
+    <!-- See http://checkstyle.sf.net/config_whitespace.html -->
+        <module name="FileTabCharacter">
+            <property name="eachLine" value="true"/>
+        </module>
+
+    <module name="TreeWalker">
+        <module name="OuterTypeFilename"/>
+        <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>
+        <module name="AvoidEscapedUnicodeCharacters">
+            <property name="allowEscapesForControlCharacters" value="true"/>
+            <property name="allowByTailComment" value="true"/>
+            <property name="allowNonPrintableEscapes" value="true"/>
+        </module>
+        <module name="LineLength">
+            <property name="max" value="100"/>
+            <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
+        </module>
+        <module name="AvoidStarImport"/>
+        <module name="OneTopLevelClass"/>
+        <module name="NoLineWrap"/>
+        <module name="EmptyBlock">
+            <property name="option" value="TEXT"/>
+            <property name="tokens" value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH"/>
+        </module>
+        <module name="NeedBraces"/>
+        <module name="LeftCurly">
+            <property name="maxLineLength" value="100"/>
+        </module>
+        <module name="RightCurly"/>
+        <module name="RightCurly">
+            <property name="option" value="alone"/>
+            <property name="tokens" value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO, STATIC_INIT, INSTANCE_INIT"/>
+        </module>
+        <module name="WhitespaceAround">
+            <property name="allowEmptyConstructors" value="true"/>
+            <property name="allowEmptyMethods" value="true"/>
+            <property name="allowEmptyTypes" value="true"/>
+            <property name="allowEmptyLoops" value="true"/>
+            <message key="ws.notFollowed"
+             value="WhitespaceAround: ''{0}'' is not followed by whitespace. Empty blocks may only be represented as '{}' when not part of a multi-block statement (4.1.3)"/>
+             <message key="ws.notPreceded"
+             value="WhitespaceAround: ''{0}'' is not preceded with whitespace."/>
+        </module>
+        <module name="OneStatementPerLine"/>
+        <module name="MultipleVariableDeclarations"/>
+        <module name="ArrayTypeStyle"/>
+        <module name="MissingSwitchDefault"/>
+        <module name="FallThrough"/>
+        <module name="UpperEll"/>
+        <module name="ModifierOrder"/>
+        <module name="EmptyLineSeparator">
+            <property name="allowNoEmptyLineBetweenFields" value="true"/>
+        </module>
+        <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 name="PackageName">
+            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
+            <message key="name.invalidPattern"
+             value="Package name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="TypeName">
+            <message key="name.invalidPattern"
+             value="Type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="MemberName">
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+             value="Member name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="ParameterName">
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+             value="Parameter name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="CatchParameterName">
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+             value="Catch parameter name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="LocalVariableName">
+            <property name="tokens" value="VARIABLE_DEF"/>
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
+            <property name="allowOneCharVarInForLoop" value="true"/>
+            <message key="name.invalidPattern"
+             value="Local variable name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="ClassTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+             value="Class type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="MethodTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+             value="Method type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="InterfaceTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+             value="Interface type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="NoFinalizer"/>
+        <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>
+        <module name="Indentation">
+            <property name="basicOffset" value="2"/>
+            <property name="braceAdjustment" value="0"/>
+            <property name="caseIndent" value="2"/>
+            <property name="throwsIndent" value="4"/>
+            <property name="lineWrappingIndentation" value="4"/>
+            <property name="arrayInitIndent" value="2"/>
+        </module>
+        <module name="AbbreviationAsWordInName">
+            <property name="ignoreFinal" value="false"/>
+            <property name="allowedAbbreviationLength" value="1"/>
+        </module>
+        <module name="OverloadMethodsDeclarationOrder"/>
+        <module name="VariableDeclarationUsageDistance"/>
+        <module name="CustomImportOrder">
+            <property name="specialImportsRegExp" value="com.google"/>
+            <property name="sortImportsInGroupAlphabetically" value="true"/>
+            <property name="customImportOrderRules" value="STATIC###SPECIAL_IMPORTS###THIRD_PARTY_PACKAGE###STANDARD_JAVA_PACKAGE"/>
+        </module>
+        <module name="MethodParamPad"/>
+        <module name="OperatorWrap">
+            <property name="option" value="NL"/>
+            <property name="tokens" value="BAND, BOR, BSR, BXOR, DIV, EQUAL, GE, GT, LAND, LE, LITERAL_INSTANCEOF, LOR, LT, MINUS, MOD, NOT_EQUAL, PLUS, QUESTION, SL, SR, STAR "/>
+        </module>
+        <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>
+        <module name="NonEmptyAtclauseDescription"/>
+        <module name="JavadocTagContinuationIndentation"/>
+        <module name="SummaryJavadoc">
+            <property name="forbiddenSummaryFragments" value="^@return the *|^This method returns |^A [{]@code [a-zA-Z0-9]+[}]( is a )"/>
+        </module>
+        <module name="JavadocParagraph"/>
+        <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>
+        <module name="JavadocMethod">
+            <property name="scope" value="public"/>
+            <property name="allowMissingParamTags" value="true"/>
+            <property name="allowMissingThrowsTags" value="true"/>
+            <property name="allowMissingReturnTag" value="true"/>
+            <property name="minLineCount" value="2"/>
+            <property name="allowedAnnotations" value="Override, Test"/>
+            <property name="allowThrowsTagsForSubclasses" value="true"/>
+        </module>
+        <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>
+        <module name="SingleLineJavadoc">
+            <property name="ignoreInlineTags" value="false"/>
+        </module>
+        <module name="EmptyCatchBlock">
+            <property name="exceptionVariableName" value="expected"/>
+        </module>
+        <module name="CommentsIndentation"/>
+    </module>
 </module>
diff --git a/alluxio/src/main/java/org/apache/zeppelin/alluxio/AlluxioInterpreter.java b/alluxio/src/main/java/org/apache/zeppelin/alluxio/AlluxioInterpreter.java
index 79e10b6f95d..03e2dc2cdc5 100644
--- a/alluxio/src/main/java/org/apache/zeppelin/alluxio/AlluxioInterpreter.java
+++ b/alluxio/src/main/java/org/apache/zeppelin/alluxio/AlluxioInterpreter.java
@@ -70,8 +70,8 @@ public AlluxioInterpreter(Properties property) {
 
   @Override
   public void open() {
-    logger.info("Starting Alluxio shell to connect to " + alluxioMasterHostname +
-      " on port " + alluxioMasterPort);
+    logger.info("Starting Alluxio shell to connect to " + alluxioMasterHostname
+        + " on port " + alluxioMasterPort);
 
     System.setProperty(ALLUXIO_MASTER_HOSTNAME, alluxioMasterHostname);
     System.setProperty(ALLUXIO_MASTER_PORT, alluxioMasterPort);
diff --git a/bigquery/src/main/java/org/apache/zeppelin/bigquery/BigQueryInterpreter.java b/bigquery/src/main/java/org/apache/zeppelin/bigquery/BigQueryInterpreter.java
index 33e196003b0..d91422acfe5 100644
--- a/bigquery/src/main/java/org/apache/zeppelin/bigquery/BigQueryInterpreter.java
+++ b/bigquery/src/main/java/org/apache/zeppelin/bigquery/BigQueryInterpreter.java
@@ -263,8 +263,8 @@ private InterpreterResult executeSql(String sql) {
   }
 
   //Function to run the SQL on bigQuery service
-  public static Iterator<GetQueryResultsResponse> run(final String queryString, 
-    final String projId, final long wTime, final long maxRows) 
+  public static Iterator<GetQueryResultsResponse> run(final String queryString,
+      final String projId, final long wTime, final long maxRows)
       throws IOException {
     try {
       QueryResponse query = service.jobs().query(
diff --git a/elasticsearch/src/main/java/org/apache/zeppelin/elasticsearch/ElasticsearchInterpreter.java b/elasticsearch/src/main/java/org/apache/zeppelin/elasticsearch/ElasticsearchInterpreter.java
index 549b5f25efd..406a9689b6a 100644
--- a/elasticsearch/src/main/java/org/apache/zeppelin/elasticsearch/ElasticsearchInterpreter.java
+++ b/elasticsearch/src/main/java/org/apache/zeppelin/elasticsearch/ElasticsearchInterpreter.java
@@ -77,25 +77,25 @@ public class ElasticsearchInterpreter extends Interpreter {
   private static Logger logger = LoggerFactory.getLogger(ElasticsearchInterpreter.class);
 
   private static final String HELP = "Elasticsearch interpreter:\n"
-    + "General format: <command> /<indices>/<types>/<id> <option> <JSON>\n"
-    + "  - indices: list of indices separated by commas (depends on the command)\n"
-    + "  - types: list of document types separated by commas (depends on the command)\n"
-    + "Commands:\n"
-    + "  - search /indices/types <query>\n"
-    + "    . indices and types can be omitted (at least, you have to provide '/')\n"
-    + "    . a query is either a JSON-formatted query, nor a lucene query\n"
-    + "  - size <value>\n"
-    + "    . defines the size of the result set (default value is in the config)\n"
-    + "    . if used, this command must be declared before a search command\n"
-    + "  - count /indices/types <query>\n"
-    + "    . same comments as for the search\n"
-    + "  - get /index/type/id\n"
-    + "  - delete /index/type/id\n"
-    + "  - index /ndex/type/id <json-formatted document>\n"
-    + "    . the id can be omitted, elasticsearch will generate one";
+      + "General format: <command> /<indices>/<types>/<id> <option> <JSON>\n"
+      + "  - indices: list of indices separated by commas (depends on the command)\n"
+      + "  - types: list of document types separated by commas (depends on the command)\n"
+      + "Commands:\n"
+      + "  - search /indices/types <query>\n"
+      + "    . indices and types can be omitted (at least, you have to provide '/')\n"
+      + "    . a query is either a JSON-formatted query, nor a lucene query\n"
+      + "  - size <value>\n"
+      + "    . defines the size of the result set (default value is in the config)\n"
+      + "    . if used, this command must be declared before a search command\n"
+      + "  - count /indices/types <query>\n"
+      + "    . same comments as for the search\n"
+      + "  - get /index/type/id\n"
+      + "  - delete /index/type/id\n"
+      + "  - index /ndex/type/id <json-formatted document>\n"
+      + "    . the id can be omitted, elasticsearch will generate one";
 
   protected static final List<String> COMMANDS = Arrays.asList(
-    "count", "delete", "get", "help", "index", "search");
+      "count", "delete", "get", "help", "index", "search");
 
   private static final Pattern FIELD_NAME_PATTERN = Pattern.compile("\\[\\\\\"(.+)\\\\\"\\](.*)");
 
@@ -122,7 +122,7 @@ public ElasticsearchInterpreter(Properties property) {
     } catch (NumberFormatException e) {
       this.resultSize = 10;
       logger.error("Unable to parse " + ELASTICSEARCH_RESULT_SIZE + " : " +
-        property.get(ELASTICSEARCH_RESULT_SIZE), e);
+          property.get(ELASTICSEARCH_RESULT_SIZE), e);
     }
   }
 
@@ -131,9 +131,9 @@ public void open() {
     try {
       logger.info("prop={}", getProperty());
       final Settings settings = Settings.settingsBuilder()
-        .put("cluster.name", clusterName)
-        .put(getProperty())
-        .build();
+          .put("cluster.name", clusterName)
+          .put(getProperty())
+          .build();
       client = TransportClient.builder().settings(settings).build()
         .addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName(host), port));
     }
@@ -280,8 +280,8 @@ private InterpreterResult processGet(String[] urlItems) {
     }
 
     final GetResponse response = client
-      .prepareGet(urlItems[0], urlItems[1], urlItems[2])
-      .get();
+        .prepareGet(urlItems[0], urlItems[1], urlItems[2])
+        .get();
     if (response.isExists()) {
       final String json = gson.toJson(response.getSource());
 
@@ -351,9 +351,9 @@ private InterpreterResult processIndex(String[] urlItems, String data) {
     }
 
     final IndexResponse response = client
-      .prepareIndex(urlItems[0], urlItems[1], urlItems.length == 2 ? null : urlItems[2])
-      .setSource(data)
-      .get();
+        .prepareIndex(urlItems[0], urlItems[1], urlItems.length == 2 ? null : urlItems[2])
+        .setSource(data)
+        .get();
 
     return new InterpreterResult(
       InterpreterResult.Code.SUCCESS,
@@ -378,8 +378,8 @@ private InterpreterResult processDelete(String[] urlItems) {
     }
 
     final DeleteResponse response = client
-      .prepareDelete(urlItems[0], urlItems[1], urlItems[2])
-      .get();
+        .prepareDelete(urlItems[0], urlItems[1], urlItems[2])
+        .get();
 
     if (response.isFound()) {
       return new InterpreterResult(
@@ -394,7 +394,7 @@ private InterpreterResult processDelete(String[] urlItems) {
   private SearchResponse searchData(String[] urlItems, String query, int size) {
 
     final SearchRequestBuilder reqBuilder = new SearchRequestBuilder(
-      client, SearchAction.INSTANCE);
+        client, SearchAction.INSTANCE);
     reqBuilder.setIndices();
 
     if (urlItems.length >= 1) {
@@ -510,9 +510,8 @@ private String buildSearchHitsResponseMessage(SearchHit[] hits) {
         final Matcher fieldNameMatcher = FIELD_NAME_PATTERN.matcher(fieldName);
         if (fieldNameMatcher.matches()) {
           flattenMap.put(fieldNameMatcher.group(1) + fieldNameMatcher.group(2),
-            flattenJsonMap.get(fieldName));
-        }
-        else {
+              flattenJsonMap.get(fieldName));
+        } else {
           flattenMap.put(fieldName, flattenJsonMap.get(fieldName));
         }
       }
diff --git a/jdbc/src/main/java/org/apache/zeppelin/jdbc/JDBCInterpreter.java b/jdbc/src/main/java/org/apache/zeppelin/jdbc/JDBCInterpreter.java
index 7e2fb115058..e9756f854de 100644
--- a/jdbc/src/main/java/org/apache/zeppelin/jdbc/JDBCInterpreter.java
+++ b/jdbc/src/main/java/org/apache/zeppelin/jdbc/JDBCInterpreter.java
@@ -256,7 +256,7 @@ private UsernamePassword getUsernamePassword(InterpreterContext interpreterConte
 
   public JDBCUserConfigurations getJDBCConfiguration(String user) {
     JDBCUserConfigurations jdbcUserConfigurations =
-      jdbcUserConfigurationsMap.get(user);
+        jdbcUserConfigurationsMap.get(user);
 
     if (jdbcUserConfigurations == null) {
       jdbcUserConfigurations = new JDBCUserConfigurations();
@@ -279,7 +279,7 @@ private void setUserProperty(String propertyKey, InterpreterContext interpreterC
     String user = interpreterContext.getAuthenticationInfo().getUser();
 
     JDBCUserConfigurations jdbcUserConfigurations =
-      getJDBCConfiguration(user);
+        getJDBCConfiguration(user);
     jdbcUserConfigurations.setPropertyMap(propertyKey, basePropretiesMap.get(propertyKey));
 
     if (existAccountInBaseProperty()) {
@@ -288,7 +288,7 @@ private void setUserProperty(String propertyKey, InterpreterContext interpreterC
     jdbcUserConfigurations.cleanUserProperty(propertyKey);
 
     UsernamePassword usernamePassword = getUsernamePassword(interpreterContext,
-      getEntityName(interpreterContext.getReplName()));
+        getEntityName(interpreterContext.getReplName()));
     if (usernamePassword != null) {
       jdbcUserConfigurations.setUserProperty(propertyKey, usernamePassword);
     } else {
@@ -299,10 +299,10 @@ private void setUserProperty(String propertyKey, InterpreterContext interpreterC
   private void createConnectionPool(String url, String user, String propertyKey,
       Properties properties) throws SQLException, ClassNotFoundException {
     ConnectionFactory connectionFactory =
-      new DriverManagerConnectionFactory(url, properties);
+        new DriverManagerConnectionFactory(url, properties);
 
     PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(
-      connectionFactory, null);
+        connectionFactory, null);
     ObjectPool connectionPool = new GenericObjectPool(poolableConnectionFactory);
 
     poolableConnectionFactory.setPool(connectionPool);
@@ -531,7 +531,7 @@ public void cancel(InterpreterContext context) {
     logger.info("Cancel current query statement.");
     String paragraphId = context.getParagraphId();
     JDBCUserConfigurations jdbcUserConfigurations =
-      getJDBCConfiguration(context.getAuthenticationInfo().getUser());
+        getJDBCConfiguration(context.getAuthenticationInfo().getUser());
     try {
       jdbcUserConfigurations.cancelStatement(paragraphId);
     } catch (SQLException e) {
diff --git a/lens/src/main/java/org/apache/zeppelin/lens/LensInterpreter.java b/lens/src/main/java/org/apache/zeppelin/lens/LensInterpreter.java
index 17e3a46c68f..fb95fd6793a 100644
--- a/lens/src/main/java/org/apache/zeppelin/lens/LensInterpreter.java
+++ b/lens/src/main/java/org/apache/zeppelin/lens/LensInterpreter.java
@@ -75,10 +75,10 @@ public class LensInterpreter extends Interpreter {
   };
 
   private static Pattern s_queryExecutePattern = Pattern.compile(".*query\\s+execute\\s+(.*)");
-  private static Map<String, ExecutionDetail> s_paraToQH = 
-    new ConcurrentHashMap<> (); //tracks paragraphId -> Lens QueryHandle
+  private static Map<String, ExecutionDetail> s_paraToQH =
+      new ConcurrentHashMap<> (); //tracks paragraphId -> Lens QueryHandle
   private static Map<LensClient, Boolean> s_clientMap =
-    new ConcurrentHashMap<>();
+      new ConcurrentHashMap<>();
 
   private int m_maxResults;
   private int m_maxThreads;
@@ -100,14 +100,14 @@ public LensInterpreter(Properties property) {
       m_lensConf.set(LENS_PERSIST_RESULTSET, property.get(LENS_PERSIST_RESULTSET).toString());
       try {
         m_maxResults = Integer.parseInt(property.get(ZEPPELIN_MAX_ROWS).toString());
-      } catch (NumberFormatException|NullPointerException e) {
+      } catch (NumberFormatException | NullPointerException e) {
         m_maxResults = 1000;
-        s_logger.error("unable to parse " + ZEPPELIN_MAX_ROWS + " :" 
-          + property.get(ZEPPELIN_MAX_ROWS), e);
+        s_logger.error("unable to parse " + ZEPPELIN_MAX_ROWS + " :"
+            + property.get(ZEPPELIN_MAX_ROWS), e);
       }
       try {
         m_maxThreads = Integer.parseInt(property.get(ZEPPELIN_LENS_CONCURRENT_SESSIONS).toString());
-      } catch (NumberFormatException|NullPointerException e) {
+      } catch (NumberFormatException | NullPointerException e) {
         m_maxThreads = 10;
         s_logger.error("unable to parse " + ZEPPELIN_LENS_CONCURRENT_SESSIONS + " :" 
             + property.get(ZEPPELIN_LENS_CONCURRENT_SESSIONS), e);
@@ -265,11 +265,11 @@ public InterpreterResult interpret(String input, InterpreterContext context) {
           && res.getResult().toString().trim().matches("[a-z0-9-]+")) {
         // setup query progress tracking
         qh = res.getResult().toString();
-        s_paraToQH.put(context.getParagraphId(), 
-          new ExecutionDetail(qh, lensClient, shell));
+        s_paraToQH.put(context.getParagraphId(),
+            new ExecutionDetail(qh, lensClient, shell));
         String getResultsCmd = "query results --async false " + qh;
-        s_logger.info("executing query results command : " + context.getParagraphId() 
-          + " : " + getResultsCmd);
+        s_logger.info("executing query results command : " + context.getParagraphId()
+            + " : " + getResultsCmd);
         res = shell.executeCommand(getResultsCmd); 
         s_paraToQH.remove(context.getParagraphId());
       }
@@ -321,7 +321,7 @@ private String formatResult(String st, CommandResult result) {
       }
     }
     if (s_queryExecutePattern.matcher(st.toLowerCase()).find() &&
-      result.getResult().toString().contains(" rows process in (")) {
+        result.getResult().toString().contains(" rows process in (")) {
       sb.append("%table ");
     }
     if (sb.length() > 0) {
@@ -347,11 +347,11 @@ public void cancel(InterpreterContext context) {
       s_clientMap.put(lensClient, true);
       s_logger.info("invoke query kill (" + context.getParagraphId() + ") " + qh);
       CommandResult res = shell.executeCommand("query kill " + qh);
-      s_logger.info("query kill returned (" + context.getParagraphId() + ") " + qh 
-        + " with: " + res.getResult());
+      s_logger.info("query kill returned (" + context.getParagraphId() + ") " + qh
+          + " with: " + res.getResult());
     } catch (Exception e) {
       s_logger.error("unable to kill query ("
-        + context.getParagraphId() + ") " + qh, e);
+          + context.getParagraphId() + ") " + qh, e);
     } finally {
       try {
         if (lensClient != null) {
diff --git a/lens/src/main/java/org/apache/zeppelin/lens/LensJLineShellComponent.java b/lens/src/main/java/org/apache/zeppelin/lens/LensJLineShellComponent.java
index 7bf20592651..9a16074336b 100644
--- a/lens/src/main/java/org/apache/zeppelin/lens/LensJLineShellComponent.java
+++ b/lens/src/main/java/org/apache/zeppelin/lens/LensJLineShellComponent.java
@@ -37,8 +37,8 @@
 /**
  * workaround for https://github.com/spring-projects/spring-shell/issues/73
  */
-public class LensJLineShellComponent extends JLineShell 
-  implements SmartLifecycle, ApplicationContextAware, InitializingBean {
+public class LensJLineShellComponent extends JLineShell
+    implements SmartLifecycle, ApplicationContextAware, InitializingBean {
 
   @Autowired
   private CommandLine commandLine;
@@ -101,15 +101,15 @@ public boolean isRunning() {
   @SuppressWarnings("rawtypes")
   public void afterPropertiesSet() {
 
-    Map<String, CommandMarker> commands = 
-      BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext,
-        CommandMarker.class);
+    Map<String, CommandMarker> commands =
+        BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext,
+            CommandMarker.class);
     for (CommandMarker command : commands.values()) {
       getSimpleParser().add(command);
     }
 
     Map<String, Converter> converters = BeanFactoryUtils
-      .beansOfTypeIncludingAncestors(applicationContext, Converter.class);
+        .beansOfTypeIncludingAncestors(applicationContext, Converter.class);
     for (Converter<?> converter : converters.values()) {
       getSimpleParser().add(converter);
     }
@@ -169,7 +169,7 @@ public void customizePlugin() {
    */
   protected String getHistoryFileName() {
     HistoryFileNameProvider historyFileNameProvider = PluginUtils
-      .getHighestPriorityProvider(this.applicationContext, HistoryFileNameProvider.class);
+        .getHighestPriorityProvider(this.applicationContext, HistoryFileNameProvider.class);
     String providerHistoryFileName = historyFileNameProvider.getHistoryFileName();
     if (providerHistoryFileName != null) {
       return providerHistoryFileName;
@@ -186,7 +186,7 @@ protected String getHistoryFileName() {
    */
   protected String getPromptText() {
     PromptProvider promptProvider = PluginUtils
-      .getHighestPriorityProvider(this.applicationContext, PromptProvider.class);
+        .getHighestPriorityProvider(this.applicationContext, PromptProvider.class);
     String providerPromptText = promptProvider.getPrompt();
     if (providerPromptText != null) {
       return providerPromptText;
@@ -206,7 +206,7 @@ protected String getPromptText() {
   private String[] getBannerText() {
     String[] bannerText = new String[4];
     BannerProvider provider = PluginUtils
-      .getHighestPriorityProvider(this.applicationContext, BannerProvider.class);
+        .getHighestPriorityProvider(this.applicationContext, BannerProvider.class);
     bannerText[0] = provider.getBanner();
     bannerText[1] = provider.getWelcomeMessage();
     bannerText[2] = provider.getVersion();
diff --git a/pom.xml b/pom.xml
index fd14e84cd2b..8aa5fdd923f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -416,7 +416,14 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-checkstyle-plugin</artifactId>
-          <version>2.13</version>
+          <version>2.17</version>
+          <dependencies>
+            <dependency>
+              <groupId>com.puppycrawl.tools</groupId>
+              <artifactId>checkstyle</artifactId>
+              <version>6.19</version>
+            </dependency>
+          </dependencies>
         </plugin>
 
         <plugin>
@@ -737,6 +744,22 @@
       </build>
     </profile>
 
+    <profile>
+      <id>checkstyle</id>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-checkstyle-plugin</artifactId>
+            <configuration>
+              <consoleOutput>true</consoleOutput>
+              <!--TODO:enable violation <violationSeverity>warn</violationSeverity>-->
+            </configuration>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
+
     <profile>
       <id>rat</id>
       <activation>
diff --git a/scalding/src/main/java/org/apache/zeppelin/scalding/ScaldingInterpreter.java b/scalding/src/main/java/org/apache/zeppelin/scalding/ScaldingInterpreter.java
index 282cd2e734f..bb9cbe38bef 100644
--- a/scalding/src/main/java/org/apache/zeppelin/scalding/ScaldingInterpreter.java
+++ b/scalding/src/main/java/org/apache/zeppelin/scalding/ScaldingInterpreter.java
@@ -55,14 +55,14 @@ public class ScaldingInterpreter extends Interpreter {
   static final String MAX_OPEN_INSTANCES_DEFAULT = "50";
 
   public static final List NO_COMPLETION =
-    Collections.unmodifiableList(new ArrayList<>());
+      Collections.unmodifiableList(new ArrayList<>());
 
   static {
     Interpreter.register(
-      "scalding",
-      "scalding",
-      ScaldingInterpreter.class.getName(),
-      new InterpreterPropertyBuilder()
+        "scalding",
+        "scalding",
+        ScaldingInterpreter.class.getName(),
+        new InterpreterPropertyBuilder()
         .add(ARGS_STRING, ARGS_STRING_DEFAULT, "Arguments for scalding REPL")
         .add(MAX_OPEN_INSTANCES, MAX_OPEN_INSTANCES_DEFAULT,
                 "Maximum number of open interpreter instances")
@@ -123,10 +123,10 @@ public InterpreterResult interpret(String cmd, InterpreterContext contextInterpr
 
     if (interpreter == null) {
       logger.error(
-        "interpreter == null, open may not have been called because max.open.instances reached");
+          "interpreter == null, open may not have been called because max.open.instances reached");
       return new InterpreterResult(Code.ERROR,
-        "interpreter == null\n" +
-        "open may not have been called because max.open.instances reached"
+        "interpreter == null\n"
+            + "open may not have been called because max.open.instances reached"
       );
     }
     if (cmd == null || cmd.trim().length() == 0) {
@@ -147,10 +147,10 @@ public InterpreterResult interpret(String cmd, InterpreterContext contextInterpr
         final String cmd1 = cmd;
         final InterpreterContext contextInterpreter1 = contextInterpreter;
         PrivilegedExceptionAction<InterpreterResult> action =
-          new PrivilegedExceptionAction<InterpreterResult>() {
-            public InterpreterResult run() throws Exception {
-              return interpret(cmd1.split("\n"), contextInterpreter1);
-            }
+            new PrivilegedExceptionAction<InterpreterResult>() {
+              public InterpreterResult run() throws Exception {
+                return interpret(cmd1.split("\n"), contextInterpreter1);
+              }
           };
         interpreterResult = ugi.doAs(action);
       } catch (Exception e) {
diff --git a/shell/src/main/java/org/apache/zeppelin/shell/ShellInterpreter.java b/shell/src/main/java/org/apache/zeppelin/shell/ShellInterpreter.java
index 838c6f15358..1c760d1ef77 100644
--- a/shell/src/main/java/org/apache/zeppelin/shell/ShellInterpreter.java
+++ b/shell/src/main/java/org/apache/zeppelin/shell/ShellInterpreter.java
@@ -90,8 +90,8 @@ public InterpreterResult interpret(String cmd, InterpreterContext contextInterpr
       executor.setWatchdog(new ExecuteWatchdog(Long.valueOf(getProperty(TIMEOUT_PROPERTY))));
       executors.put(contextInterpreter.getParagraphId(), executor);
       int exitVal = executor.execute(cmdLine);
-      LOGGER.info("Paragraph " + contextInterpreter.getParagraphId() 
-        + " return with exit value: " + exitVal);
+      LOGGER.info("Paragraph " + contextInterpreter.getParagraphId()
+          + " return with exit value: " + exitVal);
       return new InterpreterResult(Code.SUCCESS, outStream.toString());
     } catch (ExecuteException e) {
       int exitValue = e.getExitValue();
@@ -101,8 +101,8 @@ public InterpreterResult interpret(String cmd, InterpreterContext contextInterpr
       if (exitValue == 143) {
         code = Code.INCOMPLETE;
         message += "Paragraph received a SIGTERM.\n";
-        LOGGER.info("The paragraph " + contextInterpreter.getParagraphId() 
-          + " stopped executing: " + message);
+        LOGGER.info("The paragraph " + contextInterpreter.getParagraphId()
+            + " stopped executing: " + message);
       }
       message += "ExitValue: " + exitValue;
       return new InterpreterResult(code, message);
diff --git a/shell/src/main/java/org/apache/zeppelin/shell/security/ShellSecurityImpl.java b/shell/src/main/java/org/apache/zeppelin/shell/security/ShellSecurityImpl.java
index bb3ce861f78..f11576fbd10 100644
--- a/shell/src/main/java/org/apache/zeppelin/shell/security/ShellSecurityImpl.java
+++ b/shell/src/main/java/org/apache/zeppelin/shell/security/ShellSecurityImpl.java
@@ -36,15 +36,15 @@ public class ShellSecurityImpl {
   public static void createSecureConfiguration(Properties properties, String shell) {
 
     String authType = properties.getProperty("zeppelin.shell.auth.type")
-      .trim().toUpperCase();
+        .trim().toUpperCase();
 
     switch (authType) {
         case "KERBEROS":
           CommandLine cmdLine = CommandLine.parse(shell);
           cmdLine.addArgument("-c", false);
           String kinitCommand = String.format("kinit -k -t %s %s",
-            properties.getProperty("zeppelin.shell.keytab.location"),
-            properties.getProperty("zeppelin.shell.principal"));
+              properties.getProperty("zeppelin.shell.keytab.location"),
+              properties.getProperty("zeppelin.shell.principal"));
           cmdLine.addArgument(kinitCommand, false);
           DefaultExecutor executor = new DefaultExecutor();
 
diff --git a/spark-dependencies/pom.xml b/spark-dependencies/pom.xml
index 04b6983fb03..9698039ab48 100644
--- a/spark-dependencies/pom.xml
+++ b/spark-dependencies/pom.xml
@@ -823,7 +823,7 @@
           <plugin>
             <groupId>com.googlecode.maven-download-plugin</groupId>
             <artifactId>download-maven-plugin</artifactId>
-            <version>1.2.1</version>
+            <version>1.3.0</version>
             <executions>
               <execution>
                 <id>download-pyspark-files</id>
@@ -832,6 +832,8 @@
                   <goal>wget</goal>
                 </goals>
                 <configuration>
+                  <readTimeOut>1800000</readTimeOut>
+                  <retries>30</retries>
                   <url>${spark.download.url}</url>
                   <outputDirectory>${spark.dist.cache}</outputDirectory>
                 </configuration>
@@ -902,7 +904,7 @@
           <plugin>
             <groupId>com.googlecode.maven-download-plugin</groupId>
             <artifactId>download-maven-plugin</artifactId>
-            <version>1.2.1</version>
+            <version>1.3.0</version>
             <executions>
               <execution>
                 <id>download-sparkr-files</id>
@@ -911,6 +913,8 @@
                   <goal>wget</goal>
                 </goals>
                 <configuration>
+                  <readTimeOut>1800000</readTimeOut>
+                  <retries>30</retries>
                   <url>${spark.bin.download.url}</url>
                   <unpack>true</unpack>
                   <outputDirectory>${project.build.directory}/spark-bin-dist</outputDirectory>
diff --git a/spark/src/main/java/org/apache/zeppelin/spark/DepInterpreter.java b/spark/src/main/java/org/apache/zeppelin/spark/DepInterpreter.java
index 478d0bc794c..a39b8c4152a 100644
--- a/spark/src/main/java/org/apache/zeppelin/spark/DepInterpreter.java
+++ b/spark/src/main/java/org/apache/zeppelin/spark/DepInterpreter.java
@@ -206,7 +206,7 @@ private Results.Result interpret(String line) {
 
   public Object getValue(String name) {
     Object ret = Utils.invokeMethod(
-      intp, "valueOfTerm", new Class[]{String.class}, new Object[]{name});
+        intp, "valueOfTerm", new Class[]{String.class}, new Object[]{name});
     if (ret instanceof None) {
       return null;
     } else if (ret instanceof Some) {
diff --git a/spark/src/main/java/org/apache/zeppelin/spark/SparkInterpreter.java b/spark/src/main/java/org/apache/zeppelin/spark/SparkInterpreter.java
index e8c76bcccd4..2edb26e0ad1 100644
--- a/spark/src/main/java/org/apache/zeppelin/spark/SparkInterpreter.java
+++ b/spark/src/main/java/org/apache/zeppelin/spark/SparkInterpreter.java
@@ -415,7 +415,7 @@ public SparkContext createSparkContext_1() {
         // continue instead of: throw new InterpreterException(e);
         // Newer Spark versions (like the patched CDH5.7.0 one) don't contain this method
         logger.warn(String.format("Spark method classServerUri not available due to: [%s]",
-          e.getMessage()));
+            e.getMessage()));
       }
     }
 
@@ -490,7 +490,7 @@ private void setupConfForPySpark(SparkConf conf) {
 
     //Only one of py4j-0.9-src.zip and py4j-0.8.2.1-src.zip should exist
     String[] pythonLibs = new String[]{"pyspark.zip", "py4j-0.9-src.zip", "py4j-0.8.2.1-src.zip",
-      "py4j-0.10.1-src.zip", "py4j-0.10.3-src.zip"};
+        "py4j-0.10.1-src.zip", "py4j-0.10.3-src.zip"};
     ArrayList<String> pythonLibUris = new ArrayList<>();
     for (String lib : pythonLibs) {
       File libFile = new File(pysparkPath, lib);
@@ -1155,9 +1155,9 @@ public InterpreterResult interpretInput(String[] lines, InterpreterContext conte
         String nextLine = linesToRun[l + 1].trim();
         boolean continuation = false;
         if (nextLine.isEmpty()
-           || nextLine.startsWith("//")         // skip empty line or comment
-           || nextLine.startsWith("}")
-           || nextLine.startsWith("object")) {  // include "} object" for Scala companion object
+            || nextLine.startsWith("//")         // skip empty line or comment
+            || nextLine.startsWith("}")
+            || nextLine.startsWith("object")) {  // include "} object" for Scala companion object
           continuation = true;
         } else if (!inComment && nextLine.startsWith("/*")) {
           inComment = true;
@@ -1448,10 +1448,10 @@ private Object createHttpServer(File outputDir) {
       Constructor<?> constructor = getClass().getClassLoader()
           .loadClass("org.apache.spark.HttpServer")
           .getConstructor(new Class[]{
-            SparkConf.class, File.class, SecurityManager.class, int.class, String.class});
+              SparkConf.class, File.class, SecurityManager.class, int.class, String.class});
 
       return constructor.newInstance(new Object[] {
-        conf, outputDir, new SecurityManager(conf), 0, "HTTP Server"});
+          conf, outputDir, new SecurityManager(conf), 0, "HTTP Server"});
     } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException |
         InstantiationException | InvocationTargetException e) {
       // fallback to old constructor
@@ -1460,9 +1460,9 @@ private Object createHttpServer(File outputDir) {
         constructor = getClass().getClassLoader()
             .loadClass("org.apache.spark.HttpServer")
             .getConstructor(new Class[]{
-              File.class, SecurityManager.class, int.class, String.class});
+                File.class, SecurityManager.class, int.class, String.class});
         return constructor.newInstance(new Object[] {
-          outputDir, new SecurityManager(conf), 0, "HTTP Server"});
+            outputDir, new SecurityManager(conf), 0, "HTTP Server"});
       } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException |
           InstantiationException | InvocationTargetException e1) {
         logger.error(e1.getMessage(), e1);
diff --git a/zeppelin-interpreter/src/main/java/org/apache/zeppelin/dep/DependencyResolver.java b/zeppelin-interpreter/src/main/java/org/apache/zeppelin/dep/DependencyResolver.java
index 03f6b323185..c4ec04b5028 100644
--- a/zeppelin-interpreter/src/main/java/org/apache/zeppelin/dep/DependencyResolver.java
+++ b/zeppelin-interpreter/src/main/java/org/apache/zeppelin/dep/DependencyResolver.java
@@ -159,7 +159,7 @@ private List<File> loadFromMvn(String artifact, Collection<String> excludes)
    */
   @Override
   public List<ArtifactResult> getArtifactsWithDep(String dependency,
-    Collection<String> excludes) throws RepositoryException {
+      Collection<String> excludes) throws RepositoryException {
     Artifact artifact = new DefaultArtifact(dependency);
     DependencyFilter classpathFilter = DependencyFilterUtils.classpathFilter(JavaScopes.COMPILE);
     PatternExclusionsDependencyFilter exclusionFilter =
diff --git a/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreter.java b/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreter.java
index 1ffba42ba77..bd927ab76c0 100644
--- a/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreter.java
+++ b/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreter.java
@@ -239,7 +239,7 @@ public synchronized void init() {
           property.put("zeppelin.interpreter.localRepo", localRepoPath);
         }
         client.createInterpreter(groupId, sessionKey,
-          getClassName(), (Map) property, userName);
+            getClassName(), (Map) property, userName);
         // Push angular object loaded from JSON file to remote interpreter
         if (!interpreterGroup.isAngularRegistryPushed()) {
           pushAngularObjectRegistryToRemote(client);
diff --git a/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreterServer.java b/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreterServer.java
index ca611454c53..483b5071be7 100644
--- a/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreterServer.java
+++ b/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreterServer.java
@@ -58,9 +58,8 @@
  * Entry point for Interpreter process.
  * Accepting thrift connections from ZeppelinServer.
  */
-public class RemoteInterpreterServer
-  extends Thread
-  implements RemoteInterpreterService.Iface, AngularObjectRegistryListener {
+public class RemoteInterpreterServer extends Thread
+        implements RemoteInterpreterService.Iface, AngularObjectRegistryListener {
   Logger logger = LoggerFactory.getLogger(RemoteInterpreterServer.class);
 
   InterpreterGroup interpreterGroup;
diff --git a/zeppelin-interpreter/src/test/resources/log4j.properties b/zeppelin-interpreter/src/test/resources/log4j.properties
index d8a783974e3..b81d6729f87 100644
--- a/zeppelin-interpreter/src/test/resources/log4j.properties
+++ b/zeppelin-interpreter/src/test/resources/log4j.properties
@@ -26,4 +26,4 @@ log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c:%L - %m%n
 #
 
 # Root logger option
-log4j.rootLogger=INFO, stdout
\ No newline at end of file
+log4j.rootLogger=INFO, stdout
diff --git a/zeppelin-server/src/main/java/org/apache/zeppelin/realm/ActiveDirectoryGroupRealm.java b/zeppelin-server/src/main/java/org/apache/zeppelin/realm/ActiveDirectoryGroupRealm.java
index d89719cdf47..1309bcad4c1 100644
--- a/zeppelin-server/src/main/java/org/apache/zeppelin/realm/ActiveDirectoryGroupRealm.java
+++ b/zeppelin-server/src/main/java/org/apache/zeppelin/realm/ActiveDirectoryGroupRealm.java
@@ -117,9 +117,9 @@ private String getSystemPassword() {
       try {
         Configuration configuration = new Configuration();
         configuration.set(CredentialProviderFactory.CREDENTIAL_PROVIDER_PATH,
-          this.hadoopSecurityCredentialPath);
+            this.hadoopSecurityCredentialPath);
         CredentialProvider provider =
-          CredentialProviderFactory.getProviders(configuration).get(0);
+            CredentialProviderFactory.getProviders(configuration).get(0);
         CredentialProvider.CredentialEntry credEntry = provider.getCredentialEntry(
             KEYSTORE_PASS);
         if (credEntry != null) {
diff --git a/zeppelin-server/src/main/java/org/apache/zeppelin/rest/CredentialRestApi.java b/zeppelin-server/src/main/java/org/apache/zeppelin/rest/CredentialRestApi.java
index 74412c44862..1095f6345c5 100755
--- a/zeppelin-server/src/main/java/org/apache/zeppelin/rest/CredentialRestApi.java
+++ b/zeppelin-server/src/main/java/org/apache/zeppelin/rest/CredentialRestApi.java
@@ -66,7 +66,7 @@ public CredentialRestApi(Credentials credentials) {
   @PUT
   public Response putCredentials(String message) throws IOException, IllegalArgumentException {
     Map<String, String> messageMap = gson.fromJson(message,
-      new TypeToken<Map<String, String>>(){}.getType());
+        new TypeToken<Map<String, String>>(){}.getType());
     String entity = messageMap.get("entity");
     String username = messageMap.get("username");
     String password = messageMap.get("password");
diff --git a/zeppelin-server/src/main/java/org/apache/zeppelin/server/ZeppelinServer.java b/zeppelin-server/src/main/java/org/apache/zeppelin/server/ZeppelinServer.java
index eec99736073..c131b8d8e8e 100644
--- a/zeppelin-server/src/main/java/org/apache/zeppelin/server/ZeppelinServer.java
+++ b/zeppelin-server/src/main/java/org/apache/zeppelin/server/ZeppelinServer.java
@@ -316,7 +316,7 @@ public Set<Object> getSingletons() {
     singletons.add(root);
 
     NotebookRestApi notebookApi
-      = new NotebookRestApi(notebook, notebookWsServer, noteSearchService);
+        = new NotebookRestApi(notebook, notebookWsServer, noteSearchService);
     singletons.add(notebookApi);
 
     NotebookRepoRestApi notebookRepoApi = new NotebookRepoRestApi(notebookRepo, notebookWsServer);
diff --git a/zeppelin-server/src/main/java/org/apache/zeppelin/socket/NotebookServer.java b/zeppelin-server/src/main/java/org/apache/zeppelin/socket/NotebookServer.java
index 709434596c2..f21ea93b087 100644
--- a/zeppelin-server/src/main/java/org/apache/zeppelin/socket/NotebookServer.java
+++ b/zeppelin-server/src/main/java/org/apache/zeppelin/socket/NotebookServer.java
@@ -474,14 +474,14 @@ public void unicastNoteJobInfo(NotebookSocket conn, Message fromMessage) throws
     addConnectionToNote(JOB_MANAGER_SERVICE.JOB_MANAGER_PAGE.getKey(), conn);
     AuthenticationInfo subject = new AuthenticationInfo(fromMessage.principal);
     List<Map<String, Object>> noteJobs = notebook()
-      .getJobListByUnixTime(false, 0, subject);
+        .getJobListByUnixTime(false, 0, subject);
     Map<String, Object> response = new HashMap<>();
 
     response.put("lastResponseUnixTime", System.currentTimeMillis());
     response.put("jobs", noteJobs);
 
     conn.send(serializeMessage(new Message(OP.LIST_NOTE_JOBS)
-      .put("noteJobs", response)));
+        .put("noteJobs", response)));
   }
 
   public void broadcastUpdateNoteJobInfo(long lastUpdateUnixTime) throws IOException {
@@ -498,7 +498,7 @@ public void broadcastUpdateNoteJobInfo(long lastUpdateUnixTime) throws IOExcepti
     response.put("jobs", noteJobs != null ? noteJobs : new LinkedList<>());
 
     broadcast(JOB_MANAGER_SERVICE.JOB_MANAGER_PAGE.getKey(),
-      new Message(OP.LIST_UPDATE_NOTE_JOBS).put("noteRunningJobs", response));
+        new Message(OP.LIST_UPDATE_NOTE_JOBS).put("noteRunningJobs", response));
   }
 
   public void unsubscribeNoteJobInfo(NotebookSocket conn) {
@@ -1178,8 +1178,8 @@ private InterpreterGroup findInterpreterGroupForParagraph(Note note, String para
   }
 
   private void pushAngularObjectToRemoteRegistry(String noteId, String paragraphId,
-     String varName, Object varValue, RemoteAngularObjectRegistry remoteRegistry,
-     String interpreterGroupId, NotebookSocket conn) {
+       String varName, Object varValue, RemoteAngularObjectRegistry remoteRegistry,
+       String interpreterGroupId, NotebookSocket conn) {
 
     final AngularObject ao = remoteRegistry.addAndNotifyRemoteProcess(varName, varValue,
             noteId, paragraphId);
@@ -1194,8 +1194,8 @@ private void pushAngularObjectToRemoteRegistry(String noteId, String paragraphId
   }
 
   private void removeAngularFromRemoteRegistry(String noteId, String paragraphId,
-    String varName, RemoteAngularObjectRegistry remoteRegistry,
-    String interpreterGroupId, NotebookSocket conn) {
+      String varName, RemoteAngularObjectRegistry remoteRegistry,
+      String interpreterGroupId, NotebookSocket conn) {
     final AngularObject ao = remoteRegistry.removeAndNotifyRemoteProcess(varName, noteId,
             paragraphId);
     this.broadcastExcept(
@@ -1208,8 +1208,8 @@ private void removeAngularFromRemoteRegistry(String noteId, String paragraphId,
   }
 
   private void pushAngularObjectToLocalRepo(String noteId, String paragraphId, String varName,
-    Object varValue, AngularObjectRegistry registry,
-    String interpreterGroupId, NotebookSocket conn) {
+      Object varValue, AngularObjectRegistry registry,
+      String interpreterGroupId, NotebookSocket conn) {
     AngularObject angularObject = registry.get(varName, noteId, paragraphId);
     if (angularObject == null) {
       angularObject = registry.add(varName, varValue, noteId, paragraphId);
@@ -1227,7 +1227,7 @@ private void pushAngularObjectToLocalRepo(String noteId, String paragraphId, Str
   }
 
   private void removeAngularObjectFromLocalRepo(String noteId, String paragraphId, String varName,
-    AngularObjectRegistry registry, String interpreterGroupId, NotebookSocket conn) {
+      AngularObjectRegistry registry, String interpreterGroupId, NotebookSocket conn) {
     final AngularObject removed = registry.remove(varName, noteId, paragraphId);
     if (removed != null) {
       this.broadcastExcept(
@@ -1330,10 +1330,10 @@ private void runParagraph(NotebookSocket conn, HashSet<String> userAndRoles, Not
     p.setAuthenticationInfo(authenticationInfo);
 
     Map<String, Object> params = (Map<String, Object>) fromMessage
-       .get("params");
+        .get("params");
     p.settings.setParams(params);
     Map<String, Object> config = (Map<String, Object>) fromMessage
-       .get("config");
+        .get("config");
     p.setConfig(config);
     // if it's the last paragraph, let's add a new one
     boolean isTheLastParagraph = note.isLastParagraph(p.getId());
@@ -1399,7 +1399,7 @@ private void checkpointNote(NotebookSocket conn, Notebook notebook,
     if (revision != null) {
       List<Revision> revisions = notebook.listRevisionHistory(noteId, subject);
       conn.send(serializeMessage(new Message(OP.LIST_REVISION_HISTORY)
-        .put("revisionList", revisions)));
+          .put("revisionList", revisions)));
     }
   }
 
@@ -1410,7 +1410,7 @@ private void listRevisionHistory(NotebookSocket conn, Notebook notebook,
     List<Revision> revisions = notebook.listRevisionHistory(noteId, subject);
 
     conn.send(serializeMessage(new Message(OP.LIST_REVISION_HISTORY)
-      .put("revisionList", revisions)));
+        .put("revisionList", revisions)));
   }
 
   private void getNoteByRevision(NotebookSocket conn, Notebook notebook, Message fromMessage)
diff --git a/zeppelin-zengine/src/main/java/org/apache/zeppelin/interpreter/InterpreterFactory.java b/zeppelin-zengine/src/main/java/org/apache/zeppelin/interpreter/InterpreterFactory.java
index e4ea916f4a4..4ffe03dab01 100644
--- a/zeppelin-zengine/src/main/java/org/apache/zeppelin/interpreter/InterpreterFactory.java
+++ b/zeppelin-zengine/src/main/java/org/apache/zeppelin/interpreter/InterpreterFactory.java
@@ -409,7 +409,7 @@ private void loadFromFile() throws IOException {
       interpreterSettingObject = interpreterSettingsRef.get(setting.getGroup());
       if (interpreterSettingObject == null) {
         logger.warn("can't get InterpreterSetting " +
-          "Information From loaded Interpreter Setting Ref - {} ", setting.getGroup());
+            "Information From loaded Interpreter Setting Ref - {} ", setting.getGroup());
         continue;
       }
       depClassPath = interpreterSettingObject.getPath();
diff --git a/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/NotebookImportDeserializer.java b/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/NotebookImportDeserializer.java
index 86e0f0bf77e..47c3eca43eb 100644
--- a/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/NotebookImportDeserializer.java
+++ b/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/NotebookImportDeserializer.java
@@ -34,14 +34,14 @@
  */
 public class NotebookImportDeserializer implements JsonDeserializer<Date> {
   private static final String[] DATE_FORMATS = new String[] {
-    "yyyy-MM-dd'T'HH:mm:ssZ",
-    "MMM d, yyyy h:mm:ss a",
-    "MMM dd, yyyy HH:mm:ss"
+      "yyyy-MM-dd'T'HH:mm:ssZ",
+      "MMM d, yyyy h:mm:ss a",
+      "MMM dd, yyyy HH:mm:ss"
   };
 
   @Override
   public Date deserialize(JsonElement jsonElement, Type typeOF,
-    JsonDeserializationContext context) throws JsonParseException {
+      JsonDeserializationContext context) throws JsonParseException {
     for (String format : DATE_FORMATS) {
       try {
         return new SimpleDateFormat(format, Locale.US).parse(jsonElement.getAsString());
diff --git a/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/Paragraph.java b/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/Paragraph.java
index 56d64ef09c6..f584433edcc 100644
--- a/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/Paragraph.java
+++ b/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/Paragraph.java
@@ -226,8 +226,8 @@ public List<InterpreterCompletion> getInterpreterCompletion() {
   public List<InterpreterCompletion> completion(String buffer, int cursor) {
     String lines[] = buffer.split(System.getProperty("line.separator"));
     if (lines.length > 0
-      && lines[0].startsWith("%")
-      && cursor <= lines[0].trim().length()) {
+        && lines[0].startsWith("%")
+        && cursor <= lines[0].trim().length()) {
 
       int idx = lines[0].indexOf(' ');
       if (idx < 0 || (idx > 0 && cursor <= idx)) {
@@ -303,8 +303,8 @@ protected Object jobRun() throws Throwable {
     }
     if (this.noteHasUser() && this.noteHasInterpreters()) {
       if (intp != null &&
-        interpreterHasUser(intp) &&
-        isUserAuthorizedToAccessInterpreter(intp.getOption()) == false) {
+          interpreterHasUser(intp) &&
+          isUserAuthorizedToAccessInterpreter(intp.getOption()) == false) {
         logger.error("{} has no permission for {} ", authenticationInfo.getUser(), repl);
         return new InterpreterResult(Code.ERROR, authenticationInfo.getUser() +
           " has no permission for " + getRequiredReplName());
diff --git a/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/repo/NotebookRepoSync.java b/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/repo/NotebookRepoSync.java
index 445776ea56a..f646ed7d1c5 100644
--- a/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/repo/NotebookRepoSync.java
+++ b/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/repo/NotebookRepoSync.java
@@ -437,7 +437,7 @@ public Revision checkpoint(String noteId, String checkpointMsg, AuthenticationIn
         allRepoCheckpoints.add(getRepo(i).checkpoint(noteId, checkpointMsg, subject));
       } catch (IOException e) {
         LOG.warn("Couldn't checkpoint in {} storage with index {} for note {}",
-          getRepo(i).getClass().toString(), i, noteId);
+            getRepo(i).getClass().toString(), i, noteId);
         errorMessage += "Error on storage class " + getRepo(i).getClass().toString() +
           " with index " + i + " : " + e.getMessage() + "\n";
         errorCount++;
diff --git a/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/utility/IdHashes.java b/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/utility/IdHashes.java
index 98aaac8a756..e3b6bda93a7 100644
--- a/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/utility/IdHashes.java
+++ b/zeppelin-zengine/src/main/java/org/apache/zeppelin/notebook/utility/IdHashes.java
@@ -27,8 +27,8 @@
  */
 public class IdHashes {
   private static final char[] DICTIONARY = new char[] {'1', '2', '3', '4', '5', '6', '7', '8', '9',
-    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
-    'W', 'X', 'Y', 'Z'};
+      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
+      'W', 'X', 'Y', 'Z'};
 
   /**
    * encodes the given string into the base of the dictionary provided in the constructor.