[FLINK-6732] [java] Activate strict checkstyle for flink-java

docs/internals/ide_setup.md

@@ -107,7 +107,7 @@ You can scan an entire module by opening the Checkstyle tools window and
 clicking the "Check Module" button. The scan should report no errors.
 
 <span class="label label-info">Note</span> Some modules are not fully covered by checkstyle,
-which include `flink-core`, `flink-java`, `flink-optimizer`, and `flink-runtime`.
+which include `flink-core`, `flink-optimizer`, and `flink-runtime`.
 Nevertheless please make sure that code you add/modify in these modules still conforms to the checkstyle rules.
 
 ## Eclipse

flink-java/pom.xml

@@ -85,35 +85,6 @@ under the License.
 
 	<build>
 		<plugins>
-			<plugin>
-				<groupId>org.apache.maven.plugins</groupId>
-				<artifactId>maven-checkstyle-plugin</artifactId>
-				<version>2.17</version>
-				<dependencies>
-					<dependency>
-						<groupId>com.puppycrawl.tools</groupId>
-						<artifactId>checkstyle</artifactId>
-						<version>6.19</version>
-					</dependency>
-				</dependencies>
-				<executions>
-					<execution>
-						<id>validate</id>
-						<phase>validate</phase>
-						<goals>
-							<goal>check</goal>
-						</goals>
-					</execution>
-				</executions>
-
-				<configuration>
-					<configLocation>/tools/maven/checkstyle.xml</configLocation>
-					<suppressionsLocation>/tools/maven/suppressions-java.xml</suppressionsLocation>
-					<includeTestSourceDirectory>true</includeTestSourceDirectory>
-					<logViolationsToConsole>true</logViolationsToConsole>
-					<failOnViolation>true</failOnViolation>
-				</configuration>
-			</plugin>
 
 			<!-- activate API compatibility checks -->
 			<plugin>