Example Checkstyle rule for Accumulo Public API

pom.xml

    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-checkstyle-plugin</artifactId>
          <version>2.14</version>
        </plugin>
      </plugins>
    </pluginManagement>
    <plugins> 
     <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-checkstyle-plugin</artifactId>
        <configuration>
          <checkstyleRules>
            <module name="Checker">
              <module name="TreeWalker">
                <module name="AvoidStarImport"/>
                <module name="RegexpSinglelineJava">
                  <!--check that only Accumulo public APIs are imported-->
                  <property name="format" value="import\s+org\.apache\.accumulo\.(.*\.(impl|thrift)\..*|(?!core|minicluster).*|core\.(?!client|data|security\.Authorizations|security\.ColumnVisibility).*|core\.data\.(?!Key|Mutation|Value|Range|Condition|ConditionalMutation|ByteSequence|PartialKey|ColumnUpdate).*)"/>
                  <property name="ignoreComments" value="true"/>
                  <property name="message" value="Accumulo non-public classes imported"/>
                </module>
              </module>
            </module>
          </checkstyleRules>
          <failOnViolation>true</failOnViolation>
         </configuration>
         <executions>
           <execution>
             <id>check-style</id>
             <goals>
               <goal>check</goal>
             </goals>
           </execution>
         </executions>
      </plugin>
   </plugins>

What this rule checks for differs from what specified in the Accumulo README as the public API. Opened ACCUMULO-3657 to address this.