<plugins>
 <plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>3.6.0</version>
  <configuration>
   <source>1.9</source>
   <target>1.9</target>
   <compilerArgument>-Xlint:all</compilerArgument>
  </configuration>
 </plugin>
</plugins>

<plugins>
 <plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>3.6.0</version>
  <configuration>
   <source>1.9</source>
   <target>1.9</target>
   <compilerArgument>-Xlint:all</compilerArgument>
  </configuration>
 </plugin>
</plugins>