HADOOP-14986. Enforce JDK limitations.

hadoop-project/pom.xml

@@ -1507,6 +1507,32 @@
             </goals>
           </execution>
         </executions>
+      </plugin>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>animal-sniffer-maven-plugin</artifactId>
+        <version>1.16</version>
+        <executions>
+          <execution>
+            <id>signature-check</id>
+            <phase>verify</phase>
+            <goals>
+              <goal>check</goal>
+            </goals>
+          </execution>
+        </executions>
+        <configuration>
+          <signature>
+            <groupId>org.codehaus.mojo.signature</groupId>
+            <artifactId>java18</artifactId>
+            <version>1.0</version>
+          </signature>
+          <ignores>
+            <ignore>sun.misc.*</ignore>
+            <ignore>sun.net.*</ignore>
+            <ignore>sun.nio.ch.*</ignore>
+          </ignores>
+        </configuration>
       </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>