Use the maven compiler plugin to tell IDEs what version of Java to use.

pom.xml

@@ -27,6 +27,7 @@
       <tag>1.1.0</tag>
    </scm>
    <properties>
+      <java.version>11</java.version>
       <solr.base.version>6.6.5</solr.base.version>
       <solr.version>${solr.base.version}-patched</solr.version>
       <!-- The location to download the solr zip file from. -->
@@ -39,6 +40,20 @@
       <module>search-services</module>
       <module>insight-engine</module>
    </modules>
+   <build>
+      <plugins>
+         <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-compiler-plugin</artifactId>
+            <version>3.8.1</version>
+            <configuration>
+               <release>${java.version}</release>
+               <showWarnings>true</showWarnings>
+               <showDeprecation>true</showDeprecation>
+            </configuration>
+         </plugin>
+      </plugins>
+   </build>
    <dependencies>
      <!-- Used to declare false positives for FindBugs -->
       <dependency>