Added oraclejdk9 to the build matrix.
diff --git a/.travis.yml b/.travis.yml
index ab7097b..ed758e1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,7 @@
   - mvn -B -U -f build-pom.xml verify --fail-at-end -Dsource.skip=true -Dmaven.javadoc.skip=true
 
 jdk:
+  - oraclejdk9
   - oraclejdk8
 
 env: