Replace Java 15 with Java 16 in Travis CI.
diff --git a/.travis.yml b/.travis.yml
index 66fb005..1ebced0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,7 +19,7 @@
 jdk:

   - openjdk8

   - openjdk11

-  - openjdk15

+  - openjdk16

 

 after_success:

   - mvn -V clean cobertura:cobertura coveralls:report --no-transfer-progress