Replace Java 15 with Java 16 in Travis CI.
diff --git a/.travis.yml b/.travis.yml
index 51bc4cc..cd7c717 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,7 +20,7 @@
   - openjdk7

   - openjdk8

   - openjdk11

-  - openjdk15

+  - openjdk16

   - openjdk-ea

 

 after_success: