Build with JDK 8 on travis

.travis.yml

@@ -2,7 +2,7 @@ language: java
 sudo: false
 
 jdk:
-  - oraclejdk7
+  - oraclejdk8
 
 install: true
 script: ./travis.sh
@@ -21,3 +21,11 @@ notifications:
   email: false
   webhooks:
     - secure: "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"
+
+addons:
+  apt:
+    packages:
+      # upgrade java 8 as the default version 1.8.0_31 prevents from compiling sources
+      # https://github.com/travis-ci/travis-ci/issues/4042
+      - oracle-java8-installer
+