language: java
jdk:
  - openjdk8
  - oraclejdk8
after_success:
  - mvn clean test coveralls:jacoco

language: java
jdk:
  - openjdk8
  - oraclejdk9
after_success:
  - mvn clean test coveralls:jacoco

Fix CI: upgrade TravisCI from Oracle JDK 8 to 9
Fix CI: upgrade TravisCI from Oracle JDK 8 to 9

Indeed, Oracle JDK 8 does not seem to be supported anymore:

```
Installing oraclejdk8
$ export JAVA_HOME=~/oraclejdk8
$ export PATH="$JAVA_HOME/bin:$PATH"
$ ~/bin/install-jdk.sh --target "/home/travis/oraclejdk8" --workspace "/home/travis/.cache/install-jdk" --feature "8" --license "BCL"
Ignoring license option: BCL -- using GPLv2+CE by default
install-jdk.sh 2020-06-02
Expected feature release number in range of 9 to 16, but got: 8
The command "~/bin/install-jdk.sh --target "/home/travis/oraclejdk8" --workspace "/home/travis/.cache/install-jdk" --feature "8" --license "BCL"" failed and exited with 3 during .
Your build has been stopped.
```

Source: https://travis-ci.org/github/marccarre/properties-files-maven-plugin/jobs/699877359
