Travis: Switch to Ubuntu 16.04 & OpenJDK, sudo keyword deprecated (#373)

* Switch to Ubuntu 18.04, sudo keyword deprecated

* Switch to Ubuntu 16.04 and OpenJDK

Author: fbenz

.travis.yml

@@ -1,9 +1,8 @@
 language: java
-sudo: false
-dist: trusty
+dist: xenial
 jdk:
-- oraclejdk8
-- oraclejdk9
+- openjdk8
+- openjdk9
 - openjdk10
 - openjdk11
 before_cache:
@@ -23,17 +22,17 @@ script:
 - cd samples
 - mvn install -B -V
 - cd java-webmvc && ./gradlew check && cd ..
-- test "$TRAVIS_JDK_VERSION" = "oraclejdk8" && cd kotlin-webmvc && ./gradlew check && cd .. || (exit 0)
+- test "$TRAVIS_JDK_VERSION" = "openjdk8" && cd kotlin-webmvc && ./gradlew check && cd .. || (exit 0)
 after_success:
 - echo $GPG_SECRET_KEYS | base64 --decode | gpg --import
 - cd $TRAVIS_BUILD_DIR
 - echo TRAVIS_PULL_REQUEST=\"$TRAVIS_PULL_REQUEST\"
 - echo TRAVIS_JDK_VERSION=\"$TRAVIS_JDK_VERSION\"
 - test "$TRAVIS_PULL_REQUEST" = "false"
-  && test "$TRAVIS_JDK_VERSION" = "oraclejdk8"
+  && test "$TRAVIS_JDK_VERSION" = "openjdk8"
   && mvn deploy --settings travis-settings.xml -DskipTests=true -B -V
 - test "$TRAVIS_PULL_REQUEST" = "false"
-  && test "$TRAVIS_JDK_VERSION" = "oraclejdk9"
+  && test "$TRAVIS_JDK_VERSION" = "openjdk9"
   && cd spring-auto-restdocs-json-doclet-jdk9
   && mvn deploy --settings ../travis-settings.xml -DskipTests=true -B -V
 branches: