Use AdoptOpenJDK JDK 8 and 11

Ref scala/scala-dev#587

Author: eed3si9n

.travis.yml

@@ -1,7 +1,7 @@
+dist: xenial
+group: stable
+
 language: scala
-jdk:
-  - openjdk8
-  - openjdk11
 
 scala:
   - 2.11.12
@@ -18,14 +18,26 @@ env:
     - secure: "OIVtcj7AHZr8Grpf03ZmZsygcADewiYIvSnRwLYCx+5AqOzs39EZ68DsIOxi7wEXVUbVj5RvLXpKzLX3iN+UszLOQRoFPFQyyn+3Y50f8T2aRxdZtInzXn0sCVTj4Hhd/zbKl1W+2Nh3Sqazab7tFoQVzEyYqhcPeiNRMF7h+aY="
   matrix:
     # The empty SCALAJS_VERSION will only compile for the JVM
-    - SCALAJS_VERSION=
-    - SCALAJS_VERSION=0.6.28
-    - SCALAJS_VERSION=1.0.0-M8
+    - SCALAJS_VERSION=         ADOPTOPENJDK=8
+    - SCALAJS_VERSION=0.6.28   ADOPTOPENJDK=8
+    - SCALAJS_VERSION=1.0.0-M8 ADOPTOPENJDK=11
 
 matrix:
   include:
-    - env: SCALANATIVE_VERSION=0.3.9
-      jdk: openjdk8
+    - env: SCALANATIVE_VERSION=0.3.9 ADOPTOPENJDK=8
+
+before_install:
+  # adding $HOME/.sdkman to cache would create an empty directory, which interferes with the initial installation
+  - "[[ -d $HOME/.sdkman/bin/ ]] || rm -rf $HOME/.sdkman/"
+  - curl -sL https://get.sdkman.io | bash
+  - echo sdkman_auto_answer=true > $HOME/.sdkman/etc/config
+  - source "$HOME/.sdkman/bin/sdkman-init.sh"
+
+install:
+  - sdk install java $(sdk list java | grep -o "$ADOPTOPENJDK\.[0-9\.]*hs-adpt" | tail -1)
+  - unset JAVA_HOME
+  - java -Xmx32m -version
+  - javac -Xmx32m -version
 
 script: admin/build.sh
 
@@ -40,6 +52,7 @@ before_cache:
   - find $HOME/.ivy2/cache -name "ivydata-*.properties" | xargs rm
 cache:
   directories:
-  - $HOME/.ivy2/cache
-  - $HOME/.sbt/boot
-  - $HOME/.sbt/launchers
+    - $HOME/.ivy2/cache
+    - $HOME/.sbt/boot
+    - $HOME/.sbt/launchers
+    - $HOME/.sdkman