Use AdoptOpenJDK JDK 8 and 11

.travis.yml

@@ -1,9 +1,5 @@
 language: scala
 
-jdk:
-  - openjdk8
-  - openjdk11
-
 scala:
   # note that 2.13 is on the 2.13.x branch instead
   - 2.11.12
@@ -17,6 +13,22 @@ env:
     - secure: "lx2qFeFxh9AFmyHR7hH4Qf9flIEx8VgYj6ebzuxp1cc1ZZiXHC1256x0bHFDUH9bhJACOazOrco/+v6MBAriBkWxLBc98FrC6OkVeQMFW2ffWSBuHRclilKsQA/Lsgc81Wg+WV105hOqUNAkTXgroblInNt+KS+DhC/8FVoh9ZY="
     # SONA_PASS
     - secure: "FZC+FZnBNeklA150vW5QDZJ5J7t+DExJrgyXWM46Wh0MobjH8cvydgC3qatItb0rDBV8l7zO1LDwl2KEi92aefw2a8E49z6qVOHgUXiI3SAx7M0UO0FFeKPmTXCLcBlbnGLcUqNjIZfuIEufQvPblKTl8qN4eMmcMn9jsNzJr28="
+  matrix:
+    - ADOPTOPENJDK=8
+    - ADOPTOPENJDK=11
+
+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" | head -1)
+  - unset JAVA_HOME
+  - java -Xmx32m -version
+  - javac -J-Xmx32m -version
 
 script:
   - admin/build.sh
@@ -25,3 +37,12 @@ notifications:
   email:
     - [email protected]
     - [email protected]
+
+before_cache:
+  - find $HOME/.sbt -name "*.lock" | xargs rm
+  - find $HOME/.ivy2/cache -name "ivydata-*.properties" | xargs rm
+cache:
+  directories:
+    - $HOME/.ivy2/cache
+    - $HOME/.sbt
+    - $HOME/.sdkman