[Build] Revert back to OpenJDK 8

Author: mpkorstanje

.m2/travis-ci-toolchains.xml

@@ -3,11 +3,11 @@
     <toolchain>
         <type>jdk</type>
         <provides>
-            <version>11</version>
+            <version>8</version>
             <vendor>openjdk</vendor>
         </provides>
         <configuration>
-            <jdkHome>/usr/local/lib/jvm/openjdk11</jdkHome>
+            <jdkHome>/usr/lib/jvm/java-1.8.0-openjdk-amd64</jdkHome>
         </configuration>
     </toolchain>
 </toolchains>

.travis.yml

@@ -1,5 +1,5 @@
-language: java
-sudo: false
+language: scala
+os: linux
 
 cache:
   directories:
@@ -12,17 +12,20 @@ install:
 jobs:
   include:
   - stage: test
-    env: SCALA=2.11.12
+    scala:
+    - 2.11.12
     script: mvn test -pl scala/scala_2.11 -B --toolchains .m2/travis-ci-toolchains.xml
-    jdk: openjdk11
+    jdk: openjdk8
   - stage: test
-    env: SCALA=2.12.11
+    scala:
+    - 2.12.11
     script: mvn test -pl scala/scala_2.12,examples -B --toolchains .m2/travis-ci-toolchains.xml
-    jdk: openjdk11
+    jdk: openjdk8
   - stage: test
-    env: SCALA=2.13.2
+    scala:
+    - 2.13.2
     script: mvn test -pl scala/scala_2.13,examples -B --toolchains .m2/travis-ci-toolchains.xml
-    jdk: openjdk11
+    jdk: openjdk8
 
 branches:
   only:

pom.xml

@@ -30,7 +30,7 @@
         <scala.2.13.version>2.13.3</scala.2.13.version>
         <mockito-scala.version>1.14.8</mockito-scala.version>
         <toolchain.vendor>openjdk</toolchain.vendor>
-        <toolchain.java.version>11</toolchain.java.version>
+        <toolchain.java.version>8</toolchain.java.version>
     </properties>
 
     <scm>