Require at least JDK 11 for the build

.appveyor.yml

@@ -7,7 +7,8 @@ install:
       curl -LsS "http://www.apache.org/dyn/closer.cgi?action=download&filename=maven/maven-3/3.3.9/binaries/apache-maven-3.3.9-bin.zip" > apache-maven-3.3.9-bin.zip &&
       unzip apache-maven-3.3.9-bin.zip -d C:\Users\appveyor
     )
-  - SET PATH=C:\Users\appveyor\apache-maven-3.3.9\bin;%PATH%
+  - SET JAVA_HOME=C:\Program Files\Java\jdk11
+  - SET PATH=C:\Users\appveyor\apache-maven-3.3.9\bin;%JAVA_HOME%;%PATH%
 
 build_script:
   # Maven 3.3.9 requires Java >= 7, but generation of Javadocs requires Java <= 6 (https://github.com/jacoco/jacoco/issues/110)

.azure-pipelines/azure-pipelines.yml

@@ -78,7 +78,7 @@ jobs:
       tar -xzf .maven/maven.tar.gz -C .maven --strip-components 1
     displayName: Setup Maven
   - bash: |
-      if [[ "$JDK_VERSION" -ge "8" ]]; then
+      if [[ "$JDK_VERSION" -ge "11" ]]; then
         export JAVA_HOME=$PWD/.jdk
       fi
       if [[ "$BUILD_SOURCEBRANCH" == "refs/heads/master" && "$JDK_VERSION" == "5" ]]; then

org.jacoco.build/pom.xml

@@ -531,7 +531,7 @@
             <configuration>
               <rules>
                 <requireJavaVersion>
-                  <version>1.8</version>
+                  <version>11</version>
                 </requireJavaVersion>
                 <requireMavenVersion>
                   <!-- Maven 3.8.2 contains bug - see https://github.com/jacoco/jacoco/issues/1218 -->

org.jacoco.doc/docroot/doc/build.html

@@ -24,7 +24,7 @@ <h1>Build</h1>
   The JaCoCo build is based on <a href="http://maven.apache.org/">Maven</a> and
   can be locally executed on every machine with a proper
   <a href="environment.html">environment setup</a>. In particular you need at
-  least <a href="http://maven.apache.org/">Maven 3.3.9</a> and JDK 8
+  least <a href="http://maven.apache.org/">Maven 3.3.9</a> and JDK 11
   installations. Developers are encouraged to run the build before every commit
   to ensure consistency of the source tree.
 </p>