diff --git a/Dockerfile b/Dockerfile
index df294e5..42985af 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,6 +2,8 @@
 # With thanks to David Bowes (d.h.bowes@lancaster.ac.uk) who did all the hard work
 # on this originally.
 
+# grab openjdk-16 container first, then ubuntu 20.04 base image
+FROM openjdk:16-jdk AS jdk
 FROM docker.io/ubuntu:20.04
 
 # https://github.com/opencontainers/image-spec/blob/master/annotations.md
@@ -19,8 +21,16 @@ ENV APACHE_RUN_GROUP www-data
 ENV APACHE_LOG_DIR /var/log/apache2
 ENV APACHE_LOCK_DIR /var/lock/apache2
 ENV APACHE_PID_FILE /var/run/apache2.pid
+ENV JAVA_HOME /usr/lib/jvm/java-16-openjdk-amd64
 ENV LANG C.UTF-8
 
+# Copy OpenJDK into Ubuntu container and setup via update-alternatives
+COPY --from=jdk /usr/java/openjdk-16 /usr/lib/jvm/java-16-openjdk-amd64
+RUN update-alternatives --install /usr/bin/java java /usr/lib/jvm/java-16-openjdk-amd64/bin/java 20 && \
+    update-alternatives --auto java && \
+    update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/java-16-openjdk-amd64/bin/javac 20 && \
+    update-alternatives --auto javac
+
 # Copy apache virtual host file for later use
 COPY 000-jobe.conf /
 # Copy test script
@@ -45,7 +55,6 @@ RUN ln -snf /usr/share/zoneinfo/"$TZ" /etc/localtime && \
         libapache2-mod-php \
         nodejs \
         octave \
-        openjdk-16-jdk \
         php \
         php-cli \
         php-mbstring \