title: Install Java runtime in Debian based docker image
body: <p>I am trying to install the java runtime in a Debian based docker image (mcr.microsoft.com/dotnet/core/sdk:3.1-buster). According to various howtos this should be possible by running</p>
  
  <pre><code>RUN apt update
  RUN apt-get install openjdk-11-jre
  </code></pre>
  
  <p>The latter command comes back with </p>
  
  <pre><code>E: Unable to locate package openjdk-11-jre
  </code></pre>
  
  <p>However according to <a href="https://packages.debian.org/buster/openjdk-11-jre" rel="noreferrer">https://packages.debian.org/buster/openjdk-11-jre</a> the package does exist. What am I doing wrong?</p>