You can’t ignore the issue...
There are however a couple of ways to fix it.
You can upgrade to Debian 10: this currently has a version of OpenJDK close to that in unstable, and will soon have exactly the same.
You can install OpenJDK (11) from Stretch backports; this is identical to the version in unstable, but built against Stretch’s packages.
The latter is probably the simpler:
echo deb http://deb.debian.org/debian stretch-backports main | sudo tee /etc/apt/sources.list.d/stretch-backports.list
sudo apt update
sudo apt install -t stretch-backports openjdk-11-jdk
You might still have to deal with some fallout from your libc discrepancies, but the details there depend on exactly what you upgraded along with OpenJDK.
You can have OpenJDK 8 and 11 installed in parallel in this fashion, and use whichever is appropriate by setting
JAVA_HOME accordingly. The system-wide default version of Java can be set by running
To install older versions of Java, you can try installing package sets from Debian snapshots; you’ll find OpenJDK 6 and OpenJDK 7. I wouldn’t try versions 9 and 10, because they were never released in a stable distribution; they shouldn’t be needed anyway.
Whatever you do, don’t try installing packages from newer releases of Debian, and don’t use