update jdk8 with apt in ubuntu18

Following steps are running on a ubuntu18 server vm in pve.
And jdk8 was installed with apt previously a few years ago.

1. check current version in use
   run: java -version
   got: openjdk version "1.8.0_312"
   This version is outdated.

2. check apt source
   run:
   sudo apt update
   then:
   run: apt list | grep jdk
   this will give something like
   openjdk-8-jdk/bionic-updates,bionic-security,now 8u372-ga~us1-0ubuntu1~18.04 amd64
   followed by [upgradable from: ...]
   This is quite obvious.

3. upgrade
   run: sudo apt upgrade openjdk-8-jdk
   This may complain like:
   Could not get lock /var/lib/dpkg/lock-frontend - open
   This means some apt process is holding the lock.
   run: sudo ps -ef | grep apt to check related processes.
   If the processes in result are some background task of apt or apt-get like daily-apt, just wait for the background work to finish.
   If not, may have to kill the processes or contact server administrator.
   then:
   run: sudo apt upgrade openjdk-8-jdk

4. check again
   run: java -version
   got: openjdk version "1.8.0_362"

Done.