Trying to install oracle java 8 for apache server on Ubuntu 16.04(LTS), but getting
E: Package 'oracle-java8-installer' has no installation candidate

This are my actions:

root@ubuntu-s-1vcpu-1gb-fra1-01:~# add-apt-repository ppa:webupd8team/java
 The Oracle JDK License has changed for releases starting April 16, 2019.

The new Oracle Technology Network License Agreement for Oracle Java SE is substantially different from prior Oracle JDK licenses. The new license permits certain uses, such as personal use and development use, at no cost -- but other uses authorized under prior Oracle JDK licenses may no longer be available. Please review the terms carefully before downloading and using this product. An FAQ is available here: https://www.oracle.com/technetwork/java/javase/overview/oracle-jdk-faqs.html

Oracle Java downloads now require logging in to an Oracle account to download Java updates, like the latest Oracle Java 8u211 / Java SE 8u212. Because of this I cannot update the PPA with the latest Java (and the old links were broken by Oracle).

For this reason, THIS PPA IS DISCONTINUED.

For Oracle Java 11, see a different PPA -> https://www.linuxuprising.com/2019/06/new-oracle-java-11-installer-for-ubuntu.html

That same PPA also has Oracle Java 13 -> https://www.linuxuprising.com/2019/09/install-oracle-java-13-on-ubuntu-linux.html

Old description:

Oracle Java (JDK) Installer (automatically downloads and installs Oracle JDK8). There are no actual Java files in this PPA.

Important -> Why Oracle Java 7 And 6 Installers No Longer Work: http://www.webupd8.org/2017/06/why-oracle-java-7-and-6-installers-no.html

Update: Oracle Java 9 has reached end of life: http://www.oracle.com/technetwork/java/javase/downloads/jdk9-downloads-3848520.html

The PPA supports Ubuntu 18.10, 18.04, 16.04, 14.04 and 12.04.

More info (and Ubuntu installation instructions):
- http://www.webupd8.org/2012/09/install-oracle-java-8-in-ubuntu-via-ppa.html

Debian installation instructions:
- Oracle Java 8: http://www.webupd8.org/2014/03/how-to-install-oracle-java-8-in-debian.html
 More info: https://launchpad.net/~webupd8team/+archive/ubuntu/java
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keyring `/tmp/tmpust7h62u/secring.gpg' created
gpg: keyring `/tmp/tmpust7h62u/pubring.gpg' created
gpg: requesting key EEA14886 from hkp server keyserver.ubuntu.com
gpg: /tmp/tmpust7h62u/trustdb.gpg: trustdb created
gpg: key EEA14886: public key "Launchpad VLC" imported
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
OK
root@ubuntu-s-1vcpu-1gb-fra1-01:~# apt update
Hit:1 http://ppa.launchpad.net/certbot/certbot/ubuntu xenial InRelease
Get:2 http://mirrors.digitalocean.com/ubuntu xenial InRelease [247 kB]
Hit:3 http://ppa.launchpad.net/webupd8team/java/ubuntu xenial InRelease
Hit:4 http://mirrors.digitalocean.com/ubuntu xenial-updates InRelease
Hit:5 http://mirrors.digitalocean.com/ubuntu xenial-backports InRelease
Hit:6 http://security.ubuntu.com/ubuntu xenial-security InRelease
Hit:7 https://download.jitsi.org stable/ InRelease
Fetched 247 kB in 0s (316 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
root@ubuntu-s-1vcpu-1gb-fra1-01:~# apt-get install oracle-java8-installer
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package oracle-java8-installer is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'oracle-java8-installer' has no installation candidate