Thing you want to do

I want to use OpenJDK 11 on Ubuntu Linux
I want to manage packages, so I want to introduce it with ʻapt`

TL;DR update

In April 2019, OpenJDK 11 can now be installed with ʻapt` on Ubuntu Linux 18.04 LTS as well.

openjdk-lts package

After that, it will be the past information.

As of November 19, 2018, if you have Ubuntu Linux 18.10 (Cosmic), you can install OpenJDK 11 with ʻopenjdk-11-jdk`.
For Ubuntu Linux 18.04 LTS (Bionic) ...
If you don't give up installing with ʻapt`
Wait a little longer
If it's a little old, use PPA (https://launchpad.net/~openjdk-r/+archive/ubuntu/ppa?field.series_filter=bionic)
If you don't mind giving up LTS on Ubuntu Linux, upgrade to Ubuntu Linux 18.10
When giving up ʻapt`
Use other options obediently, such as sdkman and AdoptOpenJDK

Target Ubuntu Linux version

18.04 LTS or later

For Ubuntu Linux 18.10 (Cosmic)

OpenJDK 11 will be included without any problems.

##OS version
$ cat /etc/os-release 
NAME="Ubuntu"
VERSION="18.10 (Cosmic Cuttlefish)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 18.10"
VERSION_ID="18.10"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=cosmic
UBUNTU_CODENAME=cosmic


##OpenJDK 11 installation
$ sudo apt install openjdk-11-jdk
$ java -version
openjdk version "11.0.1" 2018-10-16
OpenJDK Runtime Environment (build 11.0.1+13-Ubuntu-2ubuntu1)
OpenJDK 64-Bit Server VM (build 11.0.1+13-Ubuntu-2ubuntu1, mixed mode, sharing)

Problem (for Ubuntu Linux 18.04 LTS (Bionic))

For Ubuntu Linux 18.04 LTS, if you install ʻopenjdk-11-jdk with ʻapt, you will get the following status.

##OS version
$ cat /etc/os-release 
NAME="Ubuntu"
VERSION="18.04 LTS (Bionic Beaver)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 18.04 LTS"
VERSION_ID="18.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=bionic
UBUNTU_CODENAME=bionic


##OpenJDK 11 installation
$ sudo apt install openjdk-11-jdk
$ java -version
openjdk version "10.0.2" 2018-07-17
OpenJDK Runtime Environment (build 10.0.2+13-Ubuntu-1ubuntu0.18.04.3)
OpenJDK 64-Bit Server VM (build 10.0.2+13-Ubuntu-1ubuntu0.18.04.3, mixed mode)

ʻOpenjdk-11-OpenJDK 10 is installed even though it is set to jdk`.

This is because OpenJDK 11 was not released at the time of Ubuntu Linux 18.04 LTS release, so make sure that OpenJDK 10 is the default and replace later. -release / 2018-February / 004275.html) It seems that you intend.

However, it has been a while since OpenJDK 11 was released at this point, but it seems that it is still OpenJDK 10 and has not been switched.

So, if you can't install OpenJDK 11 with ʻapt` on Ubuntu Linux 18.04 LTS, you can install it by using PPA.

“PPA for OpenJDK uploads (restricted)” team

Below, the command.

$ sudo add-apt-repository ppa:openjdk-r/ppa
$ sudo apt update
$ sudo apt install openjdk-11-jdk

It takes a lot of time, and a little old and mysterious OpenJDK 11 is installed.

$ sudo apt install openjdk-11-jdk^C
$ java -version
openjdk version "11" 2018-09-25
OpenJDK Runtime Environment (build 11+24-Ubuntu-118.04)
OpenJDK 64-Bit Server VM (build 11+24-Ubuntu-118.04, mixed mode, sharing)

At this point, if you really want to install OpenJDK 11 with ʻapt` on Ubuntu Linux 18.04 LTS, this is the way to go.

Or wait a little longer or upgrade to Ubuntu Linux 18.10.