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About Laszlo Csontos

Laszlo Csontos
Laszlo has been coding since the age of 9. Now he'S been coding for 25 years, with Java for 18 years and professionally for 13 years. During past projects he worked in various roles as a consultant, developer, mentor, team leader and architect. His focus areas have been database-oriented back-end applications, performance tuning techniques and distributed systems. In the last 3 years, he specialized in building microservices with the Spring Ecosystem.

Installing OpenJDK 11 on Ubuntu 18.04 for real

OpenJDK 11 was released on the 25th of September, 1018. As this is the first LTS release after version 8, it’s been awaited for long. After having it installed on Ubuntu 18.04 (Bionic Beaver), which comes with a package named openjdk-11-jdk, to my surprise that was still an earlier version (Java 10).

SRU exception for OpenJDK

The Ubuntu Foundation Team made an SRU exception for OpenJDK. Altought version 10 is a non-LTS release, they’ve packaged it as openjdk-11-jdk until OpenJDK 11 goes GA. This choice was based on that assumption that there is a much smaller interface delta between releases 10 and 11 than it would be between 8 and 11.

That’s a fairly good reasoning and perhaps an apt-get upgrade wouldn’t screw things up that badly when OpenJDK’s version gets bumped up from 10 to 11.

There’s one area tiny though where there’s a significant difference between 10 and 11 and that’s that Flight Recorder got open sourced in the meantime. OpenJDK 10 doesn’t contain flight recorder, as at that time it was a commercial feature of Oracle JDK, but OpenJDK 11 does come with it.

As a consequence, installing openjdk-11-jdk doesn’t allow applications to be instrumented with JFR, as the JVM options used to enable it simply aren’t getting recognized by OpenJDK 10. In fact, the JVM fails to start and complains about unrecognized options.

Installing Ubuntu’s default JDK

This is very simple, you just need the following package.

% apt-get install default-jdk

Nevertheless, do check what Java version does that actually install.

$ java -version
openjdk version "10.0.2" 2018-07-17
OpenJDK Runtime Environment (build 10.0.2+13-Ubuntu-1ubuntu0.18.04.2)
OpenJDK 64-Bit Server VM (build 10.0.2+13-Ubuntu-1ubuntu0.18.04.2, mixed mode)

Installing OpenJDK manually

That’s easy too, you just have to download a tarball and extract it somewhere.

% wget https://download.java.net/java/GA/jdk11/28/GPL/openjdk-11+28_linux-x64_bin.tar.gz -O /tmp/openjdk-11+28_linux-x64_bin.tar.gz
% sudo tar xfvz /tmp/openjdk-11+28_linux-x64_bin.tar.gz --directory /usr/lib/jvm
% rm -f /tmp/openjdk-11+28_linux-x64_bin.tar.gz

That’s going to be OpenJDK 11 for real.

$ /usr/lib/jvm/jdk-11/bin/java -version
openjdk version "11" 2018-09-25
OpenJDK Runtime Environment 18.9 (build 11+28)
OpenJDK 64-Bit Server VM 18.9 (build 11+28, mixed mode)

Switching between JDKs

I would prefer to use the distro’s JDK as long as it works for the task at hand. In this case, that isn’t an option, not yet at least. For that reason, I’m using the alternatives framework with which it’s possible to switch between JDKs easily.

% sudo sh -c 'for bin in /usr/lib/jvm/jdk-11/bin/*; do update-alternatives --install /usr/bin/$(basename $bin) $(basename $bin) $bin 100; done'
% sudo sh -c 'for bin in /usr/lib/jvm/jdk-11/bin/*; do update-alternatives --set $(basename $bin) $bin; done'

Once OpenJDK 11 appears in Ubuntu 18.04, it’s going to be just a matter of a package upgrade and an alternatives switch to use it.

% sudo apt-get install --only-upgrade default-jdk
% update-alternatives --config java
There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                         Priority   Status
  0            /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1101      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1101      manual mode
* 2            /usr/lib/jvm/jdk-11/bin/java                  100       manual mode

Press <enter> to keep the current choice[*], or type selection number:
Published on Java Code Geeks with permission by Laszlo Csontos, partner at our JCG program. See the original article here: Installing OpenJDK 11 on Ubuntu 18.04 for real

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