Adopt OpenJDK & Java community: how can you help Java !


I want to take the opportunity to show what we have been doing in last year and also what we have done so far as members of the community. Unlike other years I have decided to keep this post less technical compare to the past years and compared to the other posts on Java Advent this year.


This year marks the fourth year since the first OpenJDK hackday was held in London (supported by LJC and its members) and also when the Adopt OpenJDK program was started. Four years is a small number on the face of 20 years of Java, same goes to the size of the Adopt OpenJDK community which forms a small part of the Java community (9+ million users). Although the post is non-technical in nature, the message herein is fairly important for the future growth and progress of our community and the next generation developers.

Creations of the community

Creations from the community

Over the many months a number of members of our community contributed and passed on their good work to us. In no specific order I have enlisted these picking them from memory. I know there are more to name and you can help us by sharing those with us (we will enlist them here).  So here are some of those that we can talk about and be proud of, and thank those who were involved:

  • Getting Started page – created to enabled two way communication with the members of the community, these include a mailing list, an IRC channel, a weekly newsletter, a twitter handle, among other social media channels and collaboration tools.
  • Adopt OpenJDK project: jitwatch – a great tool created by Chris Newland, its one of its kind, ever growing with features and helping developers fine-tune the performance of your Java/JVM applications running on the JVM.
  • Adopt OpenJDK: GSK – a community effort gathering knowledge and experience from hackday attendees and OpenJDK developers on how to go about with OpenJDK from building it to creating your own version of the JDK. Many JUG members have been involved in the process, and this is now a e-book available in many languages (5 languages + 2 to 3 more languages in progress).
  • Adopt OpenJDK vagrant scripts – a collection of vagrant scripts initially created by John Patrick from the LJC, later improved by the community members by adding more scripts and refactoring existing ones. Theses scripts help build OpenJDK projects in a virtualised container i.e. VirtualBox, making building, and testing OpenJDK and also running and testing Java/JVM applications much easier, reliable and in an isolated environment.
  • Adopt OpenJDK docker scripts – a collection of docker scripts created with the help of the community, this is now also receiving contributions from a number of members like Richard Kolb (SA JUG). Just like the vagrant scripts mentioned above, the docker scripts have similar goals, and need your DevOps foo!
  • Adopt OpenJDK project: mjprof – mjprof is a Monadic jstack analysis tool set. It is a fancy way to say it analyzes jstack output using a series of simple composable building blocks (monads). Many thanks to Haim Yadid for donating it to the community.
  • Adopt OpenJDK project: jcountdown – built by the community that mimics the spirit of That is, to encourage users to move to the latest and greatest Java! Many thanks to all those involved, you can already see from the commit history.
  • Adopt OpenJDK CloudBees Build Farm – thanks to the folks at CloudBees for helping us host our build farm on their CI/CD servers. This one was initially started by Martijn Verburg and later with the help of a number of JUG members have come to the point that major Java projects are built against different versions of the JDK. These projects include building the JDKs themselves (versions 1.7, 1.8, 1.9, Jigsaw and Shenandoah). This project has also helped support the Testing Java Early project and Quality  Outreach program.

These are just a handful of such creations and contributions from the members of the community, some of these projects would certainly need help from you. As a community one more thing we could do well is celebrate our victories and successes, and especially credit those that have been involved whether as individuals or a community. So that our next generation contributors feel inspired and encourage to do more good work and share it with us.

Contributions from the community

We want to contribute

In a recent tweet and posts to various Java / JVM and developer mailing lists, I requested the community to come forward and share their contribution stories or those from others with our community. The purpose was two-fold, one to share it with the community and the other to write this post (which in turn is shared with the community). I was happy to see a handful of messages sent to me and the mailing lists by a number of community members. I’ll share some of these with you (in the order I have received them).

Sebastian Daschner:

I don’t know if that counts as contribution but I’ve hacked on the
OpenJDK compiler for fun several times. For example I added a new
thought up ‘maybe’ keyword which produces randomly executed code:

Thomas Modeneis:

Thanks for writing, I like your initiative, its really good to show how people are doing and what they have been focusing on. Great idea.
From my part, I can tell about the DevoxxMA last month, I did a talk on the Hacker Space about the Adopt the OpenJDK and it was really great. We had about 30 or more attendees, it was in a open space so everyone that was going to any talk was passing and being grabbed to have a look about the topic, it was really challenging because I had no mic. but I managed to speak out loud and be listen, and I got great feedback after the session. I’m going to work over the weekend to upload the presentation and the recorded video and I will be posting here as soon as I have it done! 🙂

Martijn Verburg:

Good initiative.  So the major items I participated in were Date and Time and Lambdas Hackdays (reporting several bugs), submitted some warnings cleanups for OpenJDK.  Gave ~10 pages of feedback for jshell and generally tried to encourage people more capable than me to contribute :-).

Andrii Rodionov:

Olena Syrota and Oleg Tsal-Tsalko from Ukraine JUG: Contributing to JSR 367 test code-base (, promoting ‘Adopt a JSR’ and JSON-B spec at JUG UA meetings ( and also at JavaDay Lviv conference (


Contributors gathering together

As you have seen that from out of a community of 9+ million users, only a handful of them came forward to share their stories. While I can point you out to another list of contributors who have been paramount with their contributions to the Adopt OpenJDK GitBook, for example, take a look at the list of contributors and also the committers on the git-repo. They have not just contributed to the book but to Java and the OpenJDK community, especially those who have helped translate the book into multiple languages. And then there are a number of them who haven’t come forward to add their names to the list, even though they have made valuable contributions.
Super heroes together

From this I can say contributors can be like unsung heroes, either due their shy or low-profile nature or they just don’t get noticed by us. So it would only be fair to encourage them to come forward or share with the community about their contributions, however simple or small those may be. In addition to the above list I would like to also add a number of them (again apologies if I have missed out your name or not mentioned about you or all your contributions). These names are in no particular order but as they come to my mind as their contributions have been invaluable:

  • Dalibor Topic (OpenJDK Project Lead) & the OpenJDK team
  • Mario Torre & the RedHat OpenJDK team
  • Tori Wieldt (Java Community manager) and her team
  • Heather Vancura & the JCP team
  • NightHacking, vJUG and RebelLabs (and the great people behind them)
  • Nicolaas & the team at Cloudbees
  • Chris Newland (JitWatch developer)
  • Lucy Carey, Ellie & Mark Hazell (Devoxx UK & Voxxed)
  • Richard Kolb (JUG South Africa)
  • Daniel Bryant, Richard Warburton, Ben Evans, and a number of others from LJC
  • Members of SouJava (Otavio, Thomas, Bruno, and others)
  • Members of Bulgarian JUG (Ivan, Martin, Mitri) and neighbours
  • Oti, Ludovic & Patrick Reinhart
  • and a number of other contributors who for some reason I can’t remember…

I have named them for their contributions to the community by helping organise Hackdays during the week and weekends, workshops and hands-on sessions at conferences, giving lightening talks, speaking at conferences, allowing us to host our CI and build farm servers, travelling to different parts of the world holding the Java community flag, writing books, giving Java and advance-level training, giving feedback on new technologies and features, and innumerable other activities that support and push forward the Java / JVM platform.

How you can make a difference ? And why ?

Make a difference

You can make a difference by doing something as simple as clicking the like button (on Twitter, LinkedIn, Facebook, etc…) or responding to a message on a mailing list by expressing your opinion about something you see or read about –as to why you think about it that way or how it could be different.

The answer to the question “And why ?” is simple, because you are part of a community and ‘you care’ and want to share your knowledge and experience with others — just like the others above who have spared free moments of their valuable time for us.

Is it hard to do it ? Where to start ? What needs most attention ?

important-checklist The answer is its not hard to do it, if so many have done it, you can do it as well. Where to start and what can you do ? I have written a page on this topic. And its worth reading it before going any further.

There is a dynamic list of topics that is worth considering when thinking of contributing to OpenJDK and Java. But recently I have filtered this list down to a few topics (in order of precedence):

We need you!

With that I would like to close by saying:


Not just “I”, but we as a community need you.

This post is part of the Java Advent Calendar and is licensed under the Creative Commons 3.0 Attribution license. If you like it, please spread the word by sharing, tweeting, FB, G+ and so on!

Effective UI tests with Selenide

Waiting for miracles

Christmas is a time for miracles. On the eve of the new year we all build plans for the next. And we hope that all problems will leave in the ending year, and a miracle happens in the coming year.

Every Java developer dreams about a miracle that lets him become The Most Effective Java Developer in the world.

I want to show you such a miracle.

It’s called automated tests!

Ugh, tests?

Yes. You will not become a real master thanks to micro/pico/nano services. You will become a real master thanks to discipline. Discipline claiming that developer only then reports jobs as donewhen code and tests are written and run.

But, isn’t testing boring?

Oh no, believe me! Writing of fast and stable automated tests is a great challenge for smartest heads. And it can be very fun and interesting. You only need to use right tools.

The right tool for writing UI tests is:


Selenide is an open-source library for writing concise and stable UI tests.

Selenide is an ideal choice for software developers because it has a very low learning curve. Thus, you don’t need to bother with browser details, all these typical ajax and time issues that eat most of QA automation engineers’ time.

Let’s look at a simplest Selenide test:

public class GoogleTest {
  public void user_can_search_everything_in_google() {

    $$("#ires .g").shouldHave(size(10));

    $("#ires .g").shouldBe(visible).shouldHave(
        text("Selenide: concise UI tests in Java"),

Let’s look closer what happens here.

  • You open a browser with just one command open(url)
  • You find an element on a page with command $.
    You can find element by name, ID, CSS selector, attributes, xpath and even by text.
  • You manipulate the element: enter some text with val() and press enter with (surprise-surprise!) pressEnter().
  • You check the results: find all found results with $$ (it returns a collection of all matched elements). You check the size and content of the collection.

Isn’t this test easy to read? Isn’t this test easy to write?

I believe it is.

Deeper into details

Ajax/timing problems

Nowdays web applications are dynamic. Every single piece of application can be rendered/changed dynamically at any moment. This creates a lot of problems for automated tests. Test that is green today can suddenly become red at any moment, just because browser executed some javascript a little bit longer than usual.

It’s a real pain in the ajjaxx.

Quite unbelievably, but Selenide resolves most of the these problems in a very simple way.

Simply said, every Selenide method waits a little bit if needed. People call it “smart waiting”.

When you write


Selenide checks if the element exists and contains text “Hello”.

If not yet, Selenide assumes that probably the element will be updated dynamically soon, and waits a little bit until it happens. The default timeout is 4 seconds, which is typically enough for most web applications. And of course, it’s configurable.

Rich set of matchers

You can check pretty much everything with Selenide. Using “smart waiting” mechanism mentioned above.

For example, you can check if element exists. If not yet, Selenide will wait up to 4 seconds.


You can even check that element does not exist. If it still exists, Selenide will wait up to 4 seconds until it disappears.


And you can use fluent API and chain methods to make your tests really concise:

  .shouldHave(text("Hello"), text("John!"))
  .shouldBe(enabled, selected);


Selenide allows you to work with collections, thus checking a lot of elements with one line of code.

For example, you can check that there are exactly N elements on a page:


You can find subset of collections:

$$("#employees tbody tr")

You can check texts of elements. In most cases, it’s sufficient to check the whole table or table row:

$$("#employees tbody tr").shouldHave(
      "John Belushi",
      "Bruce Willis",
      "John Malkovich"

Upload/download files

It’s pretty easy to upload a file with Selenide:

$("#cv").uploadFile(new File("cv.doc"));

You can even upload multiple files at once:

  new File("cv1.doc"),
  new File("cv2.doc"),
  new File("cv3.doc")

And it’s unbelievably simple to download a file:

File pdf = $(".btn#cv").download();

Testing “highly dynamic” web applications

Some web frameworks (e.g. GWT) generate HTML that is absolutely unreadable. Elements do not have constant IDs or names.

It’s a real pain in the xpathh.

Selenide suggests to resolve this problem by searching elements by text.

import static com.codeborne.selenide.Selectors.*;

$(byText("Hello, Devoxx!"))     // find by the whole text

$(withText("oxx"))              // find by substring
   .shouldHave(text("Hello, Devoxx!"));

Searching by text is not bad idea at all. In fact, I like it because it emulates behaviour of real user. Real user doesn’t find buttons by ID or XPATH – he finds by text (or, well, color).

Another useful set of Selenide methods allows you to navigate between parents and children.


For example, you can find a table cell by text, then by its closest tr descendant and find a “Save” button inside this table row:


… And many other functions

Selenide has many more functions, like:


but the good news is that you don’t need to remember all this stuff. Just put $, put dot and choose from available options suggested by your IDE.

Use the power of IDE! Concentrate on business logic.

Power of IDE

Make the world better

I believe the World will get better when all developers start writing automated tests for their code. When developers will get up at 17:00 and go to their children without fearing that they broke something with last changes.

Let’s make the world better by writing automated tests!

Deliver working software.

Andrei Solntsev