On June 3, 2019, the article posted on the company's owned media was ported. https://www.chuo-system.co.jp/csclib/

For those who "have never participated" or "want to participate but are uneasy to participate alone" ** JJUG CCC 2019 Spring ** held on Saturday, May 18, 2019 I will report what it was like.

What is JJUG?

** Japan Java User Group ** is a voluntary organization in Japan It aims to improve and develop Java technology and further spread and activate it. Japan Java User Group, ** JJUG ** for short. http://www.java-users.jp/

What is JJUG CCC?

** CCC ** stands for "Cross Community Conference" Japan's largest Java community event hosted by JJUG. It is held twice a year in spring and autumn.

Java-related sessions were held, not to mention Japanese speakers There are also overseas speakers.

The great thing about JJUG CCC

In the case of general participation frame (no social gathering), it is ** free **. Even if you have a general participation slot (with a social gathering), you can participate for ** ¥ 1,000 **.

There is a tendency for this kind of IT event to be charged a participation fee and a little expensive, At JJUG CCC, you can listen to the stories of excellent engineers regardless of country for free. ** It is a level that makes you want to say "Is it really good?" **.

On the contrary, when people say "free", they say "Is it really okay?" Isn't it a strange event? "When You may be worried, but it is sponsored by JJUG = Japan's largest Java community.

According to my research, it seems that it has been held since around 2009. We have a track record of lasting more than 10 years.

Actually ...

It was my first time to participate (low voice)

I've heard stories from senior Java engineers, If I was vaguely saying "I want to participate", 2019 has come.

Since I was recently involved in Java projects and had the opportunity to teach Java, I never applied for it, saying, "Let's jump in without saying four or five!" Participation in the general participation frame (no social gathering).

It's the day.

Somehow a fine building. Take the elevator to the 5th floor of the venue.

The reception is as shown in the image below, and it will be sent by email after applying for participation. All I had to do was read the QR code. Oh easy.

Looking around, there are by far many people who seem to be participating alone, There is no problem even for those who are not good at participating in the event alone!

In fact, a questionnaire about "which session you want to take" is taken in advance.

There are several rooms that serve as venues, and the capacities vary. Probably the management side based on the result of the preliminary questionnaire It seems that they are considering "which room should be assigned to which session". It seems that consideration is given to avoid standing as much as possible.

The passage is one-way "People who leave the room after the session" and "People who enter the room for the next session" I wasn't confused. Thanks to that, I was able to enter and leave without being rubbed by the waves.

Received session

I am not good at getting up early, so I participated in the afternoon. It doesn't mean that you have to participate all day I am grateful for the stance that it is OK to take only the session you want to take.

Getting Started: Tail Call Optimization

I recently learned about recursive functions (quiet). Participation in JJUG CCC for the first time, mysterious courage to choose for advanced players in the first session! !! The explanation from the speaker was polite, so I didn't leave it behind.

With recursive calls, the stack is piled up more and more, Therefore, stack overflow will occur. Returning the return value is "just returning", so you don't have to return each one. Shouldn't it be returned at once at the end? I was able to understand "Oh ~" from the beginning.

Mr. Miyagawa, a speaker, seems to be developing a language called Kink. Amazing (small average feeling)

Public material: https://speakerdeck.com/miyakawataku/tail-call-elimination-intro

Introduction and examples of big data processing using Apache Beam at Goldman Sachs

For some reason, I misunderstood Apache ** Beam ** as "Apache Bean = beans !?" You came from Batch + Stream (shame).

Goldman Sachs is also focusing on the IT department. I had the impression that the IT departments of non-IT companies didn't put much effort into it, but that's true.

Unfortunately, it seems that the material has not been released, so I have a link between Goldman Sachs and Apache Beam.

Goldman Sachs: https://www.goldmansachs.com/japan/
Apache Beam：https://beam.apache.org/

Spring Boot x JavaScript x IntelliJ x Agile, a modern newcomer training that I thought about with JJUG Chairman

Buzzworks (company R & D team) is in charge of training for new employees in 2019, Personally, this was my big favorite. The largest room was the venue, but it was almost full.

You said "100% promotion", but what kind of framework and software are you using? Impressions from the trainee (how much the newcomer understood, etc.), I was very happy to know the area.

And above all, the materials and the story of the speaker are good, I wanted to be like this (small average feeling part2).

Public material: https://speakerdeck.com/masatoshitada/modern-new-employees-training-spring-boot-javascript-intellij-agile

Finally

I participated in the analog style of notebook and pen, Many participants brought their own notebook PCs, and I wanted a thin notebook PC.

I was able to hear stories from people I don't usually see, The number of participants was so large that it made me feel like a festival. It was very inspiring like that. (I'm sorry for the miscellaneous impressions ...)

Since the presentation materials are also open to the public, you can see the materials of the sessions that you did not receive. I'm really grateful.

JJUG CCC 2019 Spring Presentation Material Summary: https://github.com/jjug-ccc/slides-articles-2019 Spring

I definitely want to participate in 2019 Fall! !! !!

Those who have avoided participating in JJUG CCC because they think "the threshold may be high ..." We recommend that you feel free to join us.

There is no such thing as "NG without advanced specialized knowledge and technical knowledge", We promise to inspire you!

[JAVA] I participated in JJUG CCC 2019 Spring