It's rare, but people ask what is jPrime. Well here's the just of it:
jPrime is a community driven technology conference organized once a year by the Bulgarian JUG in Sofia, Bulgaria. Obviously it focuses on the world of Java.
Surrender your ego
It's rare, but people ask what is jPrime. Well here's the just of it:
jPrime is a community driven technology conference organized once a year by the Bulgarian JUG in Sofia, Bulgaria. Obviously it focuses on the world of Java.
Antoine spent a while day with us explaining CDI 1.2 and the upcoming 2.0. We discussed CDI extensions and he wrote some live code.
Links:
These are the slides from the last session. The most interesting part.
I did a short presetation on JShell - Java9's new REPL environment.
Here's the video (in Bulgarian)
Here's the code for nashorn:
import java.net.http.*; import java.util.stream.* import javax.script.* // URL to fetch JSON for weather data for Pravets, Bulgaria String url = "http://api.openweathermap.org/data/2.5//forecast/daily?q=Pravets,BG&appid=27fc9aa7cc0af902105a9c4c2d97845c&mode=json&units=metric&cnt=7"; //java 9 http api String json = HttpRequest.create(new URI(url)).GET().response().body(HttpResponse.asString()) // create nashorn engine ScriptEngine e = new ScriptEngineManager().getEngineByName("js") // expose weather data JSON as global variable to nashorn engine e.put("str", json) // massage JSON using nashorn and get the max. temp values double[] values = (double[]) e.eval("Java.to(JSON.parse(str).list.map(function(val) val.temp.max), Java.type('double[]'))") printf(Arrays.toString(values)+"\n") // stat on max. temp values printf(DoubleStream.of(values).summaryStatistics().toString()) |
Usually I do the review of what we do in our JUG, but Dmitry did quite a good job and he has the best pictures.
Some minor additions from me:
Venkat Subramaniam also known simply as Venkat was here. Venkat is a rockstar (JavaOne Rockstar is someone who did an amazing session at JavaOne. Venkat is 16 (sixteen!!!) times J1 Rockstar in just 4 years).
Venkat did two sessions and a workshop. The two sessions (one on lambdas and one soft-code session on bad code) were highly popular, probably 150-200 people came.
Then there was a workshop that turned into a discussion on lambdas and quality code in general. Which was awesome.
More info on the event page in facebook and on our jProfessionals social page. Photo album.
Some highlights:
I have JDK8 and JDK9. I mostly use JDK8 for new projects. But all new projects are with JDK9 and with language level 6
How do I fix the default settings:
Go to File -> Other Settings -> Default Project Structure and then change them.
JRE for browsers (mine was 1.8.0_101, 160mb, was up to date):
/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/bin/java
JDK, JRE installed with installer:
/Library/Java/JavaVirtualMachines/
I had only:
$ du -d1 -h
312M ./jdk1.8.0_25.jdk
Was not up to date.
After installing U101, I had:
$ du -d1 -h
338M ./jdk1.8.0_101.jdk
312M ./jdk1.8.0_25.jdk
I removed the old one.
journalctl --vacuum-size=100M #remove all logs, only retain 100mb pacman -Scc #remove all package installation files (obsolete and current) pacman -S bleachbit bleachbit -c system.*
du -d1 -h / 2>/dev/null | sort -h
This shows a sorted list of the largest dirs in `/`
You can do two levels down:
du -d2 -h / 2>/dev/null | sort -h
My result is:
0 /proc 0 /sys 0 /tmp 12K /dev 12K /srv 16K /lost+found 632K /run 4.3M /boot 13M /opt 15M /etc 75M /root 93M /home 2.4G /var 3.2G /usr 221G /mnt 227G /
I ignore /mnt
(because that's an external drive)
Two dirs stand to mind: var
and usr
.
Let's see what's inside:
du -d1 -h /var /usr 2>/dev/null | sort -h
Then, a little bit deeper:
du -d1 -h /var/log /usr/share /usr/lib /var/cache 2>/dev/null | sort -h
I have 717mb in /var/log
.
I'm not a fan of deleting directories randomly, so let's do it the clean way:
$ journalctl --disk-usage Archived and active journals take up 728.7M on disk.
Let's leave only 100mb of logs:
journalctl --vacuum-size=100M ... Deleted archived journal /var/log/journal/ba5391...b.journal (8.0M). ... Vacuuming done, freed 616.6M of archived journals on disk.
More info here on how to configure journalctl here.
I have 660M /var/cache/pacman
. It was 1.8gb, but I ran pacman -Sc
to remove unused packages. Let's remove the rest:
pacman -Scc
A lot of users do remove it, or at least clean it up. But I might be a problem. But checkout bleachbit (next paragraph).
Automatic cleaner. Will delete a lot of stuff, but for it was mostly locales.
$ pacman -S bleachbit $ bleachbit -p system.* Disk space to be recovered: 488.8MB $ bleachbit -c system.*
You can look for more stuff to delete:
bleachbit --list bleachbit -p thunderbird.*
I need a new router, because the time machine I have been using for so long is finally giving up. It was a pretty strong machine. God bless her soul. Now I'd like to have something like this as a router:
https://www.solid-run.com/product/clearfog-pro/ But that's pricey and needlessly powerful, it costs extra to add wifi, box, power and so on.
Since I found out OpenWRT exists I have continuously rooted my routers. OpenWrt is minimalistic linux made especially for routers. I don't like the fact that it's not a full-fledged linux - they had to minimize the footprint and some packages are incomplete/different. But it does its jobs perfectly.
There is a hardware compatibility list which now features devices with 1gb ram and 4gb flash. Unfortunately they either have no wifi, or not enough lan ports. Even the Bulgarian producer Olimex is featured close to the top.
Starting from top to bottom, here's how I chose my router:
(I skip all that have no wifi)
Possibilities (all of them are available in local shops):
(all of them support some type of ac on 5Ghz)
In the table I didn't put CPU type and whether they have USB 2/3 ports.
Some mainboards won't boot without an active graphics chip which in turn won't start without a monitor connected.
This hack works with 3 resistors (75 ohm (50-150 is fine), 0.25 watt (0.125-0.500 watt is fine)).
Resources:
https://www.techpowerup.com/forums/threads/how-to-make-a-dummy-vga-dongle.86507/
http://www.geeks3d.com/20091230/vga-hack-how-to-make-a-vga-dummy-plug/
http://www.electronics-lab.com/how-to-make-a-vga-dummy-plug/
I did a talk on Jigsaw at BGOUG.
The talk is for a very important new feature in Java SE 9. Code named Jigsaw, this feature modularizes the Java SE platform.
The coolest thing I do at the talk is to create a custom JRE.
Of course the jug and jPrime were mentioned.
Code: https://bitbucket.org/stybz/jigsaw.sty/src/
Video:
Presentation:
There's a column on the Bulgarian JUG at:
http://www.javamagazine.mozaicreader.com/MarApr2016/Default/19/
(It's very annoying that you have to login)
Today we had a session by Christoph Engelbert on jCache (and hazelcast). He was forced to wear our official jug.bg wear:
Then we had a hands-on-lab (link to be added later) created by Ivan.
It was pretty awesome
So I'll do a talk about Http/2.0 at Riga Dev Day Conference. I'll be there representing the jug.bg. I'm pretty psyched to check out Latvia.
My session is on the first day
Update: my talk didn't go too well, because of projector issues. 15 min gone, flickering screen and me nervous ... overshot my time.
And to top it all of they recorded it and said it will go to youtube in a couple of months. 🙁
Not that it matters, but all my demos worked, kind of a Pyrrhic victory.
Update2: Riga is awesome and very beautiful.
Today Oleg presented a very interesting session about how class loaders work. He even remotely loaded classes from images (I imagine steganography).
Oleg works for Zero Turnaround, the company behind jRebel. Code examples here. The presentation is here.
One of the most interesting sessions so far IMHO.
A bit of introduction - we as a jug (java user group) got more active at the end of 2013 in no small part thanks to Ivan. We managed to build openjdk, import it in 3 major IDEs (eclipse, intellij and netbeans) and contributed a Virtual Machine with buildable openjdk 9 (both in fedora and ubuntu) and organized a couple of events, we decided we were ready for the next part.
At the end of 2014 we started timidly to try to contribute in the Adopt OpenJDK program. Adopt OpenJDK allows everyone* to participate in building and writing the java platform itself (or at least that's how we understood it *back then*).
We knew that LJC (London Java Community - their most popular jug) heavily participated in the new Date/Time API and soujava (Brasil's most popular jug) also managed to include code in the OpenJDK. Elated by these guys' successes we decided we had enough free time and sheer energy to contribute to the OpenJDK and thus put ourselves on the OpenJDK map.
In December 2014 we asked for something to work on. Nobody answered.
We decided to work on a simple Throwable convenience method (JDK-5050783). We had a hackaton. We submitted our fix. We were given some feedback and we submitted another. And we were told not to play with grown up stuff. That was a bit discouraging. But we didn't give up.
In February 2015 we started working on jaxp warnings. We fixed 43 easy warnings and submitted a patch. Then we fixed more harder warnings and submitted another patch. The great Joe Darcy answered but unfortunately we got nowhere again. That sucks.
A bit before that (Dec 2014) jug.bg member Doychin Bonzhev found a bug in the NetworkInterface and submitted a solution. He even submitted to another mail-list. He got a response (saying it is reasonable solution) and answered, but that was it. Nothing AFAIK followed.
So that was it for us. We gave up. Probably we didn't know the right people, but I argue that shouldn't matter. From time to time we get mentioned as collaborators in the Adopt OpenJDK by our dear friend Mani. We don't feel like that at all.
* Now you understand why the asterisk, right?
Today was the second edition of the jProfessionals format we started 5 months ago.
jProfessionals is a one-day free conf. Smaller than jPrime (our star yearly event).
In the first version we invited Koshuke Kawaguchi. (the creator of Jenkins CI).
Today the first presenter was Richard Warburton.
The session was about java 8 lambdas and even though it started as a very introductory session it turned out to be quite interesting. We discussed currying, Optional and the elvis operator.
What I learned is that Optional with value types is going to be fast (all in stack, no heap). Elvis is going in another direction - just a simple !=null check. Optional is kind of an explicit contract (preferred despite the verbosity and the extra object).
The second speaker was Vlado Tsanev aka tsachev.
He talked about Spring REST Docs. The talk was one big live demo. REST Docs is a way to document a rest api automatically by extracting the info from the tests - it creates cURL commands, headers, params as so called snippets, and it allows the use of a adoc files with links to the REST Docs snippets.
After a tasty lunch it was time for "The Seven Deadly Sins of Microservices" by Daniel Bryant.
It was a soft session with a lot of links and cool ideas of what microservices are good for and what they are not. There was a discussion on where people fail mostly using them. Very interesting and engaging - I bookmarked a lot of books that I'm never going to read.
Doychin Bondzev talked about Firebird (an alternative to postgres) - free, has triggers and is embeddable with nice tools and binary backup that is fast enough on windows.
Richard Warburton was next with another session for the future of Generics which was really fun.
I finally understood why enums are defined recursively (Enum<E extends Enum<E>>).
Next was a talk about Jenkins Builds with Docker Containers by Petar Velikov from e-card.bg.
It was quite interesting especially the docker part (he even used dockviz).
Finally there were two lightning talks. Martin Toshev talked about RxJava and RxJS.
Another guy - Teodor Tunev talked about Activiti - a java BPM platform far better than jBPM in his words.
Finally some beer was due.
(has not arrived yet)
My first fosdem this year. I found a lot of interesting things mostly on the opensource tracks. The "free java" track IMHO was a bit unpopular even though Stephen Chin and Mark Reinhold were there.
I guess I'm used to a better treatment on a conference (I go mostly as a speaker). Here it was rainy and cold and even though the french fries were awesome, I'm used to better food.
Antoan presented a session about Spring Boot running on Docker and how to use the docker maven plugin inside a Spring Boot application.
Actually we talked mostly about running Docker and application from the ecosystem. There was a statement that uninstalling Kitematic requires payment, which started a discussion about this model.
Today we had a meeting that discussed a way to automate deployments on AWS.
SDL's Behrooz Nobakht came especially for our event to explain how that is automated within their own products.
The first edition of jProfessionals is happening right now.
We managed to bring over Koshuke Kawaguchi. He's the creator of Hudson and after leaving Oracle, creator of the open source Jenkins. The topic was Jenkins 2.0.
The next speaker is Vladimir Tsanev. He'll talk about JMH with examples. Very interesting topic. He actually showed how to create a simple benchmark and to how to execute it.
Update: After the plentiful lunch Svetlin Nakov was awesome presenting HTTP/2. He was great at explaining the inner workings of the new protocol. Emil Doychev presented Groovy. There was a little bashing on JPA.
Some time for coffee and Doychin Bondzhev presented JavaFX in a very accessible way.
Trayan Iliev talked about high performance reactive programming with java 8. It was very interesting. Especially the demo at the end.
Wow.
Writing this I'm listening to Alan Bateman and Mark Reinhold deliver a session on the new Jigsaw (their third attempt?). This time it might work.
There's a lot of beer, more than I can handle (it turns out that a teenage girl handles her liquor better than I can) . A lot of awesome sessions - even one on the history of the universe.
The JUG is represented by Ivan, Krasi, Vladi and a bunch more awesome folks that make my trip here awesome.
I did a session at 2015.java2days.com about http/2.
Slides:
For more questions, use the comments section.
It was a surprise to me, but I got invited to a forum organized by HP to explain to young women that a career in IT is not scary, doesn't suck at all and why it might be something that they may enjoy.
There were around 50 guests.
I was invited as an example of a "young" "successful" person. It was an honor sitting next to the Iravan Hira (CEO of HP Bulgaria), Preslav Pavlov (Global Deliveries Director for HP), Rumyana Trencheva (CEO of SAP Bulgaria), Zornica Iankova (HP's HR Director), Kristina Stoitsova (R&D at VMware).
Modrator was webcafe.bg's owner Sibina Grigorova.
The event was highly entertaining for me. The public initially wasn't keen on asking too many questions. But the discussion afterwards proved interesting. I was happy to hear that female CEOs didn't feel male colleagues treated them differently. Still there are far more males than females in IT.
Of course I wore a @bgjug t-shirt.
Jug.mk's leader Pance Cavkovski is talking today about how to put java on a raspberry pi and then automate your home.
There is also a slide about NodeMCU that helps you distribute GPIO around your home and control different devices. NodeMCU is a wifi-to-GPIO for $5 basically, which is awesome:
Today was a busy day, the beer was over in seconds and that sucks because Ivan and I only had a beer.
I brought a Odroid C1. But pi4j doesn't work, so I used jOdro.
We have a new banner that we didn't forget to bring today, so there it is:
On 30.09.2015 we did a workshop that showcased the very beta of MVC 1.0 implemented in ozark.
We had to use glassfish, which I somehow dislike, because I don't understand it and it didn't run very smooth, but in glassfish's defense I have to say that reloading the application without restarting worked like a charm. That is awesome.
MVC is promising and I like how simple it is.
The code is here: https://github.com/bgjug/mvc10-workshop.
It’s possible that some users may even find that the HTTPS version of a web site is faster than HTTP. This can happen if they sit behind a coporate HTTP proxy that normal intercepts, examines and records web traffic. An HTTPS connection will often just be forwarded as a simple TCP connection through the proxy because HTTPS traffic cannot be intercepted. It’s this bypassing that can lead to improved performance.
Source: http://blog.httpwatch.com/2011/01/28/top-7-myths-about-https/
I can actually confirm this to be true in some cases. Even worse is that people might think that HTTPS prevents corporate from sniffing - that is not always the case 🙂
So this weekend the Bulgarian Java User Group (jug.bg) organized a hackaton to try to create a JBoss Forge plugin to create Spring Boot applications.
JBoss Forge is a tool to ease development. Main traits are it can create JPA entities, It can create an example REST interface to those entities, a web interface to those entities and it integrates with Eclipse and IntelliJ IDEA:
The code is here. Here are a couple of pictures from the event:
My WordPress installation's CPU started gradually spiking. Using P3, I found out that a stat plugin was abusing my installation
Before deinstallation:
After removing pixelstats:
I saved almost a second on initial load. How have I lived like this for so long?
The last day of jCrete was with two hacking sessions - one on optimizing a NES emulator (if I got it correctly) and one on building a Lego and writing some software on LeJOS and EV3 controller (ARM processor inside).
This is what we did (@claudiotagliola did more than I have):
We used LeJOS, with LeJOS plugin for eclipse, initial code we got from Steven's presentation on the subject, but we decided not to build the thing shown on the presentation.
We built a pretty bulky two-motor lego using snow-chains. We installed a server app that listened on a port and we sent it commands using a awt/swing app.
The app installed on the device:
package jcrete.hacking;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import lejos.hardware.Button;
import lejos.hardware.Key;
import lejos.hardware.KeyListener;
import lejos.hardware.motor.EV3LargeRegulatedMotor;
import lejos.hardware.port.MotorPort;
import lejos.utility.Delay;
/**
* This was written on jCrete 2015 on a LeJOS session by Steven Chin.
*
* We were given the task to build a lego and do something cool with it.
* We built a pretty large tank and remote-controlled it via wi-fi with
* simple socket commands.
*
* For more info, go to https://mihail.stoynov.com/?p=2909
*
* This is a mock server for testing if you don't have a lego at hand.
*
* @author Nayden Gochev, jug.bg
* @author Mihail Stoynov, jug.bg
*
*/
public class E3vRemoteControlCarApp {
static boolean isRunning = true;
public static void main(String[] args) throws IOException {
try (
final EV3LargeRegulatedMotor leftMottor = new EV3LargeRegulatedMotor(MotorPort.B);
final EV3LargeRegulatedMotor rightMottor = new EV3LargeRegulatedMotor(MotorPort.C);
ServerSocket serv = new ServerSocket(19231);
) {
Socket socket = serv.accept();
BufferedReader reader = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
// if we use the buttons on the device directly
Button.UP.addKeyListener(new KeyListener() {
@Override
public void keyReleased(Key k) {
leftMottor.stop(true);
rightMottor.stop(true);
}
@Override
public void keyPressed(Key k) {
leftMottor.setSpeed(1500);
leftMottor.setAcceleration(150);
leftMottor.forward();
rightMottor.setSpeed(1500);
rightMottor.setAcceleration(150);
rightMottor.forward();
}
});
Button.DOWN.addKeyListener(new KeyListener() {
@Override
public void keyReleased(Key k) {
leftMottor.stop(true);
rightMottor.stop(true);
}
@Override
public void keyPressed(Key k) {
leftMottor.setSpeed(1500);
leftMottor.setAcceleration(150);
leftMottor.backward();
rightMottor.setSpeed(1500);
rightMottor.setAcceleration(150);
rightMottor.backward();
}
});
Button.RIGHT.addKeyListener(new KeyListener() {
@Override
public void keyReleased(Key k) {
rightMottor.stop(true);
leftMottor.stop(true);
}
@Override
public void keyPressed(Key k) {
rightMottor.setSpeed(1500);
rightMottor.setAcceleration(150);
rightMottor.forward();
leftMottor.setSpeed(1500);
leftMottor.setAcceleration(150);
leftMottor.backward();
}
});
Button.LEFT.addKeyListener(new KeyListener() {
@Override
public void keyReleased(Key k) {
rightMottor.stop(true);
leftMottor.stop(true);
}
@Override
public void keyPressed(Key k) {
rightMottor.setSpeed(1500);
rightMottor.setAcceleration(150);
rightMottor.backward();
leftMottor.setSpeed(1500);
leftMottor.setAcceleration(150);
leftMottor.forward();
}
});
Button.ESCAPE.addKeyListener(new KeyListener() {
@Override
public void keyReleased(Key k) {
}
@Override
public void keyPressed(Key k) {
E3vRemoteControlCarApp.isRunning = false;
}
});
// we copied it from somewhere, not necessary
Delay.msDelay(3000);
// the listener with the while readline
String line;
while ((line = reader.readLine()) != "STOP" && isRunning) {
System.out.println("RECIEVED " + line);
switch (line) {
case "UP-PRESS":
leftMottor.setSpeed(1500);
// leftMottor.setAcceleration(150);
leftMottor.forward();
rightMottor.setSpeed(1500);
// rightMottor.setAcceleration(150);
rightMottor.forward();
break;
case "UP-RELEASE":
leftMottor.stop(true);
rightMottor.stop(true);
break;
case "DOWN-PRESS":
leftMottor.setSpeed(1500);
// leftMottor.setAcceleration(150);
leftMottor.backward();
rightMottor.setSpeed(1500);
// rightMottor.setAcceleration(150);
rightMottor.backward();
break;
case "DOWN-RELEASE":
leftMottor.stop(true);
rightMottor.stop(true);
break;
case "LEFT-PRESS":
rightMottor.setSpeed(1500);
// rightMottor.setAcceleration(150);
rightMottor.backward();
leftMottor.setSpeed(1500);
// leftMottor.setAcceleration(150);
leftMottor.forward();
break;
case "LEFT-RELEASE":
rightMottor.stop(true);
leftMottor.stop(true);
break;
case "RIGHT-PRESS":
rightMottor.setSpeed(1500);
// rightMottor.setAcceleration(150);
rightMottor.forward();
leftMottor.setSpeed(1500);
// leftMottor.setAcceleration(150);
leftMottor.backward();
break;
case "RIGHT-RELEASE":
rightMottor.stop(true);
leftMottor.stop(true);
break;
case "STOP":
E3vRemoteControlCarApp.isRunning = false;
break;
}
}
}
}
}
The controller:
import java.awt.BorderLayout; import java.awt.event.KeyEvent; import java.awt.event.KeyListener; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import java.io.BufferedWriter; import java.io.IOException; import java.io.OutputStreamWriter; import java.net.Socket; import java.net.UnknownHostException; import javax.swing.JButton; import javax.swing.JFrame; /** /** * This was written on jCrete 2015 on a LeJOS session by Steven Chin. * * We were given the task to build a lego and do something cool with it. * We built a pretty large tank and remote-controlled it via wi-fi with * simple socket commands. * * For more info, go to https://mihail.stoynov.com/?p=2909 * * This is a mock server for testing if you don't have a lego at hand. * * @author Nayden Gochev, jug.bg * @author Mihail Stoynov, jug.bg * */ public class Remote extends JFrame { private static final long serialVersionUID = -8402983606638099877L; private final JButton left; private final JButton right; private final JButton up; private final JButton down; private final JButton stop; private BufferedWriter pw; public static void main(String[] args) { Remote remote = new Remote(); remote.setSize(500, 500); remote.setVisible(true); } public Remote() { try { Socket socket = new Socket("192.168.0.107", 19231); // Socket socket = new Socket("127.0.0.1", 19231);//for mocking pw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())); } catch (UnknownHostException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } setLayout(new BorderLayout()); left = new JButton("LEFT"); this.getContentPane().add(left, BorderLayout.WEST); left.addMouseListener(new MouseAdapter() { @Override public void mouseReleased(MouseEvent e) { leftRelease(); // System.out.println("LEFT-RELEASE\n");pw.flush(); } @Override public void mousePressed(MouseEvent e) { leftPress(); // System.out.println("LEFT-PRESS\n");pw.flush(); } }); right = new JButton("RIGHT"); this.getContentPane().add(right, BorderLayout.EAST); right.addMouseListener(new MouseAdapter() { @Override public void mouseReleased(MouseEvent e) { rightRelease(); // System.out.println("RIGHT-RELEASE\n");pw.flush(); } @Override public void mousePressed(MouseEvent e) { rightPress(); // System.out.println("RIGHT-PRESS\n");pw.flush(); } }); up = new JButton("UP"); this.getContentPane().add(up, BorderLayout.NORTH); up.addMouseListener(new MouseAdapter() { @Override public void mouseReleased(MouseEvent e) { upRelease(); // System.out.println("UP-RELEASE\n");pw.flush(); } @Override public void mousePressed(MouseEvent e) { upPress(); // System.out.println("UP-PRESS\n");pw.flush(); } }); down = new JButton("DOWN"); this.getContentPane().add(down, BorderLayout.SOUTH); down.addMouseListener(new MouseAdapter() { @Override public void mouseReleased(MouseEvent e) { downRelease(); // System.out.println("DOWN-RELEASE\n"); } @Override public void mousePressed(MouseEvent e) { downPress(); // System.out.println("DOWN-PRESS\n"); } }); stop = new JButton("STOP\n"); this.getContentPane().add(stop, BorderLayout.CENTER); stop.addMouseListener(new MouseAdapter() { @Override public void mousePressed(MouseEvent e) { sendCommand("STOP"); } }); //keypad arrows work only if the focus is on the stop button //lame but that's life stop.addKeyListener(new KeyListener() { @Override public void keyTyped(KeyEvent event) { // TODO Auto-generated method stub } @Override public void keyReleased(KeyEvent event) { if(KeyEvent.VK_UP == event.getKeyCode()){ upRelease(); } else if(KeyEvent.VK_DOWN == event.getKeyCode()){ downRelease(); } else if(KeyEvent.VK_LEFT == event.getKeyCode()){ leftRelease(); } else if(KeyEvent.VK_RIGHT == event.getKeyCode()){ rightRelease(); } } @Override public void keyPressed(KeyEvent event) { if(KeyEvent.VK_UP == event.getKeyCode()){ upPress(); } else if(KeyEvent.VK_DOWN == event.getKeyCode()){ downPress(); } else if(KeyEvent.VK_LEFT == event.getKeyCode()){ leftPress(); } else if(KeyEvent.VK_RIGHT == event.getKeyCode()){ rightPress(); } } }); pack(); } private void downPress() { sendCommand("DOWN-PRESS"); } private void sendCommand(String command) { try { pw.write(command+"\n");pw.flush(); } catch (IOException e1) { e1.printStackTrace(); } } private void downRelease() { sendCommand("DOWN-RELEASE"); } private void leftPress() { sendCommand("LEFT-PRESS"); } private void upRelease() { sendCommand("UP-RELEASE"); } private void leftRelease() { sendCommand("LEFT-RELEASE"); } private void rightRelease() { sendCommand("RIGHT-RELEASE"); } private void upPress() { sendCommand("UP-PRESS"); } private void rightPress() { sendCommand("RIGHT-PRESS"); } } |
Mock app to test the remote:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
/**
* This was written on jCrete 2015 on a LeJOS session by Steven Chin.
*
* We were given the task to build a lego and do something cool with it.
* We built a pretty large tank and remote-controlled it via wi-fi with
* simple socket commands.
*
* For more info, go to https://mihail.stoynov.com/?p=2909
*
* This is a mock server for testing if you don't have a lego at hand.
*
* @author Nayden Gochev, jug.bg
* @author Mihail Stoynov, jug.bg
*
*/
public class ServerMock {
public static void main(String[] args) throws IOException {
try (ServerSocket server = new ServerSocket(19231);) {
Socket socket = server.accept();
System.out.println("ACCEPTING");
BufferedReader reader = new BufferedReader(
new InputStreamReader(
socket.getInputStream()));
System.out.println(reader.readLine());
String line;
while ((line = reader.readLine()) != null) {
System.out.println("RECIEVED " + line);
}
}
}
}
I've had issues powering an external hdd on a raspberry pi or odroid. I had to buy Y-cable (Y-cable = branched USB cord for dual power).
I found out, that powering the raspberry pi or odroid on the normal USB supplies more power than on the mini/micro-USB they use. The micro/mini USB used for power has a fuse that cannot supply more than 1A, but powering via one of the USB typeA works fine. Of course you would need a Y-cable, because even the most powerful USB chargers cannot produce enough power on one port.
That's another point - most USB chargers say they produce 2A or 2.1A and the crappy ones produce .3A, the good ones go up to .9A. So everybody lies. But .9A is good enough with a Y-cable.
The PI/Odroid use like .5A, the drive uses .3A, but they spike to more than 1Amp.
jCrete is an unconference organized by Heinz Kabutz (author of the Java Specialist newsletter).
*unconference - top people, informal talks, discussions instead of sessions (most in a restaurant or at the beach).
What I learned:
Unsafe is going to be available in jdk9 with a jre switch on startup. Oracle is working on isolating (boundary checks) the unmanaged heap so that
Oracle might introduce a commercial GC with deterministic stop-the-world pauses.
G1 will become the default GC in jdk9.
I will update this accordingly with more info.
A bug report here: https://bugs.openjdk.java.net/browse/JDK-8065424
Information:Using javac 1.8.0_25 to compile java sources Information:java: An exception has occurred in the compiler (1.8.0_25). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you. 'xj-conc-j8' Information:7/14/15, 11:22 - Compilation completed with 1 error and 0 warnings in 2s 319ms Error:java: Compilation failed: internal java compiler error |
Today we had a BGJUG event.
Martin presented RabbitMQ - Spring Framework's default message broker.
I followed the presentation and using Docker's GUI for OSX called Kitematic, easily created a rabbitmq server and a client in a maven project:
Again there was a lot of beer, but since we have been accused of advertising beer brands, there will be no pics.
This sentence commemorates this blog's birthday.
A maven plugin by OWASP that checks if there are CVEs for any of the plugins used in a maven project:
$ mvn org.owasp:dependency-check-maven:check |
A very preliminary view shows there are false positives.
So, jprime.io is over, let's see how well we did:
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Also in my inbox:
Tова което вчера казвах на Найден, че още от първата конференция бяхте много добри.
Поздрави,
—Филип
Translation: Basically Phillip is saying we are the best java conf here.
---
Another one:
Здрасти,Браво за конфа. Получи се доста добре.Готиното беше, че хората наистина се събираха и си говореха.Аз трябваше да тръгна по-рано, че имах малко лични ангажименти,и изпуснах всичко след предпоследната лекция, но това на което бях,наистина беше готино и се усещаше приятелската атмосфера 🙂Браво,Стеф
From: "Stefan Vartolomeev"
Translation: Stef is saying it was nice that people communicated and that the atmosphere was friendly and the feeling altogether was cool.
---
...
I think we did well.
Every morning I wake up to this: and this: . Every day I wage a fruitless war to go down to zero on both fronts and I fail miserably. But I'm getting better.
Recently we managed to "inject" a company as a gold sponsor after all the deadlines have passed. We did it in 20 minutes after 6 phone calls.
The server firewall failed. Someone fixed it on a Saturday morning.
Our invoicing architecture after so many patches fails to follow all the complex branches of the process of issuing an invoice. We somehow manage to still use it fruitfully. And I have big plans for rewriting most of it.
ePay integration was a pain it the ass. Very bad documentation, different undocumented services, support could be better. But it was fun encrypting and decrypting a ton of messages until we stabilized it. We even "support" credit cards (in a way).
Our Turkish speaker delayed his visa application. I called the Bulgarian embassy in Ankara. They were nice, didn't forget to call me back. Actually they kept me updated the whole time. And they issued the visa in less than a day. So kudos to them.
We fight less, work more, plan better, became team players and learned a lot. Organizing a conference is fun.
Go buy a ticket at jprime.io.
I remember when 8 months ago Ivan came up with the idea to organize a conference, we were all - why the hell not. How hard can it be? I want to go back in time and give my cocky past self a slap in the face. A very hard slap.
We had already done many hackatons, pushed a couple of openjdk patches (which are as of now still not accepted) and drank many beers planning the bright future.
I remember feeling a bit in a rut. And this was a really good excuse to write some java code, meet new java people and work with some new java technologies.
I remember when we just talked about the conference for four months. It all got very real 4 months ago and we had a choice - organize the whole thing in 4 months (which then I had no idea was a really short time for a conference) or give up for next year.
We were very eager back then. We all decided to do it. I remember some of our organizers looking at us, probably thinking "let's sit and watch go down in flames".
4 months later I know a lot about accounting and VAT. I wrote a lot of code, most of the times after midnight. The funniest story is when we were deploying the electornic ticket system (epay integration) - proudly written mostly by me (but I'm ashamed of the code).
4 months later I can sign a contract in a couple of hours. A procedure previously taking me almost a week. I have optimized so many of the bureaucracy procedures I do. As a business owner I had the same issues, but after we started the conference I couldn't keep up and had to optimize again and again. Here's the place to send a special thank you for our lawyer and accountant - two of the people I would fail without.
4 months later I sleep less, and I do more. I hope the sleeping part will fix itself after the 27th. I now can read 30 emails in an hour (unfortunately after another hour I have 30 more). Half of my inbox has "Ivan" in the sender's field - he has the nasty habit of putting every little detail in an email, requires the same from me, and is pissed off if I fail to read something 2 hours after he sent it.
One of the funniest stories from the past week is me sitting in an office, signing a contract. The contract has to be signed, and I have to pay that contract in 10 minutes. So I'm sitting on my laptop sending the money, the other side sitting on theirs checking if the money is going to arrive. And at some point it feels as a movie scene where the good guy is going to appear any minute and break the drug deal.
So organizing a conference is tough, but it's a lot of fun. Next time (yes, if I have the opportunity, I'd do it again) it's going to be even better. My conference cherry is about to be popped in 27 days. Hope to see you there.
--Mihail S (and, yes, I know it says "by Admin", but we have more important things to fix first)
Simon Scholz from Vogella presented Eclipse RCP development, the new Eclipse Mars (to be published in a month) and tips and tricks on migrating from eclipse 3 to eclipse 4.
There were also examples on Maven Tycho, SWTBot UI testing. Simon bragged about fixing issues on the dark theme of Eclipse, which I adore, so now it's even better.
Pretty funny, I had to pick Simon from the airport, so I had to have a sign:
window.crypto is a non-standard deprecated firefox API for signing content with a smartcard. My bank uses it, so now I have to either use firefox 32 or use this plugin, that brings back the api infrastructure.
window.crypto is superseded by <keygen>.
March 20th will be the start of the annual SoftUni Conf. I will present Java SE 8' s lambda feature. I expect it to be a fun event.
I use one central email address: stephen@gmail.com (email anonymized). I want to add my work address stephen@fake.company.com to my primary address so I can control it from there.
Gmail cannot use IMAP to download messages (or I haven't found out how) from other mail servers. It can use POP3:
What i prefer is to make the mail server at fake.company.com to forward all the messages to stephen@gmail.com. This depends from server to server.
If you want to pose as stephen@fake.company.com from stephen@gmail.com, you have to use fake.company's email servers, here's how it's done:
On stephen@gmail.com's settings, do:
Gmail -> settings -> accounts -> Add another email address you own
Then add the info of stephen@fake.company.com:
NOTE: Uncheck "Treat as an alias"
Then add the server info:
Then an email with a code will be sent to stephen@fake.company.com
Give the code to gmail:
Now we're ready, compose a new email and put a different FROM address:
Now when you receive an email to stephen@gmail.com designated for stephen@fake.company.com and you click reply, gmail will automatically put stephen@fake.company.com as the FROM address.
NOTE: People on the other side will never know you use stephen@gmail.com.
Today (2015.02.25) we had a bgjug sponsored "intro to nashorn" event.
Mitya, presented nashorn and avatar.js. Gave a lot of examples and had a hands-on - a node.js server working with hibernate.
Today, 17.02.2015, the Bulgarian Java User Group (BGJUG) organized another hackaton. This time we wanted to fix warnings inside the jdk.
First we did
$ make clean JAVAC_WARNINGS="-Xlint:all,deprecation,rawtypes,\ unchecked,cast,serial,dep-ann,static,fallthrough,try,varargs,\ empty,finally -Xmaxwarns 10000" DISABLE_WARNINGS="-Xlint:all"\ LOG=info images |
to generate a build.log
to find out all the warnings. Then with any text editor one could open jdk9/build/linux-x86_64-normal-server-release/build.log
and use these searches (using regular expressions) to find all the warnings:
openjdk/jdk9/corba(.)* warning openjdk/jdk9/jaxp(.)* warning openjdk/jdk9/jaxws(.)* warning openjdk/jdk9/nashorn(.)* warning |
359 corba 100 jaxp 500 jaxws 0 nashorn |
rawtypes 43 unchecked 14 serial 32 cast 10 dep-ann 1 |
Note: Dep-ann is to add the @Deprecated
annotation.
We fixed the last three types and created a patch: http://bgjug.sty.bz/bgjug/~bgjug/fix-warnings-jaxp-part1/webrev.00/, because the unchecked and the rawtypes are a bit tricky as they involve changing public APIs.
We then tried to solve as much of the latter as possible and then created a second patch: http://bgjug.sty.bz/bgjug/~bgjug/fix-warnings-jaxp-full/webrev.00/
barbadan.hit.bg беше сайт с няколко книги за мотоциклетна езда преведени на български. Когато стана ясно, че ще затварят hit.bg и безплатно хостнатнатите там страници, реших да спася цялото творчество и копирах сайта, за да се запази като знание.
Теми:
>Ефективни приоми на уличната езда.
>Кейт Код.
>Снимки.
>Спирачни_накладки_и_дискове_за_мотоциклети.
>ПТП.
>Техника на спортната езда.
Адрес: https://mihail.stoynov.com/barbadan.hit.bg/
Не знам какви са правата на съответните книги/статии. Ако все пак нарушавам нечии, моля да пише.
So we in the Bulgarian Java User Group wanted to build Valhalla, and no IDE (Eclipse, Intellij Idea) supports it. We needed some simple text editor with some java support. And Sublime Text 3 (with Javatar) is the one we chose.
Sublime is a fancy editor written in C and Python. Javatar is a plugin that adds some Java support.
Installing Sublime Text 3 beta is straight forward. Installing Javatar is:
[openjdk@localhost valhalla]$ cd ~/.config/sublime-text-3/Packages/ [openjdk@localhost Packages]$ git clone git://github.com/spywhere/Javatar.git |
Setting up the correct java is: Ctrl+Shift+P --> "javatar" --> Javatar Settings - Default
Then change the javac and java locations:
Creating projects is a bit uneasy - create new project is actually called "Project -> Save as".