I did a session at 2015.java2days.com about http/2.

Slides:

For more questions, use the comments section.

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.

Videos:

Here's the code:

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);
			}
		}
	}
}

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

• mistakes will not mess up the managed heap
• mistakes will not cause a segmentation fault (crash the whole jvm, because someone is trying to read memory from another process)

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.

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.

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)

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/