Visualization of Java Concurrent Package

There is a good job here. It can help us to understand topics easily.

download


Download the jar file and run it via: java -jar /home/serkans/Downloads/concurrentanimated.jar

Get Desktop Snapshot with Java

import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.io.File;

public class Screenshooter {
  public static void main (String[] args) throws Exception {
    Screenshooter screenshooter = new Screenshooter ();
    screenshooter.captureScreen ("/tmp/desktopSnapshot.png");
  }

  public void captureScreen (String fileName) throws Exception {

    Dimension screenSize = Toolkit.getDefaultToolkit ().getScreenSize ();
    Rectangle screenRectangle = new Rectangle (screenSize);
    Robot robot = new Robot ();
    BufferedImage image = robot.createScreenCapture (screenRectangle);
    ImageIO.write (image, "png", new File (fileName));

  }

}

Get stack trace and follow your execution path

Sometimes you don't have enough time to analyse source application architecture/UML diagrams etc.
If it is an urgent issue (needed to be FIX asap like always :-p) you want to learn program execution path to understand what it is doing !

new Throwable ().printStackTrace(); gives you what you want

Lets have a look at it.

public class GetStackTrace {
  public static void main (String[] args) {
    GetStackTrace obj = new GetStackTrace ();
    obj.methodOne();
  }
  public void methodOne (){
    System.out.println (" -- im in the method one.");
    methodSeven ();
  }
  public void methodTwo (){
    System.out.println (" -- im in the method two.");
    methodFour();
  }
  public void methodThree (){
    System.out.println (" -- im in the method three.");
  }
  public void methodFour (){
    System.out.println (" -- im in the method four.");
    methodSix ();
  }
  public void methodFive (){
    System.out.println (" -- im in the method five.");
  }
  public void methodSix (){
    System.out.println (" -- im in the method six.");
    new Throwable ().printStackTrace();
    methodFive ();
  }
  public void methodSeven (){
    System.out.println (" -- im in the method seven.");
    methodTwo ();
  }
}

And it's output is here :


-- im in the method one.
-- im in the method seven.
-- im in the method two.
-- im in the method four.
-- im in the method six.
java.lang.Throwable
at GetStackTrace.methodSix(GetStackTrace.java:26)
at GetStackTrace.methodFour(GetStackTrace.java:19)
at GetStackTrace.methodTwo(GetStackTrace.java:12)
at GetStackTrace.methodSeven(GetStackTrace.java:31)
at GetStackTrace.methodOne(GetStackTrace.java:8)
at GetStackTrace.main(GetStackTrace.java:4)
-- im in the method five.

Custom Event Handler in Java

An Event Class which will be produced by producers and listened by listeners.

public class CustomEvent implements java.io.Serializable{
  
  private int eventType = 0;
  private String eventDetail = "";
  
  public String getEventDetail () {
    return eventDetail;
  }

  public int getEventType () {
    return eventType;
  }

  public void setEventDetail (String eventDetail) {
    this.eventDetail = eventDetail;
  }

  public void setEventType (int eventType) {
    this.eventType = eventType;
  }
}

An Interface which is a contract between event producers and listeners.

public interface EventListenerIntf {
  public void handleEvent (CustomEvent event) throws Exception;
}

An Event Listener

public class EventListener implements EventListenerIntf{
  public EventListener () {
    EventProducer.addListener (this);
  }

  private String name  = null;
  
  public void handleEvent (CustomEvent event)  {
    System.out.println ("Event handled by "+ this.name+" : EventType: "+event.getEventType()+" EventDetail :"+event.getEventDetail());
  }

  public String getName () {
    return name;
  }

  public void setName (String name) {
    this.name = name;
  }

}

A Producer which produces events and have its listener list.

public class EventProducer {
  private static List listenerList = new java.util.ArrayList ();

  public static synchronized void addListener (EventListener listener) {
    listenerList.add (listener);
  }

  public static synchronized void produceEvents () {
    CustomEvent event1 = new CustomEvent ();
    event1.setEventType (1);
    event1.setEventDetail ("event1 detail");
    notifyEventListeners (event1);
    
    CustomEvent event2 = new CustomEvent ();
    event2.setEventType (2);
    event2.setEventDetail ("event2 detail");
    notifyEventListeners (event2);
    
    CustomEvent event3 = new CustomEvent ();
    event3.setEventType (3);
    event3.setEventDetail ("event3 detail");
    notifyEventListeners (event3);
    
    CustomEvent event4 = new CustomEvent ();
    event4.setEventType (4);
    event4.setEventDetail ("event4 detail");
    notifyEventListeners (event4);
  }

  public static void notifyEventListeners (CustomEvent event) {
    for (EventListener listener : listenerList) {
      listener.handleEvent (event);
    }
  }
}

Lets make a simple test these with a simple scenario.

public class Test {
  public static void main (String[] args) {
    //Listeners getting up !
    EventListener amy = new EventListener ();
    amy.setName ("Amy");
    EventListener april = new EventListener ();
    april.setName ("April");
    EventListener eli = new EventListener ();
    eli.setName ("Eli");

    // Producer will create some events
    EventProducer.produceEvents();
    
    System.out.println (" good bye");
    System.exit (0);
  }
}

And out output is :

Event handled by Amy : EventType: 1 EventDetail :event1 detail
Event handled by April : EventType: 1 EventDetail :event1 detail
Event handled by Eli : EventType: 1 EventDetail :event1 detail
Event handled by Amy : EventType: 2 EventDetail :event2 detail
Event handled by April : EventType: 2 EventDetail :event2 detail
Event handled by Eli : EventType: 2 EventDetail :event2 detail
Event handled by Amy : EventType: 3 EventDetail :event3 detail
Event handled by April : EventType: 3 EventDetail :event3 detail
Event handled by Eli : EventType: 3 EventDetail :event3 detail
Event handled by Amy : EventType: 4 EventDetail :event4 detail
Event handled by April : EventType: 4 EventDetail :event4 detail
Event handled by Eli : EventType: 4 EventDetail :event4 detail
good bye

Java WebService Example : JAXWS

A Class which is a web service

package jaxws;
import javax.jws.WebMethod;
import javax.jws.WebService;

@WebService
public class Hello {
    private String message = "Hello, ";

    public void Hello() {}

    @WebMethod
    public String sayHello(String name) {
        return message + name + ".";
    }
}

A Class which exposes this web service

package jaxws;
import javax.xml.ws.Endpoint;

public class Server {

    protected Server () throws Exception {
        System.out.println ("Starting Server");
        Object implementor = new Hello ();
        String address = "http://localhost:9000/SoapContext/SoapPort";
        Endpoint.publish (address, implementor);
    }

    public static void main (String args[]) throws Exception {
        new Server ();
        System.out.println ("Server ready...");
        System.out.println (" -- Press any key to exit...");
        System.in.read ();
        System.out.println ("Server exiting");
        System.exit (0);
    }
}

Get the WSDL from Server : Open the url with your internet browser : http://localhost:9000/SoapContext/SoapPort?wsdl

Create a project for this wsdl via SOAPUI and send requests.So simple!

Sample DateTimeFormatter with locale

Do not change locale system wide , do not disturb others!
Create different locales and formatters with given locale and use them.

import java.text.*;
import java.util.*;

public class DateTimeFormatter {

    private static final Locale ukrainianLocale = new Locale ("uk", "UA");
    private static final Locale russianLocale = new Locale ("ru", "RU");
    private static final Locale englishLocale = new Locale ("en", "EN");

    public static DateFormat ukranianDateFormatter;
    public static DateFormat russianDateFormatter;
    public static DateFormat englishDateFormatter;

    public DateTimeFormatter (String dateFormatPattern) {
        ukranianDateFormatter = new SimpleDateFormat (dateFormatPattern, ukrainianLocale);
        russianDateFormatter = new SimpleDateFormat (dateFormatPattern, russianLocale);
        englishDateFormatter = new SimpleDateFormat (dateFormatPattern, englishLocale);
    }

    public static String format (Date date, String lang) {
        String formattedDateTime;
        if ("ru".equalsIgnoreCase (lang)) {
            formattedDateTime = russianDateFormatter.format (date);
        } else if ("en".equalsIgnoreCase (lang)) {
            formattedDateTime = englishDateFormatter.format (date);
        } else {
            formattedDateTime = ukranianDateFormatter.format (date);
        }
        return formattedDateTime;
    }

    public static void main (String[] args) {
        DateTimeFormatter df = new DateTimeFormatter ("dd/MMM/yy HH:mm");
        Date now = new Date ();
        System.out.println ("uk date:" + df.format (now, "uk"));
        System.out.println ("en date:" + df.format (now, "EN"));
        System.out.println ("ru date:" + df.format (now, "ru"));
    }
}

uk date:03/трав/10 16:17
en date:03/May/10 16:17
ru date:03/май/10 16:17