It has been 13 years since then and Java went mainstream although applets failed miserably, not really considered for desktop apps and J2EE was too complicated to even build simple stuff but still nothing stopped Java from being the most popular programming language.

It was no surprise, Java is beatiful, type safe and easy to learn language. There were many very good implemantation details in Java such the garbage collector, strings (finalized class), collections which offer great implemantations of merge and quicksort, built in hashcode methods and many more. However, still Java is far from being perfect and may introduce some unexpected behaviour.

The abs bug:
Well this is a very minor flaw but there is a probability that Math.abs() function may return negative value. Weird? actually simple, Java integers can get a value between -2,147,483,648 to 2,147,483,647 which clearly shows -2,147,483,648 can not be represented in positive.
So is this a bug? Well the expected value is positive so yes definitely but in the end this is actually an overflow. So how to fix it? One way would be checking Integer.MIN_VALUE before using abs function or using bit operators to manipulate negative sign instead.

Autoboxing the primitives pitfalls:
Autoboxing makes it easy to work with primitive types and their object counterpart. However moving between them may introduce some unexpected behavior. For example Integer i1=6 can not be compared to Integer i2=6 with == operator where int i3=6 can be compared to those with ==. However using equals may not work as expected too. For example Long x=0L; returns true when x.equals(0L) but returns false when x.equals(0). Weird? Not really since x is long where 0 (without L) is int. So those are not even same object types. Also using primitive types with collections may result unexpected behavior. Finally Autoboxing may result problems in overloading. Lets say we have Integer i=6 and call method sum(i); and we have two sum methods like; sum(long val) and sum(Long val). Which one do you think will be called? Again reasonable but not expected to see at first look and may lead problems in your app.

BigDecimal constructor bug:
If you haven’t already check Java Puzzlers from Joshua Bloch. If you create two Big decimals using double constructor (x1=new BigDecimal(2.00) and x2=new BigDecimal (1.10)) and use subtract (x1.subtract(x2)) you will end up with 0.8999999999. The double constructor of BigDecimal doesn’t work as expected and string constructor needs to be used instead (new BigDecimal(“2.00″)). This might be a serious problem since BigDecimal is widely used for money calculations!

System.out.println pitfall:
println() is one of the first functions that is tought to cs students. It is easy and used often. Usually quite ok to use when you are trying some logic or debugging some values. However System.out is synchronized so acquires a lock when accessed. So using println can cause your app to run in synchronized context which actually means threads will be blocked when accessing println. Imagine a webserver and an app logging with println and you will end up with thread locks and each request waiting for other. So println is ok and useful but not for real apps and logging!

Map bug:
Again take a look at Java Puzzlers from Joshua Bloch, the fifth puzzle(size matters) introduces a strange behavior between an HashMap and an EnumMap where with same values, one map has a size of 2 where the other is 1. Several Map implementations such as IdentityHashMap, EnumMap may introduce this behavior.
Is this a bug? Well certainly we expect same principles from map implementations but Bloch describes that as the spec was not clear at the time.

Cpu Number bug:
This may not be a huge problem unless you really rely on hardware. To get available processor count Java offers Runtime.getRuntime().availableProcessors() method which returns an int number as the number of the processors available. However you may end up getting unexpected numbers if you give a try. For example on my quad-core i7, I get 8. So this method does not return the number of hardware cpus nor the number of cores but the number of execution engines (virtual cores). In my case because quad-core i7s support hyper treading it actually acts like it has eight cores.
So is this a bug? Definitely not since the hardware and the OS acts as if they have that number of physical cpus but still be careful counting if you rely on solid hardware.

Generic arrays
In Java arrays are created as follows, int[] arr=new int[5]; so if you have a generic type of T, you would expect to create a generic array this way: T[]=new T[5]; but simply you can’t. Java does not allow generic array creation and this is actually because generics are implemented in Java using Erasure. Generics are implemented purely in compiler level and actually only one class file is generated for each class. So to create the array we need an ugly cast as follows, T[]=(T[]) new Object[5]; and when you try to compile, the compiler will issue a warning that you are doing an unsafe cast!
Of course this is not bug, it is just an implementation problem given for the sake of simplicity and compability when generics were implemented. But raising a compiler warning on a design issue may confuse someone who faced it for the first time.

So this is definitely not the end of the list but still Java offers a beatiful syntax, type safety and a realiable easy to learn language. And finally no language or implementation is perfect!

Date : March,23 – 13.00

Location: Itu Teknokent . Ari3 Conference Hall

Program: 

• A Mystery Walking in the DART Side, Ali Parmaksız
• Advanced Rich Push Notifications, Erdem Yilmaz
• Node.js PassportJS ExpressJS MiniLab, Salim Kayabaşı
• Neo4J nedir?, Hasan Keklik
• JavaEE6 revisits Design Patterns, Murat Yener

Register at http://gdgistanbul032013-efbnend.eventbrite.com/

www.gdgistanbul.com

The event reached 50% occupancy rate in 2 hours will have great presentations and suprises.

Event Date : 23.02.2013 – 13.00

Event Place : Arı3 Teknokent. İtü

Android ve Elektronik, Muharrem Taç
Guava: Meyve toplamanın incelikleri, Naci Dai
Sihirbaz Programcı, Murat Yener
OpenFrameWorks ve Android, Yağız Hatay
Youtube API, Said Tahsin Dane
Web Crawling, Scraping, Cüneyt Yeşilkaya
NodeJS Herkese Karşı, Salim Kayabaşı

Click here for more information .

MongoDB, Ertuğrul Taş

• MongoDB Giriş, IFUR (CRUD), Neden MongoDB

Merhaba NodeJS, Salim Kayabaşı

• NodeJS Nedir, Neden NodeJS, Google V8, Cloud ve NodeJS

Android, Hasan Keklik

• Rest Api, Maps

mGWT ile Mobil Web, Murat Yener

• HTML5 ve JS yazmadan mobil web!

GWT Application Using Spring Roo to CloudFoundry, Ali Parmaksiz

• GWT MVP, Spring Roo, CloudFoundry

Authentication using New Google Play Services, Said Tahsin Dane

At the end of this course you will understand the best practices in building Internet Applications using JavaEE as well as the core JavaEE Technologies including Servlets, JSP, JNDI, JDBC, and XML. You will understand distributed Web-based JavaEE architectures.

This course teaches students how to build Web Services and Web Service clients using Java technologies. The class includes a high-speed introduction to XML syntax, namespaces, XML Schema, SOAP, and WSDL before exploring Web Service client or server-side development in Java APIs and tools. Specifically, this class focuses on JAX-WS and JAX-RS web service and client development.

Dates:
29 Jan-1 Feb 2013

For more information : http://academy.eteration.com/education/catalog/D-JEE-401-003

For registration:
Zeynep Akgüzel
akademi@eteration.com
+90(212) 328 08 25

Automated testing techniques are covered in detail in this workshop. Indeed, learning how to write more effective tests is an excellent way to write better designed, more maintainable and more reliable code. The course covers fundamental TDD and BDD practices for Java Developers. Continuous Integration, or CI, is a cornerstone of modern software development best practices.

Dates:
18-19 Feb 2013

For more information : http://academy.eteration.com/education/catalog/D-E504

For registration:
Zeynep Akgüzel
akademi@eteration.com
+90(212) 328 08 25

There are various automated test tools used in software test life cycle. In this paper we aim to demonstrate our automated dynamic black box testing approach with Selenium IDE and Webdriver. Selenium is a browser automation framework and Selenium IDE is the integrated development environment that allows recording, editing and debugging tests. It is implemented as a Firefox extension. Once you record a test case using Selenium IDE, the recorded test case can be exported in most programming languages such as Java, .net, Perl, Ruby and HTML.

Webdriver is another automated testing tool for testing web applications. It provides Java API for ease of use and understanding. Simply, it is the process of writing a JUnit or Test NG test case in a Java Project and executing the test case in a “main” method. Any condition in the test case can be controlled using if-else conditions. It provides creating dynamic test cases which means ability of the testing dynamic web pages whose data can be different at any time so that test case can fail.

Blackbox testing is the process of examining functionality of an application without taking into consideration the internal progress. If we think the application is a black box, black box testing approach is about whether the black box gives the same output with the same input. It does not consider what happened in the black box internally. We use Selenium IDE and Webdriver together for automated black box testing.

Let’s assume we will generate a automated test case for booking flight from New York to San Francisco for today. While recording a test case with Selenium IDE, steps are simply:

- Open the web page with a given url.

- Select From

- Select To

- Select today’s date

- Submit

The expected result would be the list of flights. The next step is selecting a flight and making a reservation. With Selenium IDE, we can select a flight and submit the form. But if the selected flight is not available or there is no available flight at all for this date, what will happen? We should control such a case dynamically for execution the test case successfully at any time. In this case, if the flight result list is empty, our test case will fail. Webdriver allows making controls in the test case for any situation.

Why we use Selenium IDE and Webdriver together is because we record a test case using Selenium IDE and edit exported Java code to put any control and execute the test case using Webdriver API. It provides editing exported test case instead of writing all the case from the beginning. There are various cases which exported Java code can’t be executed by Webdriver since some codes are not compatible with Java, but this approach provide generating effective automated test cases for most of the cases.

Business analysis is not only about meeting and writing documents, it has a methodology. This methodology aims to do better work choosing right tools on the right times. Business analysis has a jargon to speak the same language all across the world. This training also highlighted the importance of conflict management and creating a good communication with business, development and test teams.

The main role of a business analyst is to gather requirements from different parties of the project and define Must to Have’s and Nice to Have’s clearly. So, what is a requirement? There are various definitions of the requirement  in BABOK but IIBA classifies requirements like in the following schema:

1. Business Requirements: These requirements define the scope and answer of the question “WHY“.

2. Solution Requirements: This requirements are the answer of the “WHAT” and “HOW“.

- Functional requirement : Functional requirements define “WHAT” the user would do with the system.

- Non- Functional Requirements : These are about usability, performance, security, capacity, speed.

- Business Rules : These are rules of the system defined by business and shows usually parametric informations such as limits etc.

- Assumptions :  It is important to define conditions which are out of the system’s control. Assumptions shouldn’t  be the requirements which are not clear because of conflicts of different parties.

3. System Requirements : These are the answer of “TECHNICALLY HOW” question and usually defined by system analysts.

I strongly recommend all business analysts to read BABOK to do better work with standards in the book. The responsible of the unsuccesfull projects is not the people, it is process followed in the projects.

We will examine three of test tools for mobile testing below.

These tools are GOMO,Ripple and Browser Stack.

GOMO

Gomo is a mobile testing tool that is developed by Google.We can use Gomo when we want to UI testing for websites for mobile devices.We can access Gomo’s interface with http://www.howtogomo.com  on the browser.We doesn’t need to install any programs.Other avantage of Gomo that has a good  and  detailed rapor format.If we want to have report,we get it as pdf format.Also Gomo has simple and useful interface.

We will test a sample website with Gomo below.So that we will examine Gomo in detail.

Let’s examine http://academy.eteration.com with Gomo.

First we open Gomo’s homepage.(Image 1)

Image 1

There are three options in here.The first option is is that why the mobile site is necessary.The second option is for testing websites by mobile devices.And the third option is for make a sample site and its sources.

We choose the second option for testing.Next page is opened.(Image 2)

 Image 2

We click at link in the page.Next page is opened.(Image 3)

Image 3

We enter the websites URL in the textbox and click “TEST YOUR SİTE”.Five options are listed in the page.We choose one of them for our site.When we choose an option, system ask a few questions to us see how your site is working.We answer these questions and click  “GET RESULTS”.Next page is opened.(Image 4)

Image 4

We will see test results in the page as main categories.Also there are a few links in the page.The links are “view full report”,”email full report”,”build your site”,”test another site”.

If  we want to see full report,we click “view full report” link.In this way we get full report as pdf format.

When we click ”email full report” link,the report is sending our email adress.

When we click ”build your site” link,we go to the build site page.(Image5)

Image 5

If we click ”test another site” link,we came back Image 3.

Ripple

Ripple is another mobile testing tool.Ripple is a chrome extension and has specific interface.If  we want to use Ripple for testing,we go to the Chrome web store and add extension to browser.Link is below.

https://chrome.google.com/webstore/search-extensions/ripple

We will test a sample website with Ripple below.So that we will examine Ripple in detail.

Let’s examine http://academy.eteration.com with Ripple.

First we go to the http://academy.eteration.com.

When The site is opened,we click Ripple icon in the browser page. (Image 6)

Image 6

We click “Enable” in the pop up window.Next page is opened. (Image 7)

Image 7

We choose a device options which we want to see our web site.Next page is opened. (Image 8)

Image 8

We can see web site in the virtual device in this page.And a lot of links are listed right and left parts in the page.For example when we want to see horizontal and vertical mode of virtual devices,we select devices option. (Image 9)

Image 9

Also if we want to view website with another platform,we click Platforms link.When we click Information link,selected device informations are displayed.

Browser Stack

Browser Stack is another tool for mobil testing.We can test our sites in a lot of platforms and devices with Browser Stack.Also Browser Stack has functional and useful interface.We can reach Browser Stack with a URL on the browser.We don’t install any programs.Link is below.

http://www.browserstack.com

We will test a sample website with Browser Stack below.So that we will examine Browser Stack in detail.

Let’s examine http://academy.eteration.com with Browser Stack.

First we go to the Browser Stack’s homepage. (Image 10)

Image 10

We see Browser Stack’s interface in here.We can select one of the platform and devices from all of the selections which we want to test our website.And we click “Start Testing” button.When we click button,our website view in the selected virtual device in the page. (Image 11)

Image 11

I think,the different side of this tool from other tools is that has a lot of platforms and devices.So that we can test with a lot of different platforms and devices.

Effective Patterns for JAVA Programming

06-07 Dec 2012 03-04 Jan 2013

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