Tag Archives: Java

Java, Performance

iJUG-Magazin Java aktuell – High Performance Java

Java Aktuell Cover Issue 2/2020
Java aktuell 2/2020

After our presentation at the JUG Saxony Day in 2019, we have been asked to turn the talk into an article for the iJUG-Magazin Java aktuell. The February 2020 issue just got published and features this article. So get yourself the latest Java Aktuell or, if you just want to check out the article, use this link to the PDF and enjoy. The article is in German.

The days where Java was considered a slow bytecode interpreter have ended a long time ago. JVM is using many tricks in order to execute a code efficiently and to transform and optimize a Java code on the used hardware. With some knowledge about these processes, you can avoid working against the JVM system, while achieving more speed. Even if you are not chasing every last microsecond, it is still interesting to see what methods and techniques JVM uses for a better understanding of the runtime environment.

Comments are very welcome.

Interesting Reading, Java, Software Development

Java Training Sessions

Today we are going to publish four of our Java training sessions so you can use the material and benefit from it.

Let’s get started with four direct links to extensive material that might help you to understand Java or code quality better or just help you to reflect on topics you already know.

  • The Java Memory Model: Why you have to know the JMM to understand Java and write stable, correct, and fast code.
  • Java Memory Management: Know more about the size of objects and how Java does garbage collection.
  • High Performance Java: All about the smart Java internals that turn your code into fast code and how you can leverage that knowledge.
  • High Quality Code: The anatomy of high quality code that supports longevity, cross-team usage, and correctness. This is not just about Java, this is about good code in general.

Show a little patience when loading the training, these are all large reveal.js based slide sets. Use the arrow keys or space to navigate. Because the slide sets are designed to be interactive sessions, in many cases, not the entire slide context is revealed at once but block by block.

We publish these training sessions because they are also based on openly shared material, it greatly helped us to advance and understand, as well of course advertise a little what Xceptance might be able to do for you.

We will release more of our material in the next weeks and month, so everybody can browse and learn. This won’t be limited to Java and also cover material about approaching load testing, how to come up with test cases, and more about the modern web and its quality and performance challenges. Of course there will be more Java material too. You can get a glimpse of it when you just follow this link and page through the slides: The Infinite Java Training. Please remember, not all material is complete yet.

If you like the material and you need an audio track aka a real presentation, please talk to us. If you see other training needs in the area of quality assurance, testing, and Java, please contact to us.

More to come.

Automation, Java, Testing

Simplify Your Life With a Little UI Automation

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Are you familiar with someone asking you to do things such as putting all of your clients into the new CRM or inserting 80 new users in a software product x? If so and if your software has no import feature, you probably found yourself copying and pasting all day long. A simple way to save you from this torture is using a UI automation tool like Sikuli Script.

What is Sikuli?

Sikuli automates UI functionalities like mouse, keyboard, and clipboard actions. It works with UI recognition to identify UI components such as buttons, input fields, or menus. To use this kind of recognition, Sikuli compares the actual screen with screenshots from the user.
Continue reading Simplify Your Life With a Little UI Automation →

Automation, Java, Testing, XLT

Handle authentication during WebDriver testing

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Sometimes authentication is necessary before a test case can be executed. While HtmlUnit based tests can easily enter and confirm authentication requests, most browser based tests, cannot workaround the dialog. This is a browser security measure to prevent automated data capture and/or data entering. WebDriver for Firefox delivers a solution for that problem, but IE and Chrome rely on a manual interaction with the browser before the test automation can run.

The following steps describe a solution for the authentication problem and how to run a script test case as WebDriver based test. The key to this solution is the usage of Sikuli, an image based testing tool that directly interacts with the screen to find the right elements by using the screen.
Continue reading Handle authentication during WebDriver testing →

Java, Software Development

Spurious wakeup – the rare event

After hunting for quite some time for a strange application behavior, I finally found the reason.

The Problem

The Java application was behaving strangely in 4 out of 10 runs. It did not process all data available and assumed that the data input already ended. The application features several producer-consumer patterns, where one thread offers preprocessed data to the next one, passing it into a buffer where the next thread reads it from.

The consumer or producer fall into a wait state in case no data is available or the buffer is full. In case of a state change, the active threads notifies all waiting threads about the new data or the fact that all data is consumed.

On 2-core and 8-core machines, the application was running fine but when we moved it to 24-cores, it suddenly started to act in an unpredictable manner.
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Java, Performance, Testing, XLT

XLT – Garbage Collector details visualized

Today we want to give you a small preview of an upcoming XLT feature. Most of you probably know that XLT features agent statistics. These statistics help you to keep an eye on the health of the test execution engines (agents) to ensure that you do not influence the test results by providing insufficient hardware or by applying no or incorrect settings.

Most modern programming languages are virtual machine based and these machines have knobs you can turn to adjust their behavior according to your requirements. XLT runs on Java and so all the things you might have already learnt from tuning your Java-based servers apply to XLT as well. If you do not have experience in tuning your Java-based servers, you will learn a lot that can be applied to your servers and help you to increase performance.
Continue reading XLT – Garbage Collector details visualized →

Java, Performance, XLT

What is the state of the G1 Garbage Collector?

Because I do not know what is the current state of the Java G1 Garbage Collector, I decided to try G1 with JDK6u20. Somehow I was disappointed because after a short moment of predictable GC performance, the entire VM stopped and some major collection was running. You can easily see that in the charts of that run. Right around 20:09:45, the threads were stopped and the entire VM behaved ugly.

The G1 stop the world

So, the G1 is not yet ready for production, of course nobody stated that it is ready for production. If I read the release notes of JDK6u21 correctly, it delivers plenty of G1 changes, so I might try that soon.

Bugs in the Wild, Linux, Software Development, XLT

Eclipse und Ubuntu 9.10

Wer seine eigene Eclipse-Installation unter Ubuntu 9.10 betreibt bzw. ältere Versionen von Eclipse im Einsatz hat, der kennt evenutell Probleme mit Buttons. Diese lassen sich oft mit der Maus nicht klicken oder anwählen. Nur mit Hife der Tastatur kann man noch etwas ausrichten.

Das Ganze ist ein bekanntes Problem seit Ubuntu 9.10 und sollte mit Eclipse 3.5.1 weg sein. Wenn das aber keine Lösung ist, dann muss man seine Umgebung mit diesem Parameter anpassen:

GDK_NATIVE_WINDOWS=true

Danach funktioniert es wieder. Die Lösung habe ich hier gefunden: Widdix – Eclipse unter Ubuntu 9.10 und hier gibt es mehr dazu in Englisch.

Java

Java-GC unter die Haube schauen

Diese Optionen für das JDK6 sollte man kennen, wenn man dem Garbage Collector bei der Arbeit zusehen will. Speziell für das GC-Tuning sind diese Optionen unerlässlich:

Details zu den Optionen und zur Auswertung kann man unter GC Tuning oder in der Liste der JDK-Optionen finden.