Sunday, 30 September 2012

Highlights From Java One: Day 1

Java One - San Francisco

Today was my first day at Java One, and my first international conference. It has been an immensely fun day with loads going on.

8.15 AM - First talk of the conference - ours!

The first session we attended was our talk titled "The bluffers guide to terminology". The talk walked through terminology that complicates our industry, and made observations on how business, technical and academic domains are complicated enough without additional terminology. We walked through the different sections explaining terms and simplifying them so everyone could understand. For 8.15am the audience were very engaged, and it was clear that this was something everyone could relate to. We concluded that you have to be very careful when picking terms to represent your domain model objects in software development. You need to think about having a suitable abstraction that is clear as to what it represents in the domain, but doesn't complicate the domain further.

Winning an award

For the last 18 months, myself and colleagues from the London Java Community have been working on two key initiatives - Adopt a JSR and Adopt Open JDK. Today we were awarded with a Duke's Choice Award for the hard work we have put in inspire the community to be more involved in contributing to the future of Java. It was very exciting to see the LJC's name on the big screens at the Java One keynotes. Although winning an award was not something we set out to achieve, it is an honor. It has inspired me to carry on pushing on the initiatives we started and to use Java One as an opportunity to encourage global participation. It's also got me thinking about a future initiative, but for now that will remain top secret.

Technical Keynote

I'm still processing some of what was in the keynote, but my initial reaction is how excited I am about Java on the desktop. Having experienced the pain of Swing and context switching between .Net and Flex as alternatives, I can really see a future for Java on the desktop. That wasn't all however, we actually got to see Java FX running on a Raspberry Pi and other embedded devices. There's actually an embedded version of the Java One conference scheduler deployed around the hotels! This has really steered my interest for the conference as I'll be looking to attend a large number of Java FX talks this week at Java One. We also have our talk on visualising the Java GC model on Tuesday, which will go into building an application from the beginning in Java FX what we have learnt about the technology and how to use Java FX as a teaching and visualising technology from a slightly different perpective to grids and graphs.


The day ended with collecting the Duke's Choice Award and a party in the street next to the hotel. Most of us have now returned to try and shake the jet lag before a packed day tomorrow.

Wednesday, 12 September 2012

JavaFX Help: Too much animation at the same time!

I am currently working on building a Java memory model teaching tool in JavaFX, the project is available on GitHub. Whilst building the user interface I ran into a performance issue, which is easily worked around using JavaFX. This post gives the detail to the problem and how to easily resolve it.

In the memory model we have several memory sections made of memory blocks. In our application we represent each memory block with a StackPane. This has a Rectangle object at the bottom and a Text object on top of this to represent the current generation that block is in.

A block has three states it can be in:
  • Free - nothing has been allocated here yet.
  • Alive - the block holds some active memory.
  • Dead - the memory in the block has now died and is awaiting garbage collection.

We have potentially several threads that are running against the model allocating and killing memory. The challenge is animating each of the state transitions on the UI. A picture shows the animation in action:

The code segment that we used for the transition is as follows (there might be a better way to do this):

     FadeTransition fadeOldBlockOut = new FadeTransition(Duration.millis(10), view);  
     FadeTransition fadeNewBlockIn = new FadeTransition(Duration.millis(1500), view);  

This code was added to the view object. However, once you get multiple of these firing the application will quickly start to hurt itself to keep up with the transitions required. Having read Java FX Pro 2 I quickly realised that I had taken the wrong approach. Large amounts of updating graphics, especially timeline style animation, does not belong on the main application thread. Thankfully JavaFX has an easy paradigm to resolve the issue.

I created an Object that implements Runnable, which would take the memory block I want to animate in the constructor and perform the logic above:

 class CustomMemoryBlockViewTransition implements Runnable {  
   private final MemoryBlockView view;  
   public CustomMemoryBlockViewTransition(MemoryBlockView view_) {  
     view = view_;  
   public void run() {  

Once you have your Runnable defined (you can also do this as an anonymous inner class) you can simply call the Platform to run the animation at a later point. The Platform keeps a queue of activities submitted and will execute these in order.

 Platform.runLater(new CustomMemoryBlockViewTransition(this));  

Open Crete: Days 2 & 3

Having broken out in to the lobby on day 3 I thought I'd summarise the last few days of the conference and some of the ideas I have been developing based on the conference so far. First an image from down at the sea front, a great spot for thinking - and a surprisingly decent wifi connection :-).

Day 2: Discussion of Mobile Platforms 

Day 2 began with a talk run by Richard Pollock on Objective-C vs Java runtime. The discussion took one of a iOS vs Android platform. One of the main points discussed was the background tasks and the implications of those on both operating systems. I found out about some fairly compelling points from the Android camp around running services that then multiple applications can subscribe to, along with writing code to expect to be terminated at any time. iOS has limited support for background tasks, and you have around 7 options that are event based for a limited range of operations that can potentially run in the background. We got into some specifics surrounding grand central dispatch and how this is a lower level threading than the model presented in Android. All round it was a talk which lead to a great consideration about our own business that we run at StackThread Software

Richard and I took a breakout for the next two sessions to discuss our own business model. This was driven based on the sales of our recent iPhone application Diabetes+. We put the application on sale 2 weeks ago at the price of $3. In 2 weeks we sold 15 copies (with £75 of Google advertising) - a really disappointing amount given the effort that has gone into the application. We made the application free as an experiment for a few days, on the first day we sold 270 copies! Within days we now have 550 copies that users have downloaded and are using for free. This is the equivalent of the units we would usually ship over 2 months of our other paid applications. So what did we get from making this free, nothing except more users to support - one could argue that actually word of mouth might be a good thing. What were really hoping for would be more reviews - which also did not happen. In our breakout we discussed targeting the Android platform, we decided it would be a fun technical challenge - but again would be governed by the apparent race to zero price for applications. We concurred that the best way to distribute applications at the moment seems to be to make it free and have in application purchases. In the end we have decided to pursue a new application that we have had on the back burner which is a Spring MVC project hosted on Amazon Web Services with a JavaScript and HTML 5 front end. Although we will support our current applications in the App Store, there isn't any motivation for us to build further applications unless on commission to do so. The rest of the day was spent unit testing and building out on the prototype we had shelved.

Day 3: Enterprise Git

A situation that is close to my heart within enterprise development is source control. In the last 5 years I have been responsible for migrating systems from CVS to Perforce and rescuing diverged branches of over 6 months (taking a few weeks to resolve). 

The conversation opened with the following considerations, which we would discuss even if not answering completely:
  • Does Git work in an environment with 80 developers, and a few million lines of code?
  • We have no collectively clue about Git in large enterprises.
  • How does having a workflow help with development using Git.
  • Does GitHub impose a desirable work flow?
Marc gave us an overview for those less familiar with git to note how the local repository or "my repository" works for developers. Pointing out the familiar concepts of local check ins and branching. The intro also covered the single point of truth and how this works with GitHub, how SHA takes into account the file meta data as well as the content.

It quickly became apparent that few of us use this in our enterprise jobs, with the exception of Kirk! 

What was new for most of us was rebasing rather than merging, something that I heard of but wasn't sure what the difference was between this and a merge. If the original branch hasn't moved on a merge is effectively the same thing. However, when the main branch has moved on it was almost universally agreed this is a better pattern. 

Git enables better collaboration, especially in teams that are distributed. It also works well for teams that focus on pairing and working together.

We decided that Git is suitable for enterprise for the following reasons:

  • Branching is free and easy. Developing features and merging over large teams is easier than in competitive tools. For teams that run the feature branch model this would significantly improve their development experience.
  • An in house git hub would also help to improve cataloging of systems and applications and encourage employing good standards for sharing code. Although this isn't a source control problem, it might be a step in the right direction for code reuse.
  • Integrate with Jenkins and Gerrit, define a workflow that is suitable for the team and enterprise.
We then put Marc on the spot and pair programmed an example of rebase on the command line. 

Day 3: To OO or not to OO

Interesting debate on whether OO is the right abstraction for modelling today's problems. Conversation went to both extremes of what makes OO good and poor. Discussion was along the lines of where does the business logic best fit and is OO too theoretical to be applicable to modern day business problems. Where does functional programming fit into this?

My personal opinion on the outcome of this was that you need to have a balance on your team between practically biased and theoretically biased individuals. There is no correct answer to what is the best approach to take and it should be aligned with what best fits the businesses current problem. A lot went on in the conversation and I'm sure I'm still developing more ideas on this topic over the next few days.

With most of the delegates heading out for excursions this afternoon, I am looking forward to spending the rest of the day working on our JavaFX talk for tomorrow and the DateTime talk.

Monday, 10 September 2012

Book Review: Pro JavaFX 2

I'm a server side Java developer with 10 years experience, and 2 years experience in Adobe Flex. With Flex taking a recent slating in the press, I decided it was time to broaden my UI experiences to JavaFX and HTML 5 with Java Script. Because I know Java well, and having previous experiences with Swing, I chose JavaFX and this was the book I chose to help me learn the basics.

The first thing to note about this book is it's written by the key people behind the JavaFX technology. The advantage of this is the reader is immediately learning how the platform was designed and intended for use.

The book is split into 10 chapters, each with comprehensive code listings on how the examples and components are built. The chapters are outlined below, along with how I found them useful in the work we have been doing building a basic Java Memory Visualizer in JavaFX.

Getting a Jump Start in JavaFX

The book begins with a brief history of JavaFX, and discusses the original version and the introduction of 2.0. The book goes immediately into an example, building an application using a Java Class extending Application. There's also enough to get started in this chapter with getting Netbeans set up and ready to go to build your applications. There's a lot of content here, so don't let this put you off. There's some important code segments that you will probably need to flick back to along the way. My only observation at this point would be remember that there is still the option of using FXML to simplify a lot of the code that is in this chapter - so this chapter should be viewed as a primer.

Creating a User Interface in JavaFX

We're back out of the deep end now and will be walked through the scene and layouts of creating a typical user interface. This chapter is critical to when you come to build your own UIs. If you want to grab a chapter to help you get started quickly this would be the one. One minor criticism would be this would be a good chapter one, but I can appreciate why leading with an example is good. It really depends on your learning style if you want to read this chapter first. After some theory there is a whole host of examples for you to try and figure out, all with both screenshots and code samples. This is a real codex of information, for me I found reading the first part and trying the second part with my own examples worked best.

Properties and Bindings

Binding is a simple concept, but there are some subtleties that need to be appreciated when building JavaFX applications. The first part of the chapter is split into titles of Understanding X, which makes it easy to refer back to later. Once again, everything is backed up with an appropriate example that demonstrates the power of bindings. This chapter is similar to the previous, the first part of the chapter is easy to read for theory but the latter is example heavy. I'd use the latter part of the chapter as a reference to come back to once you start writing your own code.

Building Dynamic UI Layouts in JavaFX

We used the concepts that are in the Reversi example for the foundations of our Java Memory Visualizer to manipulate memory cells that are on the screen. This example is again in the format of extending Application, but building out components on there. We built our application using FXML based on the information from this chapter. There is enough in this chapter to build your own board game, or if you are building any binding state UI I'd recommend reading this chapter.

Using the JavaFX UI Controls

I personally haven't read this chapter in great depth as I view it as a reference chapter. It looks like this is the codex for building your own controls.

Collections and Concurrency

In chapter 6 we're really going back to basics, so in my opinion this is not a chapter you can shelve for later. For the collections part, if you are familiar with Flex, ObservableList reminded me of ArrayCollection. The concurrency section introduces the threading model that is used in JavaFX, and that it is single threaded like most other UI frameworks. The JavaFX tasks are then explained for removing logic from the main application thread to avoid bloating your application re-render. Personally when we approached this, due to the nature of the simulation, we used plain old java.util.concurrent.

Creating Charts in JavaFX

Great overview into building charts in JavaFX and shows off the power of what is capable in the API. Examples and screenshots are available to get you started with what you are trying to build.

Using the Media Classes

Because of the type of work I do it's likely I'll never get to do any of the fun stuff in this chapter. I've saved this one for a rainy day, although on a quick parse it does look like a chapter I will genuinely come back to.

Accessing Web Services

An awesome chapter with practical examples of how you would integrate your JavaFX client with real world technologies. This sample walks you through creating a REST API call to twitter, using JAXB to create an appropriate response and display the information. If you are looking at using this for EE work this would be a good chapter to read. 

JavaFX Languages Markup

In this chapter we see some other languages using JavaFX (Scala and Groovy). The finally we get to the section on FXML. The sample is fairly simple and somewhat limited, it would have been good to have seen more of this earlier. 


This is an excellent book to have if you are trying to do anything with JavaFX. Although the online documentation is getting better, this book provides an awesome introduction to most components, tricks and tips that you would need to get started in this space. My only criticism of the book is a lack of FXML examples and that it only really appears at the end of the book. This shouldn't take away however from some of the excellent explanations and examples in this unfamiliar space. It's also worth noting that with a bit of playing around it's very simple to convert the samples over to using FXML. 

5/5 - I bought this with my own money and don't want it back :-). 

Open Crete: Day 1

A picture says a 1000 words!

Arriving on Saturday was definitely a great idea, as most of Sunday was spent sleeping or taking in these fantastic surroundings. The conference kicked off last night with a informal get to know each other at a local restaurant called Irene's Taverna.

Open Crete is run as an unconference, that is the participants very much direct the success and the output of the conference in the end. No sessions are planned up front, and the first part of this morning was grabbing some sticky notes and proposing sessions. I have proposed 3 sessions (which are pretty much inline with my talks coming up at JavaOne):

  • Why is the community important to Java? Adopt-a-JSR, OpenJDK and JUGs.
  • JavaFX Memory Visualisation.
  • An overview of the new DateTime API (JSR-310) in Java 8. 

We kicked off with two sessions this morning, which covered the future of Java. The general feeling was that modules is going to be a massive section missing from the next release of Java. It was acknowledged however that most of us have not seen the proposed profiles solution. After modules we discussed the impact of Lambdas. Although people are in general excited about Lambdas and what they can do, there is a concern that they will be perhaps used for the sake of using them and in some cases ignored because they are not understood. After discussing some consumer trends, we chatted about the future of Java given that there is currently no substantial mobile presence. The big feel is that laptops will soon become a "developer only" style tool - because regular consumers can get away with carrying an iPad. What does this mean for Java's future? Who is really behind driving Java forwards? 

The session definitely left food for thought as we break for afternoon of activities, and I am looking forward to considering the above in more detail as the week unfolds.

JavaFX Cleanly Closing an FXML Based Application

Whilst developing an FXML based JavaFX application for JavaOne I had to overcome the problem of cleaning up Java background threads running in the controller on a ExecutorService.

If you had chosen to use the builder patterns rather than FXML this is a fairly trivial task, as you are likely to have direct access to the controller from your main class which extends Application. However, when you use FXML you will more than likely be declaring your controller as follows:
 <VBox xmlns:fx="" fx:controller="com.jclarity.anim.memory.MemoryController"> ...  

When you launch the FXML you are likely to do something along the lines of:

 public void start(Stage stage) throws Exception {  
    Parent root = FXMLLoader.load(getClass().getResource("MemoryMainView.fxml"));  
    Scene scene = new Scene(root, 600, 500);  
    stage.setTitle("JavaFX Memory Visualizer");;  

At this stage you launch the FXML and never grabbed hold of your reference to the controller. This now means when you override stop() you can't delegate this to your controller. The solution I found to this was to separate out the code above to ensure that you keep access to the FXML loader. If you have access to the FXMLoader you easily do the following in the stop method:
   public void stop() {  
     ((MemoryController) fxmlLoader.getController()).haltSimulation();  

I separated the code as follows:
 private FXMLLoader fxmlLoader;  

   public void start(Stage stage) throws Exception {  
     URL location = getClass().getResource("MemoryMainView.fxml");  
     fxmlLoader = new FXMLLoader();  
     fxmlLoader.setBuilderFactory(new JavaFXBuilderFactory());  
     Parent root = (Parent) fxmlLoader.load(location.openStream()); 

Friday, 7 September 2012

Book Review: The Well Grounded Java Developer

I have been a Java developer for over 10 years, with 5 years of this in the financial software industry. In my opinion this book is one of the best Java books on the market currently. There is something in this book for everyone, if you are new graduate it helps to consolidate your skills in Java. If you're an old hat, this book has a refreshing approach to more complex topics, such as Understanding Performance Tuning which Dr Heinz Kabutz brands as: "The first book since Jack Shirazi’s Java Performance Tuning that has captured the essence of how to make your system faster." in the foreword. I think the two chapters understanding performance tuning and modern concurrency are a must read for all developers, and are delivered superbly for all levels.

The book is split into 4 parts, starting with an introduction to Java 7. Anyone who has been asleep for the last year should definitely be reading this section. It presents all the major changes with examples, and is easy to follow and read. 

Vital techniques then takes a deep dive into dependency injection - critical to writing testable and maintainable code. The section shows by example an introduction to the critical topic. It also introduces JSR-330 annotations, which as an early adopter of Spring I hadn't looked at in detail myself. The spin then goes into concurrency, and this chapter I finished! Having had Modern Concurrency in Practice on the bookshelf, 4 attempts at reading it and bottoming out around page 50 - I have to say this was refreshing. Modern Concurrency is a great book, but this chapter synthesises the complexity in simple and easy to understand diagrams and explanations. Class files and byte code is another section that many Java developers lack a detailed understanding of - this book adequately covers this topic. It also introduce the opcode detail of invoke dynamic and how that will be useful for developers. The final chapter in this section dives in to understanding performance tuning, which takes a very pragmatic and evidence based approach to finding out why your application might be running "badly". I like this section a lot because it's written from experience, some of the same problems I have run into in my career could have been avoided by reading this chapter first. It also goes into detail about garbage collection basics and structures, a topic which is usually a guaranteed interview question. Also if you thought that Objects were always allocated on the heap, check out page 181 for something you might have missed :-).

At this point your brain might be fried, if so another read of it will make everything clearer. There's hints and tips in the sections for stuff you can skip and that's really useful for the first parse. The next section is slightly easier going and introduces polygot programming on the JVM. If you haven't come across many functional languages this starts with introducing the key concepts and how the compare with traditional Java approaches. We then get the detail of how this all works and we're ready to go with trying out our first functional languages. We get a overview introduction to Groovy, Scala and Clojure. I didn't read these chapters in too much detail purely because of the work I'm doing at the moment. However, I did like the presentation format of is this right for my project, some of the higher level concepts (with solid examples) as well as interoperability with Java. To me this is going to be my holiday reading to see what is going on outside the core space, providing a primer that will be enough for me to go off and do my own research and experimentation.

The final part is about craft, craft is perhaps the one thing that is missing from day to day developers I come across. Craft makes you stand out, it makes you professional and caring about the product that you will deliver. This is one skill you can't get a qualification for, it grows from experience, learning from other and striving to deliver the best you can. The section introduces some key points and approaches you can apply starting today. The chapter on test driven development is another hidden gem in this book, having worked at establishment where testing is finding the problem in production this introduction brought about a new approach to the way me (and my team) now go about writing code. This approach gives you the building blocks of learning these valuable techniques and gives you some hints and tips into different tools you can use to support you with this. Writing good code is all well and good, but how do you ensure it works well with other people's changes and passes coding standards? The continuous integration chapter details how this works using Jenkins as the example. Of course no section of building would be complete without a mention of Maven, I'll let you decide if that's a good or a bad thing :-)!

The book wraps up with web development and looks at why Java is not necessarily the best tool in the box for this, followed by how to stay well grounded now you have been armed with a book!

I have bought and read many technical books in the past and there are only two technical books I've ever read cover to cover, Spring in Action was one of them this is the other. The book focuses on Java 7, which although out for a year is slowly creeping into production systems. The book serves as a good primer to the new changes. 

I wouldn't consider this a very beginner book, if you are looking to learn object oriented programming from the beginning I'd recommend reading another book first. It's not criticism of the book, but if that's what you're looking for I'd consider this book as the second book you buy.