406 Not Acceptable

I’ve decided that it would be best to me to hold back any articles on J2Me until after I have finished my project. I am not doing this because I do not have the time, but instead for plagiarism purposes. After all I would be posting code from my project onto this site and that may flag up on some plagiarism detection program and give me some serious hassle. The bigger issue is if anyone steals the content from this site (unlikely) and that gets picked up… then I’d have even more hassle to deal with.

Anyway, expect this stuff in September/October. I’ll have a few articles written ready for when I finish the project.

What’s really annoying is that some people get an extra 4 days to do their coding… that’s not what I’d be calling fair…

J2ME Polish is a really neat package for J2ME programming. Really all I want it for is to change all my annoying Vectors into ArrayLists for speed. Now there are a few issues with the integration plugin on both Windows and Linux when using Netbeans. Heck it doesn’t even work properly on Netbeans 5.5, never mind Netbeans 6, 6.1, or 6.5…

Now what’s the only thing better than a poor integration plugin? No support, that’s what! A quick check on the J2ME Polish forums and you will find numerous posts asking how to fix these errors. So if you’ve tried going to the forums and had no luck (like everyone else,) you’ve come to the right place.

So here are a list of the problems and how to fix them.

 When starting NetBeans it prompts you with a message that states “org.netbeans.modules.java.platform/1 >1.10 required version found 1.9.2″(Or some other version) with options “Disable and continue or Exit”.

This one’s an annoying one, which occurs every now and again. I got this on 6.0 on Linux and 5.5 on Windows, but not with 6.5 on Windows. So how do you fix it?

Go to:

/usr/share/netbeans/platform7/modules

or in Windows (x being a version number)

Program Files\NetBeans 6.x\nb6.x\modules

If you can’t find this folder just search for  “de-enough-polish-netbeans.jar” as this is the file you need to edit. Open up “de-enough-polish-netbeans.jar” with a zip program (Winrar, rileroller, Winzip, etc) and edit the file at META-INF/MANIFEST.MF wih a text editor (notepad.) There will be a sentence that states:

org.netbeans.modules.java.platform/1 > 1.10

Change it to

org.netbeans.modules.java.platform/1 > 1.0

Reactivate the plugin in Netbeans and enjoy!

You are prompted to resolve reference problems relating to “Emulator Platform” or “SUN WTK 2.2 etc…” not being found.

This occurs to everyone…

Go to your an existing (non polish) project folder and open the folder nbproject. There should be a file called project.properties, open this with a text editor. Scroll down and there should be two lines stating:

platform.active=Sun_Java_TM__Wireless_Toolkit_2_5_2_for_CLDC
platform.active.description=Sun Java(TM) Wireless Toolkit 2.5.2 for CLDC

The versions may be different, as you may have a later Wireless Toolkit!

Now open the same file in your J2ME Polish project and replace the platform.active and platform.active.description lines with the ones from the non polish project.

Replace every occurance of “MPowerPlayer” with Sun_Java_TM__Wireless_Toolkit_2_5_2_for_CLDC (or what you had in your old project.)

Replace every occurance of “Emulator Platform” with Sun Java(TM) Wireless Toolkit 2.5.2 for CLDC  (or what you had in your old project.)

Close Netbeans and reopen and all should be fixed!

This picture just had to make it one week:

We got bored waiting for someone to turn up at the pub (and our food,) so we had some fun. The crazy stuff computer science students get up to!

The group project is nearing the deadline and the coding side of the work seems to be complete (bar the guaranteed major bug.) I’ll be pulling another all-nighter tomorrow to help finish off the testing and written work.

After numerous last minute revisions to the protocol and the server everything back working again! Loving it when someone recodes the server, client, or protocol then comes up to you and says: “By the way, your Gui is broke.” Really? It was working when I updated and went to bed >:( Perhaps that has happened too many times in the last 5 days for me to care anymore…

Since I am knacked, heres a lovely (Java ish related) comic from xkcd to keep you entertained:

After installing Netbeans 6 RC 1 I never really turned back to Netbeans 5.5.1, Netbeans 6 enabled me to be far more productive when coding. The highlighting, searching, and better auto commenting features were enough to make me delete Netbeans 5. Especially after the RC was stable enough to work with. Now Netbeans 6.1 beta 2 has recently appeared, it seems I missed out on having a look at beta 1. At least that means I get to test a more stable IDE.

Now the one huge difference with Netbeans 6.1 is the start up speed. It is almost instant, well in Netbeans terms anyway. On my home system — without any tweaks to the IDE — it loads up my last project in just under 10 seconds. Now you probably want to now how long Netbeans 6 takes, well that takes… 17 seconds (yes, I did just count.) So, for me at least, Sun aren’t making things up about the increased speed of the program.

According to Sun:

• Faster cold start and improved startup sequence. Up to 40% faster (with a project opened). Opening projects does not block startup. Go to Type dialog available even during post-startup scanning of sources.
• Various optimizations to reduce I/O and file access (touching disk), improving responsiveness in many situations, especially on slower filesystems (e.g. on network).
• Incremental parsing in java editor speeding up code completion and improving responsiveness of the editor especially with large files (see below).
• Improvements in JSP parser (caching, memory management, update strategies), leading to faster code completion and editor.
• Improvements in Visual Web designer — faster page opening and table drop, lower memory usage, fixed memory leaks, and more (see below).

It seems this major speed improvement is new to beta 2, so if you’re still stuck on beta 1 you might want to change.

There’s also some nice eye candy in there, it seems everyones on the transparency train these days!

I’ve only had one hiccup with the IDE so far, a button just wouldn’t delete in my Gui when using Matisse. I kept getting a little warning light about an error, so I happily submitted the problem. I ended up just tossing the button out of my gui as just one more ‘other component’ (the Netbeans equivalent of tossing it overboard!)

Coding a breadth first traversal is more complex than a depth first traversal (left to right, or right to left.) Although, the code behind the traversal is not much longer or complex, it just requires a bit of thinking. Source code for the breadth first traversal is at the bottom of the post, alongside source code for the more common depth traversal.

I’ve found that there are little examples – online or in books – of how to do a breadth first traversal, especially for Java. I had to teach myself this from a not too friendly C++ example. I’ll try to explain the basic idea of the traversal, before moving on to the code. I hope for your sake that I can actually explain this…

Suppose you have the following tree:

 Now if you were to run a depth traversal you would go in the following order:

1,2,3,4,5,6,7

As the traversal would go to the left most node, then get the root node of that node, then attempt to try this on the right node. As such:

I know, not the greatest of diagrams… that probably just confused you. The red numbers and arrows correspond to the order in which the traversal works. It will go all the way to the left, before going right; this is probably good in the case above, but sometimes you want to get all the values at a certain depth before moving to the next depth (alternatively see this as getting numbers across the breadth of the tree.) For example, if a tutor asked you to get the numbers in order of how close to the root of the tree they were. A normal traversal would not be able to do this, thus you would have to do a breadth first traversal in order to answer the question. Another good example would be searching for a closest ancestor of two people, a basic depth first traversal may get the correct answer on many occasions; however, it would give erroneous answers with more complex trees. If a breadth first traversal was used it would always give the correct answer.

For example, on the tree above a breadth first traversal would give the result:

4,2,6,1,3,5,7

As you can see the numbers are placed in order of their depth, 4 is the root of the whole tree, 2 and 6 are the subnodes of 4. Then finally you get the subnodes of the subnodes (1,3,5, and 7.)

In order to do such a traversal you will need to have two methods and a queue. The first method deals with the root and its subnodes and the second method will deal with all other nodes.

Basically you should dump the subnodes into the queue, then remove one from the queue and repeat the process. The code does a good job in explaining this.

 Now for the code, full source code is available at the bottom of this post.

Basic Traversal

/**
* Simply runs a basic left then right traversal.
*/

public void basicTraversal()
{
//Check if we can go left
if (left != null)
{
left.basicTraversal();
}

//Add the root
list.add(root);

//Check if we can go right
if (right != null)
{
right.basicTraversal();
}
}

Breadth traversal

  /**
* Runs a breadth first traversal
* This method runs once to get the root and it’s subnodes, then runs
* another method to continue the traversal
*
* @param list ArrayList to store the roots in
* @return ArrayList of type Integer
*/
public ArrayList<Integer> getBreadthTraversal(ArrayList<Integer> list)
{

//Add the root to the arraylist, we know it is always the first entry.
list.add(root);

//Basically we add the first set of nodes into the queue for
//traversing.

//Query if left exists
if (left != null)
{
//Then add the node into the tree for traversing later
queue.add(left);
}
//Same for right
if (right != null)
{
queue.add(right);
}

//Then we call the traverse method to do the rest of the work
return traverse(list);
}

/**
* Called by getBreadthTraversal, this should not be ran without it.
*
* This method completes the breadth first traversal. It will remove the
* first Tree from the queue and add their nodes (left and right)
* to the back of the queue. Then it will append the Tree to the
* ArrayList for returning.
*
*
* @param list ArrayList to list tree roots in
* @return list ArrayList
*/
private ArrayList<Integer> traverse(ArrayList<Integer> list)
{
//Keep traversing until we run out of people
while (!queue.isEmpty())
{
/**
* We take one from the queue.
* As a linked list is a queue it operates as “First In First Out”
* also known as FIFO. So if you add something to a queue you have
* to wait until all other objects are removed before you can
* access the object again.
*/
Tree p = queue.remove();

//Check if it has any subnodes
if (p.left != null)
{
//Add the subnode to the back of the queue
queue.add(p.left);
}

//Same for left
if (p.right != null)
{
//Same here, no queue jumping!
queue.add(p.right);
}

//Append to the ArrayList
list.add(p.root);
}

//And return
return list;
}

Tree example source code

With just over one week to go it seems everyone in my Java group is burnt out. This just happens to be the perfect time for such an occurrence…

Work has seriously piled up over the past couple of weeks. I’ve got the main Java project, a bunch of complex SQL queries (because the database is so badly designed,) database diagrams, oh and some UML stuff. All that in just over a week, sounds easy!

In addition, I seem to have taken over the job of creating the GUI for the project – something I did not wish to handle; but with the way everything else is going, I think it would be easier to stick to doing something independent of the main work (the client program the GUI interacts with is pretty much finished.)

Now I am off to try and write some more useful things and do some work