frederik witte - Page 3

Preferred data-format for user-data in java applications?

- by Frederik Wordenskjold

I'm currently developing a desktop application in java, which stores user data such as bookmarks for ftp-servers. When deciding how to save these informations, I ended up using xml, simply because I like the way xpath works. I was thinking about json too, which seems more lightweight. What is your preferred way to store data in java desktop applications (in general) and why? What about java-persistence, does that have any advantages worth noting? And how much does the size of user data matter? Its not always possible to store data in a database (or preferable), and in my experience xml does not scale well. Let me know what you think!

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jQuery code not executed

- by Jan-Frederik Carl

Hello, I would like to rephrase my previous question which no one could answer. My problem is that a jQuery-script does not execute a command though it "runs" it. I can see it in the debug mode where the debugger hits the command. Nonetheless, the command is not executed.

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Applying a function to a custom type in F#

- by Frederik Wordenskjold

On my journey to learning F#, I've run into a problem I cant solve. I have defined a custom type: type BinTree = | Node of int * BinTree * BinTree | Empty I have made a function which takes a tree, traverses it, and adds the elements it visits to a list, and returns it: let rec inOrder tree = seq{ match tree with | Node (data, left, right) -> yield! inOrder left yield data; yield! inOrder right | Empty -> () } |> Seq.to_list; Now I want to create a function, similar to this, which takes a tree and a function, traverses it and applies a function to each node, then returns the tree: mapInOrder : ('a -> 'b) -> 'a BinTree -> 'b BinTree This seems easy, and it probably is! But I'm not sure how to return the tree. I've tried this: let rec mapInOrder f tree = match tree with | Node(data, left, right) -> mapInOrder f left Node(f(data), left, right) mapInOrder f right | Empty -> () but this returns a unit. I havent worked with custom types before, so I'm probably missing something there!

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Find images that have a certain HTML class name

- by Frederik Vig

I have some markup that contains certain HTML image tags with the class featured. What I need is to find all those images, add an anchor tag around the image, set the href attribute of the anchor to the images src value (the image path), and lastly replace the images src value with a new value (I call a method that will return this value). <p>Some text here <img src="/my/path/image.png" alt="image description" class="featured" />. Some more text and another image that should not be modified <img src="/my/path/image2.png" alt="image description" /></p> Should become. <p>Some text here <a href="/my/path/image.png"><img src="/new/path/from/method.png" alt="image description" class="featured" /></a>. Some more text and another image that should not be modified <img src="/my/path/image2.png" alt="image description" /></p>

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How do I manipulate a tree of immutable objects?

- by Frederik

I'm building an entire application out of immutable objects so that multi-threading and undo become easier to implement. I'm using the Google Collections Library which provides immutable versions of Map, List, and Set. My application model looks like a tree: Scene is a top-level object that contains a reference to a root Node. Each Node can contain child Nodes and Ports. An object graph might look like this: Scene | +-- Node | +-- Node | +- Port +-- Node | +- Port +- Port If all of these objects are immutable, controlled by a top-level SceneController object: What is the best way to construct this hierarchy? How would I replace an object that is arbitrarily deep in the object tree? Is there a way to support back-links, e.g. a Node having a "parent" attribute?

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HashMap.containsValue - What's the point?

- by Frederik

I've got a HashMap and I need to fetch an item by its integer value. I notice there's a containsValue() function, but it would appear I still have to iterate through the map to find the correct index anyway. My question is; why use containsValue() if I'm required to traverse it afterwards? Also, am I missing the point completely? ;-)

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