On my trip to Berlin for the Scala Days conference, I used Passbook for the first time to store my boarding pass. I thought it would be interesting to share this first paperless boarding experience with you. When I did the check-in on Swiss’ website the day before my flight…

I have stumbled upon a weirdness regarding the behavior of readLine in Scala (at least with my current basic understanding of the language). The following snippet is supposed to read three times a line from standard in. But it reads 3 times the same line (the first). [code] (1 to 3) foreach { val line = Console.readLine i => println(line) } [/code] while the following snippet (very similar) behaves as expected (reading the three first line from stdin):

Java quiz of the day (easy): what gives Object[] a = new Integer[]{}; List<Object> b = new ArrayList<Integer>(); Response: we get an exception on the second line: Type mismatch: cannot convert from ArrayList<Integer> to List<Object> Arrays and Generics are not consistent. While for arrays, an array of some type is…

What gives: Integer a = 100, b = 100; Integer c = 200, d = 200; System.out.println( (a == b) == (c == d) ); // A Response: counter intuitively, the program prints ‘false’ out. Integer in Java is a non-native class, where ‘==’ means ‘reference equality’ (two variables are reference equal if they are pointing to the same object). From there we would expect the expression of line (A) to be reduced to ‘false == false’, but it is slightly more complicated: the Integer class has the particularity that all Integer (like Short) in the range [-128, 127] are shared. This means the two variables ‘a’ and ‘b’ are actually pointing to the same shared object. Hence the expression of line (A) is in fact reduced to ‘true == false’.

What gives Double a = null; Double b = a == null ? a : 1.0; Response: as strange as it can seem at first look, b is not equal to null after the second statement, but the code produces a NullPointerException. The reason for that is the type of the second expression (double) inside the ternery operator. The first expression ‘a’ of type Double is unboxed to double (calling doubleValue() on ‘a’ which is null), causing the NPE.

I was just checking which commands are supporting sparse files. I post hereafter a short overview of what I found out (working on Linux). Create a sparse file of 20 GiB: dd if=/dev/zero of=foo bs=1 count=1 seek=20G Check that a file is sparse: ls -alsh Compare the first versus second size column (the first one is the space taken on disk). Copy a sparse file: cp foo bar Copy already detects and handles correctly sparse files.

A sparse file is a file which does not take more space on disk than needed. Such a file is usually used to store a partition image on disk, for instance with a virtualization solution like Xen. It’s super easy, to know if a file is sparse or not. …

I had posted that some times ago on Twitter. There is a new version of the excellent GPGMail plug-in for Mail (OS X). Grab it, if you haven’t already. GPGMail for OS X 10.6.2 Just put it inside ~/Library/Mail/Bundles and restart Mail. (More information on GPGMail’s web page.) Edit: This is not an official version of GPGMail. There is still no official version of GPGMail compatible with Snow Leopard.

Check out my new mix 03. Extrabright Mix 03: electro to house with a squeeze of detroit and a drop of chill-out. Among others Gui Borrato, SMD remixed by DJ Pierre, Jori Hulkkonen, Miss Kittin & The Hacker, Mosca, Josh Wink, Black Dog, Clark plus a bunch of other great stuffs. [audio:Extrabright_Mix_03.mp3]