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• Method hiding with interfaces

  - by fearofawhackplanet

  interface IFoo { int MyReadOnlyVar { get; } } class Foo : IFoo { int MyReadOnlyVar { get; set; } } public IFoo GetFoo() { return new Foo { MyReadOnlyVar = 1 }; } Is the above an acceptable way of implementing a readonly/immutable object? The immutability of IFoo can be broken with a temporary cast to Foo. In general (non-critical) cases, is hiding functionality through interfaces a common pattern? Or is it considered lazy coding? Or even an anti-pattern?

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• javac - differences between classpath and sourcepath options

  - by Alex

  Hi, I read the Sun documentation and a lot of Q/A on SO but I'm still a little bit confuse regarding the differences between the javac options -cp and -sourcepath. Let say I have this directory structure: c:\Java\project1\src (where the .java source files are) c:\Java\project1\bin (where the .class will be or are already) The class source MainClass.java is in a package "com.mypackage" and the directory structure is ok in src. I'm in the project1 directory. I run c:\Java\Project1\javac -d bin -sourcepath src src/com/mypackage/MainClass.java or c:\Java\Project1\javac -d bin -classpath src src/com/mypackage/MainClass.java and I obtain the same result. In verbose mode, the search path for source files is src in both cases. If anybody could help me figure out the specifics of these options, it would be great. Thank you.

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• Best Way to Generate Unique and consecutives numbers in Oracle

  - by RRUZ

  I need to generate unique and consecutive numbers (for use on an invoice), in a fast and reliable way. currently use a Oracle sequence, but in some cases generated numbers are not consecutive because of exceptions that may occur. I thought a couple of solutions to manage this problem, but neither of they convincing me. What solution do you recommend? Use a select max () SELECT MAX (NVL (doc_num, 0)) +1 FROM invoices Use a table to store the last number generated for the invoice. UPDATE docs_numbers SET last_invoice = last_invoice + 1 Another Solution?

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• Java's ThreadPoolExecutor equivalent for C#?

  - by chillitom

  Hi Guys, I used to make good use of Java's ThreadPoolExecutor class and have yet to find a good equivalent in C#. I know of ThreadPool.QueueUserWorkItem which is useful in many cases but no good if you want to control the number of threads assigned to a task or have multiple individual queues for different task types. For example I liked to use a ThreadPoolExecutor with a single thread to guarantee sequential execution of asynchronous calls.. Is there an easy way to do this in C#? Is there a non-static thread pool implementation? Thanks, T.

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• Grails/Spring HttpServletRequest synchronization

  - by Jeff Storey

  I was writing a simple Grails app and I have a spot in a gsp where one of my java beans in modified. <g:each in="${myList}" status="i" var="myVar"> // if the user performs some view action, update one of the myVar elements </g:each> This works, but I don't think it's quite threadsafe. myList is an http request variable but in cases of pages that use ajax (or other client side manipulations), it is possible for two threads to be modifying the same request scope variable The Spring AbstractController class provides a setSynchronizeOnSession method. Does grails provide any equivalent functionality? If not, what's the best way to protect this non-threadsafe mutation? thanks, Jeff

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• How to get parent node in Stanford's JavaNLP?

  - by roddik

  Hello. Suppose I have such chunk of a sentence: (NP (NP (DT A) (JJ single) (NN page)) (PP (IN in) (NP (DT a) (NN wiki) (NN website)))) At a certain moment of time I have a reference to (JJ single) and I want to get the NP node binding A single page. If I get it right, that NP is the parent of the node, A and page are its siblings and it has no children (?). When I try to use the .parent() method of a tree, I always get null. The API says that's because the implementation doesn't know how to determine the parent node. Another method of interest is .ancestor(int height, Tree root), but I don't know how to get the root of the node. In both cases, since the parser knows how to indent and group trees, it must know the "parent" tree, right? How can I get it? Thanks

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• How do I use master page container in partial view

  - by user200295

  I have several partial views with Javascript that I am trying to move to the bottom of the page. To do this I am trying to use a container in the master page Master Page - <asp:ContentPlaceHolder ID="Foot" runat="server"></asp:ContentPlaceHolder> Partial view(ascx) <asp:Content ID="header" ContentPlaceHolderID="head" runat="server"> ... </asp:Content> But I get this error Parser Error Message: Content controls have to be top-level controls in a content page or a nested master page that references a master page. So how do I ensure that the Javascript for the partial view is at the bottom of the page? Especially in cases where the html layout needs to be at the top of the page?

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• SQL - Two foreign keys that have a dependency between them

  - by Brian

  The current structure is as follows: Table RowType: RowTypeID Table RowSubType: RowSubTypeID FK_RowTypeID Table ColumnDef: FK_RowTypeID FK_RowSubTypeID (nullable) In short, I'm mapping column definitions to rows. In some cases, those rows have subtype(s), which will have column definitions specific to them. Alternatively, I could hang those column definitions that are specific to subtypes off their own table, or I could combine the data in RowType and RowSubType into one table and work with a single ID, but I'm not sure either is a better solution (if anything, I'd lean towards the latter, as we mostly end up pulling ColumnDefs for a given RowType/RowSubType). Is the current design SQL Blasphemy? If I keep the current structuree, how do I maintain that if RowSubTypeID is specified in ColumnDef, that it must correspond to the RowType specified by RowTypeID? Should I try to enforce this with a trigger or am I missing a simple redesign that would solve the problem?

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• Postgres pg_dump dumps database in a different order every time

  - by behrk2

  Hello, I am writing a PHP script (which also uses linux bash commands) which will run through test cases by doing the following: I am using a PostgreSQL database (8.4.2)... 1.) Create a DB 2.) Modify the DB 3.) Store a database dump of the DB (pg_dump) 4.) Do regression testing by doing steps 1.) and 2.), and then take another database dump and compare it (diff) with the original database dump from step number 3.) However, I am finding that pg_dump will not always dump the database in the same way. It will dump things in a different order every time. Therefore, when I do a diff on the two database dumps, the comparison will result in the two files being different, when they are actually the same, just in a different order. Is there a different way I can go about doing the pg_dump? Thanks!

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• What is wrong with the JavaScript event handling in this example? (Using click() and hover() jQuery

  - by Bungle

  I'm working on a sort of proof-of-concept for a project that approximates Firebug's inspector tool. For more details, please see this related question. Here is the example page. I've only tested it in Firefox: http://troy.onespot.com/static/highlight.html The idea is that, when you're mousing over any element that can contain text, it should "highlight" with a light gray background to indicate the boundaries of that element. When you then click on the element, it should alert() a CSS selector that matches it. This is somewhat working in the example linked above. However, there's one fundamental problem. When mousing over from the top of the page to the bottom, it will pick up the paragraphs, <h1> element, etc. But, it doesn't get the <div>s that encompass those paragraphs. However, for example, if you "sneak up" on the <div> that contains the two paragraphs "The area was settled..." and "Austin was selected..." from the left - tracing down the left edge of the page and entering the <div> just between the two paragraphs (see this screenshot) - then it is picked up. I assume this has something to do with the fact that I haven't attached an event handler to the <body> element (where you're entering the <div> from if you enter from the left), but I have attached handlers to the <p>s (where you're entering from if you come from the top or bottom). There are also other issues with mousing in and out elements - background colors that "stick" and the like - that I think are also related. As indicated in the related question posted above, I suspect there is something about event bubbling that I don't understand that is causing unexpected behavior. Can anyone spot what's wrong with my code? Thanks in advance for any help!

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• Condition checking vs. Exception handling

  - by Aidas Bendoraitis

  When is exception handling more preferable than condition checking? There are many situations where I can choose using one or the other. For example, this is a summing function which uses a custom exception: # module mylibrary class WrongSummand(Exception): pass def sum_(a, b): """ returns the sum of two summands of the same type """ if type(a) != type(b): raise WrongSummand("given arguments are not of the same type") return a + b # module application using mylibrary from mylibrary import sum_, WrongSummand try: print sum_("A", 5) except WrongSummand: print "wrong arguments" And this is the same function, which avoids using exceptions # module mylibrary def sum_(a, b): """ returns the sum of two summands if they are both of the same type """ if type(a) == type(b): return a + b # module application using mylibrary from mylibrary import sum_ c = sum_("A", 5) if c is not None: print c else: print "wrong arguments" I think that using conditions is always more readable and manageable. Or am I wrong? What are the proper cases for defining APIs which raise exceptions and why?

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• Is a class that is hard to unit test badly designed?

  - by Extrakun

  I am now doing unit testing on an application which was written over the year, before I started to do unit-testing diligently. I realized that the classes I wrote are hard to unit test, for the following reasons: Relies on loading data from database. Which means I have to setup a row in the table just to run the unit test (and I am not testing database capabilities). Requires a lot of other external classes just to get the class I am testing to its initial state. On the whole, there don't seem to be anything wrong with the design except that it is too tightly coupled (which by itself is a bad thing). I figure that if I have written automated test cases with each of the class, hence ensuring that I don't heap extra dependencies or coupling for the class to work, the class might be better designed. Does this reason holds water? What are your experiences?

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• MySQL - are FK's useful / viable in a web app?

  - by yoda

  Hi all, I've encountered this discussion related to FK's and web applications. Basically some people say that FK's in web applications doesn't represent a real improvement and can even make the application slower in some cases. What do you guys think, what's your experience? -- A quote from Heikki Tuuri, creator of InnoDB engine, founder and CEO of Innobase: InnoDB checks foreign keys as soon as a row is updated, no batching is performed or checks delayed till transaction commit Foreign keys are often serious performance overhead, but help maintain data consistency Foreign Keys increase amount of row level locking done and can make it spread to a lot of tables besides the ones directly updated

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• Data Modeling Help - Do I add another table, change existing table's usage, or something else?

  - by StackOverflowNewbie

  Assume I have the following tables and relationships: Person - Id (PK) - Name A Person can have 0 or more pets: Pet - Id (PK) - PersonId (FK) - Name A person can have 0 or more attributes (e.g. age, height, weight): PersonAttribute _ Id (PK) - PersonId (FK) - Name - Value PROBLEM: I need to represent pet attributes, too. As it turns out, these pet attributes are, in most cases, identical to the attributes of a person (e.g. a pet can have an age, height, and weight too). How do I represent pet attributes? Do I create a PetAttribute table? PetAttribute Id (PK) PetId (FK) Name Value Do I change PersonAttribute to GenericAttribute and have 2 foreign keys in it - one connecting to Person, the other connecting to Pet? GenericAttribute Id (PK) PersonId (FK) PetId (FK) Name Value NOTE: if PersonId is set, then PetId is not set. If PetId is set, PersonId is not set. Do something else?

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• Monitoring for non-pgp files

  - by Aheho

  For privacy reasons, I want to prevent my users from posting unencrypted files to my ftp site. It is company policy that all data exchanges of sensitive data be encrypted with PGP. I'd like to setup a program to monitor the ftp folders and whenever a new file is placed there, verify that it is in fact encrypted. I can't just rely on the file extension because in some cases, our trading partners require a specific filename that doesn't have a .PGP on the end. Is there a library or another method I can use to verify that a given file is encrypted? I'm using C# and .NET on a windows platform.

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• Basic question about request queues in IIS / ASP.Net

  - by larryq

  I have an ASP.Net application running under IIS 6. A simple page has two radio buttons and a submit button. If I select radio button "A" and submit the page, a lengthy PDF file is generated, which takes about a minute to build. If I select radio button "B", a small PDF is generated. (In both cases the PDF is written out to the Response object and it opens in my browser.) If I select radio button "A" and submit, then hit the red X in my browser to stop the current request, then select radio button "B" and resubmit, the page still takes a long time to process my request. No doubt my first request is still being processed on the server, but I was wondering how IIS and/or ASP.Net are queuing my requests so that fair server use is guaranteed among all users. Am I roughly correct in assuming something like this happens, and if so, how is it done?

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• Is hardware accelerated CSS3 in Safari 4 & 5 broken, or my CSS and JS?

  - by Dan Forys

  Hi all, I've created a somewhat silly site that shows you the expected weather forecast for any city in the World. On webkit based browsers, when the weather is sunny a sun with CSS3 animated rotated sunbeams appears. This works fine on Chrome. An example (sunny, at the moment) page is: http://willitraintoday.co.uk/iceland/reykjavik/ However, when viewed in Safari 4 or 5 on Mac Snow Leopard, when the sun appears the sky background appears over it. Weirder still, as the cloud containing the advert moves across the sky, it squashes the main text. When the cloud reaches the left edge, the text appears wider than normal and starts squashing down again. I've tried: - Disabling the CSS3 animation; it works fine in Safari - Juggling the z-index of various elements; to no avail Is there something up with my Javascript or CSS, or is the hardware accelerated snow leopard Safari broken in this case? It seems not to happen in Safari 4 on Leopard, but I don't have Leopard any more to test myself. Grateful for any opinions!

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• Unit testing a SQL code generator

  - by Tom H.

  The team I'm on is currently writing code in TSQL to generate TSQL code that will be saved as scripts and later run. We're having a little difficulty in separating our unit tests between testing the code generator parts and testing the actual code that they generate. I've read through another similar question, but I was hoping to get some specific examples of what kind of unit test cases we might have. As an example, let's say that I have a bit of code that simply generates a DROP statement for a view, given the view schema and name. Do I just test that the generated code matches some expected outcome using string comparisons and then in a later integration or system test make sure that the drop actually drops the view if it exists, does nothing if the view doesn't exist, or raises an error if the view is one that we are marking as not allowing a drop? Thanks for any advice!

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• How to create closed areas (convex polygons) from set of line segments ?

  - by Marten

  The following problem is in 2D, so some simplifications can be made when suggesting answers. I need to create closed areas (defined either by line segments or just set of points - convex polygon) from a set of points/line segments. Basically I used Voronoi to generate "roads". Then I changed some of the data. Now I need a way to loop through that data (which is still line segments but doesn't comply with Voronoi anymore) and generate "neigbourhoods" that are bordered with the "roads". I looked at some graph diagrams and shortest path theories, but I could not figure it out. Logically it could be done by starting at left edge from one point, finding the way back to that point using the shortest path with available lines (using only clockwise directions). Then mark this line set down and remove from the data. Then you can repeat the same process and get all the areas like that. I tried to implement that but it did not get me anywhere as I could not figure out a way to write a C++ code that could do that. Problem was with choosing the most counterclockwise line from available lines from a specific point. All angle based math I did gave wrong answers because the way sin/cos are implemented in c++. So to summarize - if you can help me with a totally new approach to the problem its good, if not could you help me find a way to write the part of the code that finds the shortest clockwise path back to the beginning point using the line segment set as paths back. Thank you for your help!

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• 2D Platformer Collision Problems With Both Axes

  - by AusGat

  I'm working on a little 2D platformer/fighting game with C++ and SDL, and I'm having quite a bit of trouble with the collision detection. The levels are made up of an array of tiles, and I use a for loop to go through each one (I know it may not be the best way to do it, and I may need help with that too). For each side of the character, I move it one pixel in that direction and check for a collision (I also check to see if the character is moving in that direction). If there is a collision, I set the velocity to 0 and move the player to the edge of the tile. My problem is that if I check for horizontal collisions first, and the player moves vertically at more than one pixel per frame, it handles the horizontal collision and moves the character to the side of the tile even if the tile is below (or above) the character. If I handle vertical collision first, it does the same, except it does it for the horizontal axis. How can I handle collisions on both axes without having those problems? Is there any better way to handle collision than how I'm doing it?

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• ArrayList<String> NullPointerException

  - by Carlucho

  Am trying to solve a labyrinth by DFS, using adj List to represent the vertices and edges of the graph. In total there are 12 nodes (3 rows[A,B,C] * 4 cols[0,..,3]). My program starts by saving all the vertex labels (A0,..C3), so far so good, then checks the adjacent nodes, also no problems, if movement is possible, it proceeds to create the edge, here its where al goes wrong. adjList[i].add(vList[j].label); I used the debugger and found that vList[j].label is not null it contains a correct string (ie. "B1"). The only variables which show null are in adjList[i], which leads me to believe i have implemented it wrongly. this is how i did it. public class GraphList { private ArrayList<String>[] adjList; ... public GraphList(int vertexcount) { adjList = (ArrayList<String>[]) new ArrayList[vertexCount]; ... } ... public void addEdge(int i, int j) { adjList[i].add(vList[j].label); //NULLPOINTEREXCEPTION HERE } ... } I will really appreaciate if anyone can point me on the right track regrading to what its going wrong... Thanks!

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• Remove trailing slash from comment form

  - by Sergio Vargott

  and i really need a code to remove the ending slash when a user put their link. for example i need them to put their url to grab their avatar, but in some cases they put their url ending with a slash (.com/) how can i remove that slash automatically? because when they put their url like that the avatar doesn't show i need them to end like this (.com) in order to show their avatar. I was looking for a remove trailing slash php code, but any solution will be appreciated. i tried to use this code but didn't work $string = rtrim($string, '/');

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• Simulating C-style for loops in python

  - by YGA

  (even the title of this is going to cause flames, I realize) Python made the deliberate design choice to have the for loop use explicit iterables, with the benefit of considerably simplified code in most cases. However, sometimes it is quite a pain to construct an iterable if your test case and update function are complicated, and so I find myself writing the following while loops: val = START_VAL while <awkward/complicated test case>: # do stuff ... val = <awkward/complicated update> The problem with this is that the update is at the bottom of the while block, meaning that if I want to have a continue embedded somewhere in it I have to: use duplicate code for the complicated/awkard update, AND run the risk of forgetting it and having my code infinite loop I could go the route of hand-rolling a complicated iterator: def complicated_iterator(val): while <awkward/complicated test case>: yeild val val = <awkward/complicated update> for val in complicated_iterator(start_val): if <random check>: continue # no issues here # do stuff This strikes me as waaaaay too verbose and complicated. Do folks in stack overflow have a simpler suggestion?

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• stop background of iphone webapp from responding to swipes

  - by JoeS

  I'm making a mobile version of my website, and trying to make it feel as native as possible on the iphone. However, any background areas of the page respond to swiping gestures such that you can shift the page partway off the screen. Specifically, if the user touches and swipes left, for example, the content shifts off the edge of the screen and one can see a gray background 'behind' the page. How can this be prevented? I'd like to have the page itself be 320x480 with scroll-swiping disabled (except on list elements that I choose). I have added the following meta tags to the top of the page: <meta name="viewport" content="width=320; height=480; initial-scale=1.0; maximum-scale=1.0; user-scalable=0;"/> <meta name="apple-mobile-web-app-capable" content="yes" /> <meta name="apple-mobile-web-app-status-bar-style" content="black" /> I've also tried the following as the event handler for the touchstart, touchmove, and touchend events of the body element: function cancelTouchEvent(e) { if (!e) var e = window.event; e.cancelBubble = true; if (e.stopPropagation) e.stopPropagation(); if (e.preventDefault) e.preventDefault(); return false; } It doesn't stop the swiping behavior, but does prevent clicks on all links on the page... Any help is much appreciated. Thanks!

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• matplotlib.pyplot, preserve aspect ratio of the plot

  - by Headcrab

  Assuming we have a polygon coordinates as polygon = [(x1, y1), (x2, y2), ...], the following code displays the polygon: import matplotlib.pyplot as plt plt.fill(*zip(*polygon)) plt.show() By default it is trying to adjust the aspect ratio so that the polygon (or whatever other diagram) fits inside the window, and automatically changing it so that it fits even after resizing. Which is great in many cases, except when you are trying to estimate visually if the image is distorted. How to fix the aspect ratio to be strictly 1:1? (Not sure if "aspect ratio" is the right term here, so in case it is not - I need both X and Y axes to have 1:1 scale, so that (0, 1) on both X and Y takes an exact same amount of screen space. And I need to keep it 1:1 no matter how I resize the window.)

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