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• Dealing With Java Default Level Access Specifiers

  - by Tom Tresansky

  I've seen some code in a project recently where some fields in a couple classes have been using the default access modifier without good reason to. It almost looks like a case of "oops, forgot to make these private". Since the classes are used almost exclusively outside of the package they are defined in, the fields are not visible from the calling code, and are treated as private. So the mistake/oversight would not be very noticeable. However, encapsulation is broken. If I wanted to add a new class to the existing package, I could then mess with internal data in objects using fields with default access. So, my questions: Are there any best practices concerning default access specifiers that I should be aware of? Anything that would help prevent this type of accident from re-occurring? Are are any annotations which might say something to the effect of "I really meant for these to be default access"? Using CheckStyle, or any other Eclipse plugins, is there any way to flag instances of default fields, or disallow any not accompanied by, say, a "//default access" comment trailing them?

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• Help! Getting an error copying the data from one column to the same column in a similar recordset..

  - by Mike D

  I have a routine which reads one recordset, and adds/updates rows in a similar recordset. The routine starts off by copying the columns to a new recordset: Here's the code for creating the new recordset.. For X = 1 To aRS.Fields.Count mRS.Fields.Append aRS.Fields(X - 1).Name, aRS.Fields(X - 1).Type, aRS.Fields(X - _ 1).DefinedSize, aRS.Fields(X - 1).Attributes Next X Pretty straight forward. Notice the copying of the name, Type, DefinedSize & Attributes... Further down in the code, (and there's nothing that modifies any of the columns between.. ) I'm copying the values of a row to a row in the new recordset as such: For C = 1 To aRS.Fields.Count mRS.Fields(C - 1) = aRS.Fields(C - 1) Next C When it gets to the last column which is a numeric, it craps with the "Mutliple-Step Operation Generated an error" message. I know that MS says this is an error generated by the provider, which in this case is ADO 2.8. There is no open connect to the DB at this point in time either. I'm pulling what little hair I have left over this one... (and I don't really care at this point that the column index is 'X' in one loop & 'C' in the other... I'll change it later when I get the real problem fixed...)

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• MSI install sequence - run DB scripts before services start

  - by marc_s

  Folks, we're running into some sequencing troubles with our MSI install. As part of our app, we install a bunch of services and allow the user to pick whether to start them right away or later. When they start right away, they seem to start too early in the install sequence - before our database manager had a chance to update the database. Right now, our custom action to run the database updater looks like this - it's being run after "InstallFinalize" - very late in the process. <InstallExecuteSequence> <RemoveExistingProducts After='InstallInitialize' /> <Custom Action='RunDbUpdateManagerAction' After='InstallFinalize'> DbUpdateManager=3</Custom> </InstallExecuteSequence> What would be the more appropriate step to run after or before, to make sure the DB scripts are executed before any of the installed services start up? Is there a "BeforeServiceStart" step? EDIT: Just defining the "Before='StartServices'" attribute on the tag didn't solve my problem. I am assuming the issue is this: the custom action has an "inner text", which represents a condition, and this condition is: "&DbUpdateManager=3". From what I can deduce from trial & error, this probably means "the DbUpdateManager feature must be published". Now, trouble is: "PublishFeature" comes way at the end in the install sequence, just before "InstallFinalize", and definitely AFTER InstallServices / StartServices. So when I specify the "Before=StartServices" requirement, the condition "DbUpdateManager feature must be published" isn't true yet, so the DbUpdateManager doesn't get executed :-( I tried removing the condition - in that case, my DbUpdateManager sometimes doesn't execute at all, sometimes more than once - no real clear pattern as to what happens when..... Any more ideas?? Is there a way I could check for a condition "the DbUpdateManager feature is installed" which would be true after the "InstallFiles" step?? Marc

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• FFT and IFFT on 3D matrix (Matlab)

  - by SteffenDM

  I have a movie with 70 grayscale frames in MATLAB. I have put them in a 3-D matrix, so the dimensions are X, Y and time. I want to determine the frequencies in the time dimension, so I have to calculate the FFT for every point in the 3rd dimension. This is not a problem but I have to return the images to the original form with ifft. In a normal situation this would be true: X = ifft(fft(X)), but this is not the case it seems in MATLAB when you work with multidimensional data. This is the code I use: for i = 1:length y(:, :, i) = [img1{i, level}]; %# take each picture from an cell array and put it end %# and put it in 3D array y2 = ifft(fft(y, NFFT,3), NFFT, 3); %# NFFT = 128, the 3 is the dimension in which i want %# to calculate the FFT and IFFT y is 480x640x70, so there are 70 images of 640x480 pixels. If I use only fft, y2 is 480x640x128 (this is normal because we want 128 points with NFFT). If I use fft and ifft, y2 is 480x640x128 pixels. This is not normal, the 128 should be 70 again. I tried to do it in just one dimension by using 2 for loops and this works fine. The for loops take to much time, though.

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• design pattern for related inputs

  - by curiousMo

  My question is a design question : let's say i have a data entry web page with 4 drop down lists, each depending on the previous one, and a bunch of text boxes. ddlCountry (DropDownList) ddlState (DropDownList) ddlCity (DropDownList) ddlBoro (DropDownList) txtAddress (TxtBox) txtZipcode(TxtBox) and an object that represents a datarow with a value for each: countrySeqid stateSeqid citySeqid boroSeqid address zipCode naturally the country, state, city and boro values will be values of primary keys of some lookup tables. when the user chooses to edits that record, i would load it from database and load it into the page. the issue that I have is how to streamline loading the DropDownLists. i have some code that would grab the object,look thru its values and move them to their corresponding input controls in one shot. but in this case i will have to load the ddlCountry with possible values, then assign values, then do the same thing for the rest of the ddls. I guess i am looking for an elegant solution. i am using asp.net, but i think it is irrelevant to the question. i am looking more into a design pattern.

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• Using Relative Paths to Load Resources in Cocoa/C++

  - by moka

  I am currently working directly with Cocoa for the first time to built a screen saver. Now I came across a problem when trying to load resources from within the .saver bundle. I basically have a small C++ wrapper class to load .exr files using freeImage. This works as long as I use absoulte paths, but that's not very useful, is it? So, basically, I tried everything: putting the .exr file at the level of the .saver bundle itself, inside the bundles Resources folder, and so on. Then I simply tried to load the .exr like this, but without success: particleTex = [self loadExrTexture:@"ball.exr"]; I also tried making it go to the .saver bundles location like this: particleTex = [self loadExrTexture:@"../../../ball.exr"]; ...to maybe load the .exr from that location, but without success. I then came across this: NSString * path = [[NSBundle mainBundle] pathForResource:@"ball" ofType:@"exr"]; const char * pChar = [path UTF8String]; ...which seems to be a common way to find resources in Cocoa, but for some reason it's empty in my case. Any ideas about that? I really tried out anything that came to my mind without success so I would be glad about some input!

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• Which class should store the lookup table?

  - by max

  The world contains agents at different locations, with only a single agent at any location. Each agent knows where he's at, but I also need to quickly check if there's an agent at a given location. Hence, I also maintain a map from locations to agents. I have a problem deciding where this map belongs to: class World, class Agent (as a class attribute) or elsewhere. In the following I put the lookup table, agent_locations, in class World. But now agents have to call world.update_agent_location every time they move. This is very annoying; what if I decide later to track other things about the agents, apart from their locations - would I need to add calls back to the world object all across the Agent code? class World: def __init__(self, n_agents): # ... self.agents = {} self.agent_locations = {} for id in range(n_agents): x, y = self.find_location() agent = Agent(self,x,y) self.agents.append(agent) self.agent_locations[x,y] = agent def update_agent_location(self, agent, x, y): del self.agent_locations[agent.x, agent.y] self.agent_locations[x, y] = agent def update(self): # next step in the simulation for agent in self.agents: agent.update() # next step for this agent # ... class Agent: def __init__(self, world, x, y): self.world = world self.x, self.y = x, y def move(self, x1, y1): self.world.update_agent_location(self, x1, y1) self.x, self.y = x1, y1 def update(): # find a good location that is not occupied and move there for x, y in self.valid_locations(): if not self.location_is_good(x, y): continue if self.world.agent_locations[x, y]: # location occupied continue self.move(x, y) I can instead put agent_locations in class Agent as a class attribute. But that only works when I have a single World object. If I later decide to instantiate multiple World objects, the lookup tables would need to be world-specific. I am sure there's a better solution... EDIT: I added a few lines to the code to show how agent_locations is used. Note that it's only used from inside Agent objects, but I don't know if that would remain the case forever.

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• Listening socket

  - by hoodoos

  I got a strange problem, I never actually expirienced this before, here is the code of the server (client is firefox in this case), the way I create it: _Socket = new Socket( AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp ); _Socket.Bind( new IPEndPoint( Settings.IP, Settings.Port ) ); _Socket.Listen( 1000 ); _Socket.Blocking = false; the way i accept connection: while( _IsWorking ) { if( listener.Socket.Poll( -1, SelectMode.SelectRead ) ) { Socket clientSocket = listener.Socket.Accept(); clientSocket.Blocking = false; clientSocket.SetSocketOption( SocketOptionLevel.Tcp, SocketOptionName.NoDelay, true ); } } So I'm expecting it hang on listener.Socket.Poll till new connection comes, but after first one comes it hangs on poll forever. I tried to poll it constantly with smaller delay, let's say 10 microseconds, then it never goes in SelectMode.SelectRead. I guess it maybe somehow related on client's socket reuse? Maybe I don't shutdown client socket propertly and client(firefox) decides to use an old socket? I disconnect client socket this way: Context.Socket.Shutdown( SocketShutdown.Both ); // context is just a wrapper around socket Context.Socket.Close(); What may cause that problem?

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• Execute a function to affect different template class instances

  - by Samer Afach

  I have a complicated problem, and I need help. I have a base case, class ParamBase { string paramValue; //... } and a bunch of class templates with different template parameters. template <typename T> class Param : public ParamBase { T value; //... } Now, each instance of Param has different template parameter, double, int, string... etc. To make it easier, I have a vector to their base class pointers that contains all the instances that have been created: vector<ParamBase*> allParamsObjects; The question is: How can I run a single function (global or member or anything, your choice), that converts all of those different instances' strings paramValue with different templates arguments and save the conversion result to the appropriate type in Param::value. This has to be run over all objects that are saved in the vector allParamsObjects. So if the template argument of the first Param is double, paramValue has to be converted to double and saved in value; and if the second Param's argument is int, then the paramValue of the second has to be converted to int and saved in value... etc. I feel it's almost impossible... Any help would be highly appreciated :-)

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• How to do an additional search on archive in rails if record not found, by extending model?

  - by Nick Gorbikoff

  Hello, I was wondering if somebody knows an elegant solution to the following: Suppose I have a table that holds orders, with a bunch of data. So I'm at 1M records, and searches begin to take time. So I want to speed it up by archiving some data that is more than 3 years old - saving it into a table called orders-archive, and then purging them from the orders table. So if we need to research something or customer wants to pull older information - they still can, but 99% of the lookups are done on the orders no older than a year and a half - so there is no reason to keep looking through older data all the time. These move & purge operations can be then croned to be done on a weekly basis. I already did some tests and I know that I will slash my search times by about 4 times. So far so good, right? However I was thinking about how to implement older archival lookups and the only reasonable thing I can think of is some sort of if-else If not found in orders, do a search in orders-archive. However - I have about 20 tables that I want to archive and god knows how many searches / finds are done through out the code, that I don't want to modify. So I was wondering if there is an elegant rails-way solution to this problem, by extending a model somehow? Has anyone dealt with similar case before? Thank you.

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• C++ MACRO that will execute a block of code and a certain command after that block.

  - by Poni

  void main() { int xyz = 123; // original value { // code block starts xyz++; if(xyz < 1000) xyz = 1; } // code block ends int original_value = xyz; // should be 123 } void main() { int xyz = 123; // original value MACRO_NAME(xyz = 123) // the macro takes the code code that should be executed at the end of the block. { // code block starts xyz++; if(xyz < 1000) xyz = 1; } // code block ends << how to make the macro execute the "xyz = 123" statement? int original_value = xyz; // should be 123 } Only the first main() works. I think the comments explain the issue. It doesn't need to be a macro but to me it just sounds like a classical "macro-needed" case. By the way, there's the BOOST_FOREACH macro/library and I think it does the exact same thing I'm trying to achieve but it's too complex for me to find the essence of what I need. From its introductory manual page, an example: #include <string> #include <iostream> #include <boost/foreach.hpp> int main() { std::string hello( "Hello, world!" ); BOOST_FOREACH( char ch, hello ) { std::cout << ch; } return 0; }

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• [C#]How to introduce retry logic into LINQ to SQL to deal with timeouts?

  - by codemonkie

  I need to find ways to add retry mechanism to my DB calls in case of timeouts, LINQ to SQL is used to call some sprocs in my code... using (MyDataContext dc = new MyDataContext()) { int result = -1; //denote failure int count = 0; while ((result < 0) && (count < MAX_RETRIES)) { result = dc.myStoredProc1(...); count++; } result = -1; count = 0; while ((result < 0) && (count < MAX_RETRIES)) { result = dc.myStoredProc2(...); count++; } ... ... } Not sure if the code above is right or posed any complications. It'll be nice to throw an exception after MAX_RETRIES has reached, but I dunno how and where to throw them appropriately :-) Any helps appreciated.

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• hosting a high traffic facebook app (game)

  - by z3cko

  we are currently developing a high traffic facebook application. all the traffic will be within one month, where there are 500.000 to 1.000.000 expected users. after that month, the game is over and we have a winner - so the app will be archived. we are currently planning to develop the application with ruby on rails and searching for hosting options that can deal with the traffic. the problem is not so much the users, but the peak values: we will have around 500.000 requests coming daily within a short timeframe (lets say within 3 minutes in the worst case) we are expecting 500.000 to 1.000.000 users of the application, with peaks at 1:00pm (timezone GMT+1), where most (up to 80% of the users) will send most of the requests. the requests are from 11th of june to 11.july - after that, the app/game is closed/over. we are currently developing an aggressive caching mechanism - currently we are thinking about 2 or 3 small apps/webservices, that will handle the load. the load is distributed as follows: a) main application, cached data (11 screens, 200k each) b) voting: every day until 1:00pm (timezone GMT+1) - every user votes with about 10k data sent, high concurrent peak values! questions: is there any specific application setup that is recommendable? are there any hosting partners that can be recommended? thanks!

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• Possible to Dynamic Form Generation Using PHP global variables

  - by J M 4

  I am currently a fairly new programmer but am trying to build a registration page for a medical insurance idea we have which captures individual information and subsequent pieces of information about that individual's sub parts. In this case, it is a fight promoter enrolling his 15+ boxers for fight testing services. Right now, I have the site fully laid out to accept 7 fighters worth of information. This is collected during the manager's enrollment. However, each fighter's information is passed and stored in session super globals such as: $_SESSION['F1Firstname']; and $_SESSION['F3SSN3'];. The issue I am running into is this, I want to create a drop down menu selector for the manager to add information for up to 20-30 fighters. Right now I use PHP to state: if ($_SESSION['Num_Fighters'] 6) ... then display the table form fields to collect consumer data. If I have to build hidden elements for 30 fighters AND provide javascript/php validation (yes I am doing both) then I fear the file size for the document will be unnecessarily large for the maanger who only wants to enroll 2 fighters. Can anybody help?

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• Sync two SqlExpress using NHibernate

  - by Christian

  Hello, I am creating a simple project management system which uses NHibernate for object storage. The underlying database is SQL express (at least currently for development). The client runs on either the desktop or laptop. I know I could use web-services and store the DB only on the desktop, but this would force the desktop to be available all the time. I am currently thinking about duplicating the DB, having two instances with "different data". To clarify, we are not talking about a productive app here, its a prototype. One way to achieve this very simple would be the following process: Client: Check if desktop DB is available (through web service) Client: If yes, use desktop storage, no problem here Client: If not, use own DB as storage Client: Poll desktop regulary, as soon as it comes on, sync Client: Switch to desktop storage ... Desktop: Do not attempt any DB operation before checking for required sync Desktop: If sync needed, do it... My question is now, how would you sync? Assume 4 or 5 types of objects, all have GUID as identifiers. Would you always manually "lazy load" all objects of a certain type and feed them to the DB. Would you always drop the whole desktop DB in case the client DB may be newer and out of sync? Again, I want to stress out, I am not assuming any conflicts or stale data, I basically just want to "copy the whole DB from the client". Would you use NHibernate for this? Or would you separate the copy process? When I think about it, my questions comes down to this: Is there any function from NHibernate: SyncDBs_SourceWins_(SourceDB, TargetDB) Thanks for help, Chris

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• Open closed prinicple, problem

  - by Marcus

  Hi, I'm trying to apply OCP to a code snippet I have that in it's current state is really smelly, but I feel I'm not getting all the way to the end. Current code: public abstract class SomeObject {} public class SpecificObject1 : SomeObject {} public class SpecificObject2 : SomeObject {} // Smelly code public class Model { public void Store(SomeObject someObject) { if (someObject is SpecificObject1) {} else if (someObject is SpecificObject2) {} } } That is really ugly, my new approach looks like this: // No so smelly code public class Model { public void Store(SomeObject someObject) { throw new Expception("Not allowed!"); } public void Store(SpecificObject1 someObject) {} public void Store(SpecificObject2 someObject) {} } When a new SomeObject type comes along I must implement how that specific object is stored, this will break OCP cause I need to alter the Model-class. To move the store logic to SomeObject also feels wrong cause then I will violate SRP (?), becuase in this case the SomeObject is almost like a DTO, it's resposibility it not how to know to store itself. If a new implementation to SomeObject comes along who's store implementation is missing I will get a runtime error due to exception in Store method in Model class, it also feels like a code smell. This is because calling code will in the form of IEnumerable<SomeObject> sequence; I will not know the specific types of the sequence objects. I can't seem to grasp the OCP-concept. Anyone has any concrete examples or links that is a bit more than just some Car/Fruit example?

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• How to use db4o IObjectContainer in a web application ? (Container lifetime ?)

  - by driis

  I am evaluating db4o for persistence for a ASP .NET MVC project. I am wondering how I should use the IObjectContainer in a web context with regards to object lifetime. As I see it, I can do one of the following: Create the IObjectContainer at application startup and keep the same instance for the entire application lifetime. Create one IObjectContainer per request. Start a server, and get a client IObjectContainer for each database interaction. What are the implications of these options, in terms of performance and concurrency ? Since the database is locked when an IObjectContainer is opened, I am pretty sure that option 2) would get me some problems with concurrency - would this also be the case for option 1 ? As I understand it, if I retrieve an object from an IObjectContainer, it must be saved by the same IObjectContainer instance - in order for db4o to identify it as being the same object. Therefore, If I choose option 3), I would have to retrieve the original object, make the necessary changes (copy data from a modified object), and then store it using the same IObjectContainer. Is this true ?

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• Sorcery/Capybara: Cannon log in with :js => true

  - by PlankTon

  I've been using capybara for a while, but I'm new to sorcery. I have a very odd problem whereby if I run the specs without Capybara's :js = true functionality I can log in fine, but if I try to specify :js = true on a spec, username/password cannot be found. Here's the authentication macro: module AuthenticationMacros def sign_in user = FactoryGirl.create(:user) user.activate! visit new_sessions_path fill_in 'Email Address', :with => user.email fill_in 'Password', :with => 'foobar' click_button 'Sign In' user end end Which is called in specs like this: feature "project setup" do include AuthenticationMacros background do sign_in end scenario "creating a project" do "my spec here" end The above code works fine. However, IF I change the scenario spec from (in this case) scenario "adding questions to a project" do to scenario "adding questions to a project", :js => true do login fails with an 'incorrect username/password' combination. Literally the only change is that :js = true. I'm using the default capybara javascript driver. (Loads up Firefox) Any ideas what could be going on here? I'm completely stumped. I'm using Capybara 2.0.1, Sorcery 0.7.13. There is no javascript on the sign in page and save_and_open_page before clicking 'sign in' confirms that the correct details are entered into the username/password fields. Any suggestions really appreciated - I'm at a loss.

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• Behavior difference between UIView.subviews and [NSView subviews]

  - by zpasternack

  I have a piece of code in an iPhone app, which removes all subviews from a UIView subclass. It looks like this: NSArray* subViews = self.subviews; for( UIView *aView in subViews ) { [aView removeFromSuperview]; } This works fine. In fact, I never really gave it much thought until I tried nearly the same thing in a Mac OS X app (from an NSView subclass): NSArray* subViews = [self subviews]; for( NSView *aView in subViews ) { [aView removeFromSuperview]; } That totally doesn’t work. Specifically, at runtime, I get this: *** Collection <NSCFArray: 0x1005208a0> was mutated while being enumerated. I ended up doing it like so: NSArray* subViews = [[self subviews] copy]; for( NSView *aView in subViews ) { [aView removeFromSuperview]; } [subViews release]; That's fine. What’s bugging me, though, is why does it work on the iPhone? subviews is a copy property: @property(nonatomic,readonly,copy) NSArray *subviews; My first thought was, maybe @synthesize’d getters return a copy when the copy attribute is specified. The doc is clear on the semantics of copy for setters, but doesn’t appear to say either way for getters (or at least, it’s not apparent to me). And actually, doing a few tests of my own, this clearly does not seem to be the case. Which is good, I think returning a copy would be problematic, for a few reasons. So the question is: how does the above code work on the iPhone? NSView is clearly returning a pointer to the actual array of subviews, and perhaps UIView isn’t. Perhaps it’s simply an implementation detail of UIView, and I shouldn’t get worked up about it. Can anyone offer any insight?

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• Import & modify date data in MATLAB

  - by niko

  I have a .csv file with records written in the following form: 2010-04-20 15:15:00,"8.9915176259e+00","8.8562623697e+00" 2010-04-20 15:30:00,"8.5718021723e+00","8.6633827160e+00" 2010-04-20 15:45:00,"8.4484844117e+00","8.4336586330e+00" 2010-04-20 16:00:00,"1.1106980342e+01","8.4333062208e+00" 2010-04-20 16:15:00,"9.0643470589e+00","8.6885660103e+00" 2010-04-20 16:30:00,"8.2133517943e+00","8.2677822671e+00" 2010-04-20 16:45:00,"8.2499419380e+00","8.1523501983e+00" 2010-04-20 17:00:00,"8.2948492278e+00","8.2884797924e+00" From these data I would like to make clusters - I would like to add a column with number indicating the hour - so in case of the first row a value 15 has to be added in a new row. The first problem is that calling a function [numData, textData, rawData] = xlsread('testData.csv') creates an empty matrix numData and one-column textData and rawData structures. Is it possible to create any template which recognizes a yyyy, MM, dd, hh, mm, ss values from the data above? What I would basically like to do with these data is to categorize the values by hours so from the example row of input: 2010-04-20 15:15:00,"8.9915176259e+00","8.8562623697e+00" update 1: in Matlab the line above is recognized as a string: '2010-04-26 13:00:00,"1.0428104753e+00","2.3456394130e+00"' I would want this to be the output: 15, 8.9915176259e+00, 8.8562623697e+00 update 1: a string has to be parsed Does anyone know how to parse a string and retrieve a timestamp, value1 (1.0428104753e+00) and value2 (2.3456394130e+00) from it as separate values?

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• IndexOutOfRangeException when a stream is a multiple of the buffer size

  - by dnord

  I don't have a lot of experience with streams and buffers, but I'm having to do it for a project, and I'm stuck on an exception being thrown when the stream I'm reading is a multiple of the buffer size I've chosen. Let me show you: My code starts by reading bufferSize (100, let's say) bytes from the stream: numberOfBytesRead = DataReader.GetBytes(0, index, output, 0, bufferSize); Then, I loop through a while loop: while (numberOfBytesRead == bufferSize) { BufferWriter.Write(output); BufferWriter.Flush(); index += bufferSize; numberOfBytesRead = DataReader.GetBytes(0, index, output, 0, bufferSize); } ... and, once we get to a non-bufferSize read, we know we've hit the end of the stream and can move on. But if the bufferSize is 100, and the stream is 200, we'll read positions 0-99, 100-199, and then the attempt to read 200-299 errors out. I'd like it if it returned 0, but it throws an error. What I'm doing to handle that is, well, a try-catch: catch (System.IndexOutOfRangeException) numberOfBytesRead = 0; ...which ends the loop, and successfully finishes the thing, but we all know I don't want to control code flow with error handling. Is there a better (more standard?) way to handle stream reading when the stream length is unknown? This seems like a small wrinkle in a fairly reasonable strategy for reading streams, but I just don't know if I've got it wrong or what. The specifics of this (which I've cleaned up a little bit for posting) are a MySqlDataReader hitting a LARGEBLOB column. It's working whenever the buffer is larger than the number of returned bytes, or when the number of returned bytes is not a multiple of bufferSize. Because we don't, in that case, throw an IndexOutOfRangeException.

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• Findbugs and comparing

  - by Rob Goodwin

  I recently started using the findbugs static analysis tool in a java build I was doing. The first report came back with loads of High Priority warnings. Being the obsessive type of person, I was ready to go knock them all out. However, I must be missing something. I get most of the warnings when comparing things. Such as the following code: public void setSpacesPerLevel(int value) { if( value >= 0) { ... produces a high priority warning at the if statement that reads. File: Indenter.java, Line: 60, Type: BIT_AND_ZZ, Priority: High, Category: CORRECTNESS Check to see if ((...) & 0) == 0 in sample.Indenter.setSpacesPerLevel(int) I am comparing an int to an int, seems like a common thing. I get quite a few of that type of error with similar simple comparisons. I have alot of other high priority warnings on what appears to be simple code blocks. Am I missing something here? I realize that static analysis can produce false positives, but the errors I am seeing seem too trivial of a case to be a false positive. This one has me scratching my head as well. for(int spaces = 0;spaces < spacesPerLevel;spaces++){... Which gives the following findbugs warning: File: Indenter.java, Line: 160, Type: IL_INFINITE_LOOP, Priority: High, Category: CORRECTNESS There is an apparent infinite loop in sample.Indenter.indent() This loop doesn't seem to have a way to terminate (other than by perhaps throwing an exception). Any ideas? So basically I have a handful of files and 50-60 high priority warnings similar to the ones above. I am using findbugs 1.3.9 and calling it from the findbugs ant task

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• SQL: How to Return One DB Row from Two That Have The Same Values In Opposite Columns Using the MAX F

  - by OneSource

  Hi, This is what I'm trying to do. I have three columns in a table - ID, Column1, Column2 - with this example data: ID Column1 Column2 1     1            2 2     2            1 3     4            3 4     3            4 Since, in the first two rows, Column1 and Column2 have the same values (but in different columns), I want my MAX query to return an ID of 2. Same thing with rows 3 and 4 .... since Columns 1 and 2 have the same values (but in different columns), I want MAX(ID) to return 4. Of course, with MAX, you use Group By, but that will not work in my case. In effect, I need a Group By to work across two columns. Is this possible? If not, what's the best way to accomplish getting the IDs of 2 and 4 given the matching values that are in different columns? Thanks!

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• Request for advice about class design, inheritance/aggregation

  - by Lasse V. Karlsen

  I have started writing my own WebDAV server class in .NET, and the first class I'm starting with is a WebDAVListener class, modelled after how the HttpListener class works. Since I don't want to reimplement the core http protocol handling, I will use HttpListener for all its worth, and thus I have a question. What would the suggested way be to handle this: Implement all the methods and properties found inside HttpListener, just changing the class types where it matters (ie. the GetContext + EndGetContext methods would return a different class for WebDAV contexts), and storing and using a HttpListener object internally Construct WebDAVListener by passing it a HttpListener class to use? Create a wrapper for HttpListener with an interface, and constrct WebDAVListener by passing it an object implementing this interface? If going the route of passing a HttpListener (disguised or otherwise) to the WebDAVListener, would you expose the underlying listener object through a property, or would you expect the program that used the class to keep a reference to the underlying HttpListener? Also, in this case, would you expose some of the methods of HttpListener through the WebDAVListener, like Start and Stop, or would you again expect the program that used it to keep the HttpListener reference around for all those things? My initial reaction tells me that I want a combination. For one thing, I would like my WebDAVListener class to look like a complete implementation, hiding the fact that there is a HttpListener object beneath it. On the other hand, I would like to build unit-tests without actually spinning up a networked server, so some kind of mocking ability would be nice to have as well, which suggests I would like the interface-wrapper way. One way I could solve this would be this: public WebDAVListener() : WebDAVListener(new HttpListenerWrapper()) { } public WebDAVListener(IHttpListenerWrapper listener) { } And then I would implement all the methods of HttpListener (at least all those that makes sense) in my own class, by mostly just chaining the call to the underlying HttpListener object. What do you think? Final question: If I go the way of the interface, assuming the interface maps 1-to-1 onto the HttpListener class, and written just to add support for mocking, is such an interface called a wrapper or an adapter?

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• Real time location tracking - windows program or browser based?

  - by mawg

  I want to track a few hundred, maybe a few thousand people in real time. Let's say that the hardware aspects are sorted out and I can get the data into a database. Now, I want to get it out and show it, in real-time. Weeeell ... "real-enough" time. Let's say that I want to draw a floorplan of a building and plot everyone every 1 to 5 seconds. (I might want to show only certain "kinds" of people at the click of a button; I will need datamining, etc, but let's stick with the worse case scenario). I am comfortable enough with PHP, though not this sort of thing. I personally would be happier with a windows app coded in Delphi, but the trend seems to be to make everything browser based. So, the question, I guess is whether a browser can handle this and whether there are compelling arguments for a windows-based or browser-based solution. If browser-based can handle this (displaying a few thousand data-points a second), and there are no overwhelming arguments for windows then I guess I will go for browser-based and learn a few new tricks. The obvious advantage being that I could also re-use a large part of my code for (vehicle) tracking on Google maps.

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