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• Best practice with respect to NPE and multiple expressions on single line

  - by JRL

  I'm wondering if it is an accepted practice or not to avoid multiple calls on the same line with respect to possible NPEs, and if so in what circumstances. For example: getThis().doThat(); vs Object o = getThis(); o.doThat(); The latter is more verbose, but if there is an NPE, you immediately know what is null. However, it also requires creating a name for the variable and more import statements. So my questions around this are: Is this problem something worth designing around? Is it better to go for the first or second possibility? Is the creation of a variable name something that would have an effect performance-wise? Is there a proposal to change the exception message to be able to determine what object is null in future versions of Java ?

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• How can I make this client as a multithread client?

  - by Johanna

  Hi, I have read a lot about multithread client but for this one,I can not make it multithread! would you please help me? public class MainClient implements Runnable{ private static InformationClass info = new InformationClass(); private static Socket c; private static String text; public static String getText() { return text; } public static void setText(String text) { MainClient.text = text; } private static PrintWriter os; private static BufferedReader is; static boolean closed = false; /** * @param args the command line arguments */ public static void main(String[] args) { MainFrame farme = new MainFrame(); farme.setVisible(true); try { c = new Socket("localhost", 5050); os = new PrintWriter(c.getOutputStream(), true); is = new BufferedReader(new InputStreamReader(c.getInputStream())); } catch (UnknownHostException ex) { Logger.getLogger(MainClient.class.getName()).log(Level.SEVERE, null, ex); } catch (IOException ex) { Logger.getLogger(MainClient.class.getName()).log(Level.SEVERE, null, ex); } } public static void active() { String teXt = MainClient.getText(); System.out.println(teXt); os.println(teXt); try { String line = is.readLine(); System.out.println("Text received: " + line); os.flush(); is.close(); is.close(); c.close(); } catch (IOException ex) { Logger.getLogger(MainClient.class.getName()).log(Level.SEVERE, null, ex); } } } also active method will be called when the client write something on the text area and then clicks on the send button. 2) also i have a question that: in the other class I have this action performed for my send button,does it mean that client is multithread?? private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { new Thread(new Runnable() { @Override public void run() { // This gets run in a background thread String text = jTextArea1.getText(); jTextArea2.append(client.getCurrentName() + " : " + text + "\n"); MainClient.setText(client.getCurrentName() + " : " + text + "\n"); clear(); MainClient.active(); } }).start(); } Last EDIT: this is my active method: public static void active() { String teXt = MainClient.getText(); os.println(teXt); String line = is.readLine(); System.out.println("Text received: " + line); os.flush(); is.close(); is.close(); c.close(); }

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• Can not access android /data folder?

  - by fonter

  try { Runtime rt = Runtime.getRuntime(); Process pcs = rt.exec("ls -l /data"); BufferedReader br = new BufferedReader(new InputStreamReader(pcs .getInputStream())); String line = null; while ((line = br.readLine()) != null) { Log.e("line","line="+line); } br.close(); pcs.waitFor(); int ret = pcs.exitValue(); Log.e("ret","ret="+ret); } catch (Exception e) { Log.e("Exception", "Exception", e); } only print "ret=0",How to print the correct path?

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• Large File Download - Connection With Server Reset

  - by daveywc

  I have an asp.net website that allows the user to download largish files - 30mb to about 60mb. Sometimes the download works fine but often it fails at some varying point before the download finishes with the message saying that the connection with the server was reset. Originally I was simply using Server.TransmitFile but after reading up a bit I am now using the code posted below. I am also setting the Server.ScriptTimeout value to 3600 in the Page_Init event. private void DownloadFile(string fname, bool forceDownload) { string path = MapPath(fname); string name = Path.GetFileName(path); string ext = Path.GetExtension(path); string type = ""; // set known types based on file extension if (ext != null) { switch (ext.ToLower()) { case ".mp3": type = "audio/mpeg"; break; case ".htm": case ".html": type = "text/HTML"; break; case ".txt": type = "text/plain"; break; case ".doc": case ".rtf": type = "Application/msword"; break; } } if (forceDownload) { Response.AppendHeader("content-disposition", "attachment; filename=" + name.Replace(" ", "_")); } if (type != "") { Response.ContentType = type; } else { Response.ContentType = "application/x-msdownload"; } System.IO.Stream iStream = null; // Buffer to read 10K bytes in chunk: byte[] buffer = new Byte[10000]; // Length of the file: int length; // Total bytes to read: long dataToRead; try { // Open the file. iStream = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read); // Total bytes to read: dataToRead = iStream.Length; //Response.ContentType = "application/octet-stream"; //Response.AddHeader("Content-Disposition", "attachment; filename=" + filename); // Read the bytes. while (dataToRead > 0) { // Verify that the client is connected. if (Response.IsClientConnected) { // Read the data in buffer. length = iStream.Read(buffer, 0, 10000); // Write the data to the current output stream. Response.OutputStream.Write(buffer, 0, length); // Flush the data to the HTML output. Response.Flush(); buffer = new Byte[10000]; dataToRead = dataToRead - length; } else { //prevent infinite loop if user disconnects dataToRead = -1; } } } catch (Exception ex) { // Trap the error, if any. Response.Write("Error : " + ex.Message); } finally { if (iStream != null) { //Close the file. iStream.Close(); } Response.Close(); } }

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• OpenGL Vertex Attributes - Normalisation

  - by Daniel

  Alas, I have searched, and have found no definitive answer. When would you normalize the vertex data in OpenGL using the following command: glVertexAttribPointer(index, size, type, normalize, stride, pointer); I.e when would normalize == GL_TRUE; what situations, and why would you choose to let the GPU do the calculations instead of preprocessing it? All examples I have ever seen, have this set to GL_FALSE; and I cannot personally see a use for it. But Khronos aren't stupid, so it must be there for something useful (and probably common).

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• How to load a configuration file at startup within tomcat

  - by Alex

  I want to be able to load my configuration for the webapp at startup of tomcat (apache commons configuration library) is this a possible way: public class MyAppCfg implements javax.servlet.ServletContextListener { private ServletContext context = null; @Override public void contextInitialized(ServletContextEvent event) { try{ this.context = event.getServletContext(); XMLConfiguration config = new XMLConfiguration("cfg.xml"); config.setReloadingStrategy(new FileChangedReloadingStrategy()); this.context.setAttribute("mycfg", config); } catch (Exception e) { e.printStackTrace(); } } @Override public void contextDestroyed(ServletContextEvent arg0) { this.context = null; } } web.xml <listener> <listener-class>mypackage.MyAppCfg</listener-class> </listener> and later acces them in the webapp via this.cfg = (XMLConfiguration) servletRequest.getAttribute("mycfg");

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• Dynamically set generic type argument

  - by fearofawhackplanet

  Following on from my question here, I'm trying to create a generic value equality comparer. I've never played with reflection before so not sure if I'm on the right track, but anyway I've got this idea so far: bool ContainSameValues<T>(T t1, T t2) { if (t1 is ValueType || t1 is string) { return t1.Equals(t2); } else { IEnumerable<PropertyInfo> properties = t1.GetType().GetProperties().Where(p => p.CanRead); foreach (var property in properties) { var p1 = property.GetValue(t1, null); var p2 = property.GetValue(t2, null); if( !ContainSameValues<p1.GetType()>(p1, p2) ) return false; } } return true; } This doesn't compile because I can't work out how to set the type of T in the recursive call. Is it possible to do this dynamically at all? There are a couple of related questions on here which I have read but I couldn't follow them enough to work out how they might apply in my situation.

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• Uploading file to DropBox causing UnlinkedException

  - by Boardy

  I am currently working on android project and trying to enable DropBox functionality. I've selected the access type to App Only, and I can successfully authenticate and it creates an Apps directory and inside that creates a directory with the name of my app. When I then try to put a file in the DropBox directory it goes into the DropBoxException catch and in the logcat prints com.dropbox.client2.exception.DropboxUnlinkedException. I've done a google and from what I've seen this happens if the apps directory has been deleted and so authentication is required to be re-done, but this isn't the case, I have deleted it and I am putting the file straight after doing the authentication. Below is the code that retrieves the keys and stores the file on dropbox. AccessTokenPair tokens = getTokens(); UploadFile uploadFile = new UploadFile(context, common, this, mDBApi); uploadFile.execute(mDBApi); Below is the code for the getTokens method (don't think this would help but you never know) private AccessTokenPair getTokens() { AccessTokenPair tokens; SharedPreferences prefs = context.getSharedPreferences("prefs", 0); String key = prefs.getString("dropbox_key", ""); String secret = prefs.getString("dropbox_secret", ""); tokens = new AccessTokenPair(key, secret); return tokens; } Below is the class that extends the AsyncTask to perform the upload class UploadFile extends AsyncTask<DropboxAPI<AndroidAuthSession>, Void, bool> { Context context; Common common; Synchronisation sync; DropboxAPI<AndroidAuthSession> mDBApi; public UploadFile(Context context, Common common, Synchronisation sync, DropboxAPI<AndroidAuthSession> mDBApi) { this.context = context; this.common = common; this.sync = sync; this.mDBApi = mDBApi; } @Override protected bool doInBackground(DropboxAPI<AndroidAuthSession>... params) { try { File file = new File(Environment.getExternalStorageDirectory() + "/BoardiesPasswordManager/dropbox_sync.xml"); FileInputStream inputStream = new FileInputStream(file); Entry newEntry = mDBApi.putFile("android_sync.xml", inputStream, file.length(), null, null); common.showToastMessage("Successfully uploade Rev: " + newEntry.rev, Toast.LENGTH_LONG); } catch (IOException ex) { Log.e("DropBoxError", ex.toString()); } catch (DropboxException e) { Log.e("DropBoxError", e.toString()); e.printStackTrace(); } return null; } I have no idea why it would display the UnlinkedException so any help would be greatly appreciated.

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• Query joining in sql server 2005

  - by Domnic

  I have two queries like: SELECT PC_COMP_CODE, PC_SL_LDGR_CODE, PC_SL_ACNO ACCOUNT, COUNT(PC_CHEQUE_NO) CHQS, SUM(CONVERT(FLOAT, PC_AMOUNT)) CHQ_AMT FROM GLAS_PDC_CHEQUES WHERE PC_COMP_CODE = '1' AND PC_DISCD IS NULL GROUP BY PC_SL_LDGR_CODE, PC_SL_ACNO ,PC_COMP_CODE ORDER BY PC_SL_ACNO -------------------------------------------------- SELECT COAD_PTY_FULL_NAME,PC_COMP_CODE, PC_SL_LDGR_CODE, PC_SL_ACNO, PC_DEPT_NO, PC_DOC_TYPE, PC_CHEQUE_NO, PC_BANK_AC_NO FROM GLAS_PTY_ADDRESS,GLAS_SBLGR_MASTERS,GLAS_PDC_CHEQUES WHERE COAD_COMP_CODE = '1' AND SLMA_COMP_CODE = COAD_COMP_CODE AND SLMA_ADDR_ID = COAD_ADDR_ID AND SLMA_LDGRCTL_CODE = PC_SL_LDGR_CODE AND PC_COMP_CODE=SLMA_COMP_CODE AND SLMA_ACNO = PC_SL_ACNO AND SLMA_LDGRCTL_YEAR = DBO.GLAS_VALIDATIONS_GET_OPEN_YEAR(PC_COMP_CODE) If I execute first query alone I get 5 records... If I join the above two query like: SELECT PC_COMP_CODE, PC_SL_LDGR_CODE, PC_SL_ACNO ACCOUNT, COUNT(PC_CHEQUE_NO) CHQS, SUM(CONVERT(FLOAT, PC_AMOUNT)) CHQ_AMT, COAD_PTY_FULL_NAME FROM GLAS_PDC_CHEQUES LEFT OUTER JOIN GLAS_SBLGR_MASTERS ON( SLMA_COMP_CODE=PC_COMP_CODE AND SLMA_LDGRCTL_CODE = PC_SL_LDGR_CODE AND SLMA_ACNO = PC_SL_ACNO ) LEFT OUTER JOIN GLAS_PTY_ADDRESS ON( SLMA_COMP_CODE = COAD_COMP_CODE AND SLMA_ADDR_ID = COAD_ADDR_ID) WHERE PC_COMP_CODE = '1' AND PC_DISCD IS NULL AND SLMA_LDGRCTL_YEAR = DBO.GLAS_VALIDATIONS_GET_OPEN_YEAR(PC_COMP_CODE) GROUP BY PC_SL_LDGR_CODE, PC_SL_ACNO ,PC_COMP_CODE,COAD_PTY_FULL_NAME ORDER BY PC_SL_ACNO then I just get 2 records.... I need that 5 records to display after join..... How can I do it?

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• Using "prevent execution of method" flags

  - by tpaksu

  First of all I want to point out my concern with some pseudocode (I think you'll understand better) Assume you have a global debug flag, or class variable named "debug", class a : var debug = FALSE and you use it to enable debug methods. There are two types of usage it as I know: first in a method : method a : if debug then call method b; method b : second in the method itself: method a : call method b; method b : if not debug exit And I want to know, is there any File IO or stack pointer wise difference between these two approaches. Which usage is better, safer and why?

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• Twitter Authentication through Android's AccountManager classes.

  - by Robby Pond

  I am working on a twitter based app and am trying to incorporate Android's built-in Account support for Twitter. The following code works to popup the confirmation dialog for my app to access twitter but I am unsure of what to pass in as the authenticationType. Any help would be appreciated. I've googled all over the place and can't seem to find the correct answer. It goes in place of "oauth" below. AccountManager am = AccountManager.get(this); Account[] accts = am.getAccountsByType(TWITTER_ACCOUNT_TYPE); if(accts.length > 0) { Account acct = accts[0]; am.getAuthToken(acct, "oauth"/*what goes here*/, null, this, new AccountManagerCallback<Bundle>() { @Override public void run(AccountManagerFuture<Bundle> arg0) { try { Bundle b = arg0.getResult(); Log.e("TrendDroid", "THIS AUTHTOKEN: " + b.getString(AccountManager.KEY_AUTHTOKEN)); } catch (Exception e) { Log.e("TrendDroid", "EXCEPTION@AUTHTOKEN"); } }}, null); }

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• what does this code do?

  - by bstullkid

  It looks like this just sends a ping, but whats the point of that when you can just use ping? int main (int argc, char *argv[]) { unsigned int pid = 0; char buffer[2]; char *args[] = { "/bin/ping", "-c", "5", NULL, NULL }; if (argc != 2) return 0; args[3] = strdup(argv[1]); for (;;) { gets(buffer); /* FTW */ if (buffer[0] == 0x6e) break; switch (pid = fork()) { case -1: printf("Error Forking\n"); exit(255); case 0: execvp(args[0], args); exit(1); default: break; } } return 255; }

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• How to handle Application_BeginRequest using a custom filter in asp.net mvc?

  - by denis_n

  How to handle Application_BeginRequest using a custom filter in asp.net mvc? I want to restore session only for one route (~/my-url). I would be cool, if I could create a custom filter and handle that. protected void Application_BeginRequest(object sender, EventArgs e) { var context = HttpContext.Current; if (string.Equals("~/my-url", context.Request.AppRelativeCurrentExecutionFilePath, StringComparison.OrdinalIgnoreCase)) { string sessionId = context.Request.Form["sessionId"]; if (sessionId != null) { HttpCookie cookie = context.Request.Cookies.Get("ASP.NET_SessionId"); if (cookie == null) { cookie = new HttpCookie("ASP.NET_SessionId"); } cookie.Value = sessionId; context.Request.Cookies.Set(cookie); } }

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• How do I find the top N batters per year?

  - by Drew Stephens

  I'm playing around with the Lahman Baseball Database in a MySQL instance. I want to find the players who topped home runs (HR) for each year. The Batting table has the following (relevant parts) of its schema: +-----------+----------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+----------------------+------+-----+---------+-------+ | playerID | varchar(9) | NO | PRI | | | | yearID | smallint(4) unsigned | NO | PRI | 0 | | | HR | smallint(3) unsigned | YES | | NULL | | +-----------+----------------------+------+-----+---------+-------+ For each year, every player has an entry (between hundreds and 12k per year, going back to 1871). Getting the top N hitters for a single year is easy: SELECT playerID,yearID,HR FROM Batting WHERE yearID=2009 ORDER BY HR DESC LIMIT 3; +-----------+--------+------+ | playerID | yearID | HR | +-----------+--------+------+ | pujolal01 | 2009 | 47 | | fieldpr01 | 2009 | 46 | | howarry01 | 2009 | 45 | +-----------+--------+------+ But I'm interested in finding the top 3 from every year. I've found solutions like this, describing how to select the top from a category and I've tried to apply it to my problem, only to end up with a query that never returns: SELECT b.yearID, b.playerID, b.HR FROM Batting AS b LEFT JOIN Batting b2 ON (b.yearID=b2.yearID AND b.HR <= b2.HR) GROUP BY b.yearID HAVING COUNT(*) <= 3; Where have I gone wrong?

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• Game maps with "counties" that are split along lines that aren't necessarily straight

  - by pm_2

  I want to create a game environment that supports a 2D map. This is a really basic map, but must be split along lines that are not necessarily straight. So imagine a country with county boundaries. I then want to be able to detect drag / drop events within these counties. What I'm really looking for here is a pointer to where to start on this (how it has been done before - any existing libraries out there), as I'm sure that what I'm trying to do is not new - although I can't find a beginners guide for this anywhere.

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• Debugging stack data not assigned to a named variable

  - by gibbss

  Is there a way to view stack elements like un-assigned return values or exceptions that not assigned to a local variable? (e.g. throw new ...) For example, suppose I have code along the lines of: public String foo(InputStream in) throws IOException { NastyObj obj = null; try { obj = new NastyObj(in); return (obj.read()); } finally { if (obj != null) obj.close(); } } Is there any way to view the return or exception value without stepping to a higher level frame where it is assigned? This is particularly relevant with exceptions because you often have to step back up through a number of frames to find an actual handler. I usually use the Eclipse debugging environment, but any answer is appreciated. Also, if this cannot be done, can you explain why? (JVM, JPDA limitation?)

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• Programming style: should you return early if a guard condition is not satisfied?

  - by John Topley

  One thing I've sometimes wondered is which is the better style out of the two shown below (if any)? Is it better to return immediately if a guard condition hasn't been satisfied, or should you only do the other stuff if the guard condition is satisfied? For the sake of argument, please assume that the guard condition is a simple test that returns a boolean, such as checking to see if an element is in a collection, rather than something that might affect the control flow by throwing an exception. // Style 1 public SomeType aMethod() { SomeType result = null; if (!guardCondition()) { return result; } doStuffToResult(result); doMoreStuffToResult(result); return result; } // Style 2 public SomeType aMethod() { SomeType result = null; if (guardCondition()) { doStuffToResult(result); doMoreStuffToResult(result); } return result; }

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• difference fixed width strings and zero-terminated strings

  - by robUK

  Hello, gcc 4.4.4 c89 I got into a recent discussion about "fixed width strings" and "zero terminated strings". When I think about this. They seem to be the same thing. A string with a terminating null. i.e. char *name = "Joe bloggs"; Is a fixed width string that cannot be changed. And also has a terminating null. Also in the discussion I was told that strncpy should never been used on 'zero terminated strings'. Many thanks for any susgestions,

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• Why JPA injection not works on @PersistentUnit

  - by Dewfy

  Hello colleagues! It is continues of question ( http://stackoverflow.com/questions/2570976/struts-2-bean-is-not-created ) I'm using struts2 + toplink in my very simple web application under Tomcat. On the page I would like use iteration tag. That is why I've declared some factory (SomeFactory) that resolves collection of entities (Entity). Per article: http://download-uk.oracle.com/docs/cd/B32110_01/web.1013/b28221/usclient005.htm#CIHCEHHG the only thing I need is declaration: @PersistenceContext(unitName="name_in_persistence_xml") public class SomeFactory { @PersistenceUnit(unitName="name_in_persistence_xml") EntityManagerFactory emf; public EntityManager getEntityManager() { assert(emf != null); //HERE every time it is null return emf.createEntityManager(); } public Collection<Entity> getAll() { return getEntityManager().createNamedQuery("Entity.findAll").getResultList(); } } What is wrong? May be i miss something in web.xml? How to pre-init toplink for web application to allow injection happen?

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• How to listen for file system changes MAC - kFSEventStreamCreateFlagWatchRoot

  - by Cocoa Newbie

  Hi All, I am listening for Directory and disk changes in a COCOA project using FSEvents. I need to get events when a root folder is renamed or deleted. So, I passed kFSEventStreamCreateFlagWatchRoot while creating the FSEventStream.But even if I delete or rename the root folder I am not getting corresponding FSEventStreamEventFlags. Any idea what could possibly be the issue. I am listening for changes in a USB mounted device. I used both FSEventStreamCreate and FSEventStreamCreateRelativeToDevice. One thing I notices is when I try with FSEventStreamCreate I get the following error message while creating FSEventStream: (CarbonCore.framework) FSEventStreamCreate: watch_all_parents: error trying to add kqueue for fd 7 (/Volumes/NO NAME; Operation not supported) But with FSEventStreamCreateRelativeToDevice there are no errors but still not getting kFSEventStreamEventFlagRootChanged in event flags. Also, while creation using FSEventStreamCreateRelativeToDevice apple say's if I want to listen to root path changes pass emty string "". But I am not able to listen to root path changes by passing empty string. But when I pass "/" it works. But even for "/" I do not get any proper FSEventStreamEventFlags. I am pasting the code here: -(void) subscribeFileSystemChanges:(NSString*) path { PRINT_FUNCTION_BEGIN; // if already subscribed then unsubscribe if (stream) { FSEventStreamStop(stream); FSEventStreamInvalidate(stream); /* will remove from runloop */ FSEventStreamRelease(stream); } FSEventStreamContext cntxt = {0}; cntxt.info = self; CFArrayRef pathsToWatch = CFArrayCreate(NULL, (const void**)&path, 1, NULL); stream = FSEventStreamCreate(NULL, &feCallback, &cntxt, pathsToWatch, kFSEventStreamEventIdSinceNow, 1, kFSEventStreamCreateFlagWatchRoot ); FSEventStreamScheduleWithRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode); FSEventStreamStart(stream); } call back function: static void feCallback(ConstFSEventStreamRef streamRef, void* pClientCallBackInfo, size_t numEvents, void* pEventPaths, const FSEventStreamEventFlags eventFlags[], const FSEventStreamEventId eventIds[]) {? char** ppPaths = (char**)pEventPaths; int i; for (i = 0; i < numEvents; i++) { NSLog(@"Event Flags %lu Event Id %llu", eventFlags[i], eventIds[i]); NSLog(@"Path changed: %@", [NSString stringWithUTF8String:ppPaths[i]]); } } Thanks a lot in advance.

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• sql Code For searching

  - by Manoj Wadhwani

  Could any body send code for searching from talbe which has multiple parameter and parameter can contain value or can be null.

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• SQL GROUP BY with "default values"

  - by Christoph Schiessl

  I'm trying to create SELECT statement with a GROUP BY clause, which should return "default values". Imagine the following simple MySQL table: CREATE TABLE `tracker` ( `id` INTEGER PRIMARY KEY auto_increment, `date` DATETIME NOT NULL, `customer_id` INTEGER NOT NULL ); The table contains only one record: INSERT INTO `tracker` (`date`, `customer_id`) VALUES('2010-05-03', 1); After wards I'm executing the following SQL query: SELECT DATE(`date`), COUNT(customer_id) FROM tracker WHERE DATE(`date`) >= '2010-05-01' AND DATE(`date`) <= '2010-05-05' GROUP BY DATE(`date`) ORDER BY DATE(`date`); And get the expected result set: +----+---------------------+-------------+ | id | date | customer_id | +----+---------------------+-------------+ | 1 | 2010-05-10 00:00:00 | 1 | +----+---------------------+-------------+ However, I would like the result set to look like this: +--------------+--------------------+ | DATE(`date`) | COUNT(customer_id) | +--------------+--------------------+ | 2010-05-01 | 0 | | 2010-05-02 | 0 | | 2010-05-03 | 1 | | 2010-05-04 | 0 | | 2010-05-05 | 0 | +--------------+--------------------+ Is it possible to achieve this behavior?

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• What is wrong with the program

  - by Naveen

  I am getting error for below code: #include "parent_child.h" #include "child_proces.h" int main() { childprocess::childprocess(){} childprocess::~childprocess(){} /* parentchild *cp = NULL; act.sa_sigaction = cp->SignalHandlerCallback; act.sa_flags = SA_SIGINFO; sigaction(SIGKILL, &act, NULL); }*/ printf("Child process\n"); return 0; } ERROR: child_proces.cpp: In function âint main()â: child_proces.cpp:11: error: expected ;' before â{â token child_proces.cpp:12: error: no matching function for call to âchildprocess::~childprocess()â child_proces.h:9: note: candidates are: childprocess::~childprocess() child_proces.cpp:12: error: expected;' before â{â token

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• empty() not a valid callback?

  - by user151841

  I'm trying to use empty() in array mapping in php. I'm getting errors that it's not a valid callback. $ cat test.php <? $arrays = array( 'arrEmpty' => array( '','','' ), ); foreach ( $arrays as $key => $array ) { echo $key . "\n"; echo array_reduce( $array, "empty" ); var_dump( array_map("empty", $array) ); echo "\n\n"; } $ php test.php arrEmpty Warning: array_reduce(): The second argument, 'empty', should be a valid callback in /var/www/authentication_class/test.php on line 12 Warning: array_map(): The first argument, 'empty', should be either NULL or a valid callback in /var/www/authentication_class/test.php on line 13 NULL Shouldn't this work? Long story: I'm trying to be (too?) clever and checking that all array values are not empty strings.

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• Elapsed time of running a C program

  - by yCalleecharan

  Hi, I would like to know what lines of C code to add to a program so that it tells me the total time that the program takes to run. I guess there should be counter initialization near the beginning of main and one after the main function ends. Is the right header clock.h? Thanks a lot... Update I have a Win Xp machine. Is it just adding clock() at the beginning and another clock() at the end of the program? Then I can estimate the time difference. Yes, you're right it's time.h. Here's my code: #include <stdio.h> #include <stdlib.h> #include <math.h> #include <share.h> #include <time.h> void f(long double fb[], long double fA, long double fB); int main() { clock_t start, end; start = clock(); const int ARRAY_SIZE = 11; long double* z = (long double*) malloc(sizeof (long double) * ARRAY_SIZE); int i; long double A, B; if (z == NULL) { printf("Out of memory\n"); exit(-1); } A = 0.5; B = 2; for (i = 0; i < ARRAY_SIZE; i++) { z[i] = 0; } z[1] = 5; f(z, A, B); for (i = 0; i < ARRAY_SIZE; i++) printf("z is %.16Le\n", z[i]); free(z); z = NULL; end = clock(); printf("Took %ld ticks\n", end-start); printf("Took %f seconds\n", (double)(end-start)/CLOCKS_PER_SEC); return 0; } void f(long double fb[], long double fA, long double fB) { fb[0] = fb[1]* fA; fb[1] = fb[1] - 1; return; } Some errors with MVS2008: testim.c(16) : error C2143: syntax error : missing ';' before 'const' testim.c(18) :error C2143: syntax error : missing ';' before 'type' testim.c(20) :error C2143: syntax error : missing ';' before 'type' testim.c(21) :error C2143: syntax error : missing ';' before 'type' testim.c(23) :error C2065: 'z' : undeclared identifier testim.c(23) :warning C4047: '==' : 'int' differs in levels of indirection from 'void *' testim.c(28) : error C2065: 'A' : undeclared identifier testim.c(28) : warning C4244: '=' : conversion from 'double' to 'int', possible loss of data and it goes to 28 errors. Note that I don't have any errors/warnings without your clock codes. LATEST NEWS: I unfortunately didn't get a good reply here. But after a search on Google, the code is working. Here it is: #include <stdio.h> #include <stdlib.h> #include <math.h> #include <share.h> #include <time.h> void f(long double fb[], long double fA, long double fB); int main() { clock_t start = clock(); const int ARRAY_SIZE = 11; long double* z = (long double*) malloc(sizeof (long double) * ARRAY_SIZE); int i; long double A, B; if (z == NULL) { printf("Out of memory\n"); exit(-1); } A = 0.5; B = 2; for (i = 0; i < ARRAY_SIZE; i++) { z[i] = 0; } z[1] = 5; f(z, A, B); for (i = 0; i < ARRAY_SIZE; i++) printf("z is %.16Le\n", z[i]); free(z); z = NULL; printf("Took %f seconds\n", ((double)clock()-start)/CLOCKS_PER_SEC); return 0; } void f(long double fb[], long double fA, long double fB) { fb[0] = fb[1]* fA; fb[1] = fb[1] - 1; return; } Cheers

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