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• How to code for Alternate Course AKA Rainy Day Scenary?

  - by janetsmith

  Alternate course is something when user doesn't do what you expected, e.g. key in wrong password, pressing back button, or database error. For any programming project, alternate course accounts for more than 50% of a project timeline. It is important. However, most computer books only focus on Basic Course (when everything goes fine). Basic course is rather simple, compared to Alternate course, because this is normally given by client. Alternate course is what we, as a programmer or Business Analyst needs to take care of. Java has some built-in mechanism (try-catch) to force us to handle those unexpected behavior. The question is, how to handle them? Any pattern to follow? Any guideline or industry practice for handling alternate course?

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• Https in java ends up with strange results

  - by Senne

  I'm trying to illustrate to students how https is used in java. But i have the feeling my example is not really the best out there... The code works well on my windows 7: I start the server, go to https://localhost:8080/somefile.txt and i get asked to trust the certificate, and all goes well. When I try over http (before or after accepting the certificate) I just get a blank page, which is ok for me. BUT when I try the exact same thing on my windows XP: Same thing, all goes well. But then (after accepting the certificate first), I'm also able to get all the the files through http! (if I first try http before https followed by accepting the certificate, I get no answer..) I tried refreshing, hard refreshing a million times but this should not be working, right? Is there something wrong in my code? I'm not sure if I use the right approach to implement https here... package Security; import java.io.*; import java.net.*; import java.util.*; import java.util.concurrent.Executors; import java.security.*; import javax.net.ssl.*; import com.sun.net.httpserver.*; public class HTTPSServer { public static void main(String[] args) throws IOException { InetSocketAddress addr = new InetSocketAddress(8080); HttpsServer server = HttpsServer.create(addr, 0); try { System.out.println("\nInitializing context ...\n"); KeyStore ks = KeyStore.getInstance("JKS"); char[] password = "vwpolo".toCharArray(); ks.load(new FileInputStream("myKeys"), password); KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509"); kmf.init(ks, password); SSLContext sslContext = SSLContext.getInstance("TLS"); sslContext.init(kmf.getKeyManagers(), null, null); // a HTTPS server must have a configurator for the SSL connections. server.setHttpsConfigurator (new HttpsConfigurator(sslContext) { // override configure to change default configuration. public void configure (HttpsParameters params) { try { // get SSL context for this configurator SSLContext c = getSSLContext(); // get the default settings for this SSL context SSLParameters sslparams = c.getDefaultSSLParameters(); // set parameters for the HTTPS connection. params.setNeedClientAuth(true); params.setSSLParameters(sslparams); System.out.println("SSL context created ...\n"); } catch(Exception e2) { System.out.println("Invalid parameter ...\n"); e2.printStackTrace(); } } }); } catch(Exception e1) { e1.printStackTrace(); } server.createContext("/", new MyHandler1()); server.setExecutor(Executors.newCachedThreadPool()); server.start(); System.out.println("Server is listening on port 8080 ...\n"); } } class MyHandler implements HttpHandler { public void handle(HttpExchange exchange) throws IOException { String requestMethod = exchange.getRequestMethod(); if (requestMethod.equalsIgnoreCase("GET")) { Headers responseHeaders = exchange.getResponseHeaders(); responseHeaders.set("Content-Type", "text/plain"); exchange.sendResponseHeaders(200, 0); OutputStream responseBody = exchange.getResponseBody(); String response = "HTTP headers included in your request:\n\n"; responseBody.write(response.getBytes()); Headers requestHeaders = exchange.getRequestHeaders(); Set<String> keySet = requestHeaders.keySet(); Iterator<String> iter = keySet.iterator(); while (iter.hasNext()) { String key = iter.next(); List values = requestHeaders.get(key); response = key + " = " + values.toString() + "\n"; responseBody.write(response.getBytes()); System.out.print(response); } response = "\nHTTP request body: "; responseBody.write(response.getBytes()); InputStream requestBody = exchange.getRequestBody(); byte[] buffer = new byte[256]; if(requestBody.read(buffer) > 0) { responseBody.write(buffer); } else { responseBody.write("empty.".getBytes()); } URI requestURI = exchange.getRequestURI(); String file = requestURI.getPath().substring(1); response = "\n\nFile requested = " + file + "\n\n"; responseBody.write(response.getBytes()); responseBody.flush(); System.out.print(response); Scanner source = new Scanner(new File(file)); String text; while (source.hasNext()) { text = source.nextLine() + "\n"; responseBody.write(text.getBytes()); } source.close(); responseBody.close(); exchange.close(); } } }

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• TcpListener Socket still active after program exits.

  - by lnical

  I'm trying to stop a TCP Listener as my program is exiting. I do not care about any data that is currently active on the socket or any of the active client sockets. The socket clean up code is essentially: try { myServer.Server.Shutdown(SocketShutdown.Both) } catch (Exception ex) { LogException(ex) } myServer.Server.Close(0) myServer.Stop() myServer is a TCPListener On some occasions, Shutdown will thrown an exception System.Net.Sockets.SocketException: A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied at System.Net.Sockets.Socket.Shutdown(SocketShutdown how) When this happens, the socket is never released. Even after the application exits netstat shows the socket is still in the listening state. I have not been able to create definitive reproduction scenerio, it happens at seemingly random times. Client Sockets are cleaned up independently. Do you have any suggestions to help me make this socket die?

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• How to retrieve XML attribute for custom control

  - by David

  I've created a combo box control with a edittext and spinner. I'm trying to let the android:prompt attribute be passed onto the spinner, which means I need to catch it in the constructor which passes my the AttributeSet and set it on the spinner. I can't figure out how to get the value of the prompt. I'm trying, int[] ra = { android.R.attr.prompt }; TypedArray ta = context.getTheme().obtainStyledAttributes(ra); int id = ta.getResourceId(0, 0); I get back 0, which means it didn't find the attribute. I also did a ta.count() which returned 0. So I'm not getting anything back. My XML simply defines an android:prompt value. Thanks

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• VB.NET For Each steps into loop body for an IEnumerable collection! How? Why?

  - by Paul Sasik

  This is weird. I have a class that inherits from IEnumrable whose Count property is reporting 0 (zero) elements but the For Each loop steps into the loop body and tries to use the variable where it should just be moving on. My code: On Error Resume Next Dim d As Foo For Each d In fooCollection ' use d and throws an exception Next d Weirder still, every time d is accessed i get an exception thrown in the output window: A first chance exception of type 'System.NullReferenceException' but i'm not stopping on the exception (not in a try/catch block). Is "On Error Resume Next" causing this weirdness? Weirdness found: Per Rowland's and JohnH's comments i checked the Foo class: The GetEnumerator method inside of Foo didn't actually return anything! It had an empty body. That coupled with the On Error Resume Next before the loop caused the havoc! Wow this was ugly. Thanks for the clues guys!

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• How to handle failure to release a resource which is contained in a smart pointer?

  - by cj

  How should an error during resource deallocation be handled, when the object representing the resource is contained in a shared pointer? Smart pointers are a useful tool to manage resources safely. Examples of such resources are memory, disk files, database connections, or network connections. // open a connection to the local HTTP port boost::shared_ptr<Socket> socket = Socket::connect("localhost:80"); In a typical scenario, the class encapsulating the resource should be noncopyable and polymorphic. A good way to support this is to provide a factory method returning a shared pointer, and declare all constructors non-public. The shared pointers can now be copied from and assigned to freely. The object is automatically destroyed when no reference to it remains, and the destructor then releases the resource. /** A TCP/IP connection. */ class Socket { public: static boost::shared_ptr<Socket> connect(const std::string& address); virtual ~Socket(); protected: Socket(const std::string& address); private: // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; But there is a problem with this approach. The destructor must not throw, so a failure to release the resource will remain undetected. A common way out of this problem is to add a public method to release the resource. class Socket { public: virtual void close(); // may throw // ... }; Unfortunately, this approach introduces another problem: Our objects may now contain resources which have already been released. This complicates the implementation of the resource class. Even worse, it makes it possible for clients of the class to use it incorrectly. The following example may seem far-fetched, but it is a common pitfall in multi-threaded code. socket->close(); // ... size_t nread = socket->read(&buffer[0], buffer.size()); // wrong use! Either we ensure that the resource is not released before the object is destroyed, thereby losing any way to deal with a failed resource deallocation. Or we provide a way to release the resource explicitly during the object's lifetime, thereby making it possible to use the resource class incorrectly. There is a way out of this dilemma. But the solution involves using a modified shared pointer class. These modifications are likely to be controversial. Typical shared pointer implementations, such as boost::shared_ptr, require that no exception be thrown when their object's destructor is called. Generally, no destructor should ever throw, so this is a reasonable requirement. These implementations also allow a custom deleter function to be specified, which is called in lieu of the destructor when no reference to the object remains. The no-throw requirement is extended to this custom deleter function. The rationale for this requirement is clear: The shared pointer's destructor must not throw. If the deleter function does not throw, nor will the shared pointer's destructor. However, the same holds for other member functions of the shared pointer which lead to resource deallocation, e.g. reset(): If resource deallocation fails, no exception can be thrown. The solution proposed here is to allow custom deleter functions to throw. This means that the modified shared pointer's destructor must catch exceptions thrown by the deleter function. On the other hand, member functions other than the destructor, e.g. reset(), shall not catch exceptions of the deleter function (and their implementation becomes somewhat more complicated). Here is the original example, using a throwing deleter function: /** A TCP/IP connection. */ class Socket { public: static SharedPtr<Socket> connect(const std::string& address); protected: Socket(const std::string& address); virtual Socket() { } private: struct Deleter; // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; struct Socket::Deleter { void operator()(Socket* socket) { // Close the connection. If an error occurs, delete the socket // and throw an exception. delete socket; } }; SharedPtr<Socket> Socket::connect(const std::string& address) { return SharedPtr<Socket>(new Socket(address), Deleter()); } We can now use reset() to free the resource explicitly. If there is still a reference to the resource in another thread or another part of the program, calling reset() will only decrement the reference count. If this is the last reference to the resource, the resource is released. If resource deallocation fails, an exception is thrown. SharedPtr<Socket> socket = Socket::connect("localhost:80"); // ... socket.reset();

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• multiple FileSystemWatchers to monitor files on local system?

  - by Jason Crowes

  We're writing a text editor like tool for our internal accounting package system that has actions that can be done by our own Xml language specs. These macro commands are specified in Xml files and we need the ability to monitor if files openned have bean modified externally. The only problem is that there maybe 20-30 files with different paths openned at any one time. Would it be good to use multiple FileSystemWatchers for this scenario? Or would it be better to monitor the root drive and catch specific events that match an open file in the editor (though lots of events could be raised). Some are local drives (C,D,E) others are their network drives (U,X,G,H). Files are quite chunky too about 300-400Kb.

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• Using JSF, JPA and DAO. Without Spring?

  - by ich-bin-drin

  Hi, till now i still worked with JSF and JPA without DAOs. Now i'd like to use DAOs. But how can i initialize the EntityManager in the DAO-Classes? public class AdresseHome { @PersistenceContext private EntityManager entityManager; public void persist(Adresse transientInstance) { log.debug("persisting Adresse instance"); try { entityManager.persist(transientInstance); log.debug("persist successful"); } catch (RuntimeException re) { log.error("persist failed", re); throw re; } } } Have I to use Spring or is there a solution that works without Spring? Thanks.

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• Binding Navigation Property with Entity Framework

  - by JSmaga

  Hi, I have another question about binding using C# and the entity framework. Here, I'm looking to bind a navigation property to a listbox or a listview. I saw on different posts that if I update the collection using code behind the list would not be notified because the collection does not handle notification (it's always the same problem anyway). People suggested to use an ObservableCollection for example, but, and here is my question, this comes down to basically duplicate the collection and hence, if I modify it, I'd have to handle in code-behind the fact that the change has also to be applied to the "original" navigation property right? If that's the case, I was thinking: why not create a custom property called, say, MyObservableNavigationProperty in a partial class. I could then interact only with this collection, catch the event when the collection is changed and apply the change to the "original" collection. Is that a nice way to do the trick? or am I getting all confused here....

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• Timeout LinqToSql inserting millions of records

  - by Bas

  I'm inserting approximently 3 million records in a database using this solution. Eventually when the application has been inserting records for a while (my last run lasted around 4 hours), it gives a timeout with the following SqlException: "SqlExcepetion: Timeout expired. The timeoutperiod elapsed prior to completion of the operation or the server is not responding." What's the best way to handle this exception? Is there a way to prevent this from happening or should I catch the exception? Thanks in advance!

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• Visual Studio 2008 Macro for Building does not block thread

  - by Climber104

  Hello, I am trying to write a macro for Building my application, kicking off an external tool, and ataching the debugger to that external tool. Everything is working except for the building. It builds, but it is not blocking the thread so the external tool gets kicked off before it can finish. Is there a way I can run ExecuteCommand and wait for the thread to finish? Code is below: DTE.ExecuteCommand("ClassViewContextMenus.ClassViewProject.Build") DTE.ExecuteCommand("Tools.ExternalCommand11") Try Dim dbg2 As EnvDTE80.Debugger2 = DTE.Debugger Dim trans As EnvDTE80.Transport = dbg2.Transports.Item("Default") Dim dbgeng(1) As EnvDTE80.Engine dbgeng(0) = trans.Engines.Item("Managed") Dim proc2 As EnvDTE80.Process2 = dbg2.GetProcesses(trans, "MINIPC").Item("_nStep.exe") proc2.Attach2(dbgeng) Catch ex As System.Exception MsgBox(ex.Message) End Try

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• Google App Engine PersistenceManager can process multiple objects ?

  - by Frank

  I have some code like this : PersistenceManager pm=PMF.get().getPersistenceManager(); String query="select from "+PayPal_Message.class.getName()+" where processed == false order by time desc"; List<PayPal_Message> messages=(List<PayPal_Message>)pm.newQuery(query).execute(); if (messages.isEmpty()) { } else { for (PayPal_Message g : messages) { Contact_Info_Entry A_Contact_Entry=Process_PayPal_Message_To_Get_A_License(g.getContent().getValue()); pm=PMF.get().getPersistenceManager(); try { pm.makePersistent(A_Contact_Entry); g.setProcessed(true); pm.makePersistent(g); } catch (Exception e) { Send_Email(Email_From,"[email protected]","Servlet Error Message [ "+time+" ]",new Text(e.toString())); } // finally { pm.close(); } } } pm.close(); I wonder if it's ok to use the pm above to process multiple objects before closing it. Or do I have to get and close pm for processing each object ?

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• Saving part of audio file (java)

  - by m159701m

  Hi evryone, While playing an audio file (.wav) I want , if I resort to ctrl+c , to stop the playback and save part of the audio file in a file called "file2.wav". Here's the thread I'd like to add to my code. Unfortunately it doesn't work at all. Thanks in advance class myThread extends Thread{ public void run(){ try { PipedOutputStream poStream = new PipedOutputStream(); PipedInputStream piStream = new PipedInputStream(); poStream.connect(piStream); File cutaudioFile = new File ("file2.wav"); AudioInputStream ais = new AudioInputStream(piStream, AudioFileFormat.Type.WAVE , cutaudioFile); poStream.write(ais,AudioFileFormat.Type.WAVE,cutaudioFile); }catch (Exception e){ e.printStackTrace(); } } // end run } // end myThread

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• Controlling CodeModel's code output formatting: putting lines between namespace declarations

  - by devoured elysium

  I'm making some experiments with Visual Studio's CodeModel. I tried creating a file with two namespaces in there through VS's Code Model: CodeModel codeModel = projItem.ContainingProject.CodeModel; codeModel.AddNamespace("Namespaces.FirstNamespace", "namespacestest.cs"); codeModel.AddNamespace("Namespaces.SecondNamespace", "namespacestest.cs"); the output of such code is: //file namespacestest.cs namespace Namespaces.FirstNamespace { } namespace Namespaces.SecondNamespace { } Which is almost what I'm looking for. The only catch here is that I'd like to control the spacing: having at least one line between the first and the second namespace. Does by chance anyone know of a way of achieving this? This is what I want: //file namespacestest.cs namespace Namespaces.FirstNamespace { } namespace Namespaces.SecondNamespace { } Thanks

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• WxWidgets custom events

  - by Klaus

  Hello, I'm trying to use a custom event in my WxWidgets C++ application, like described here. In the constructor of my wxApp: Connect(wxID_ANY, wxCommandEventHandler(APP::OnMyEvent)); Then the function that should catch the event: void APP::OnMyEvent(wxCommandEvent& event) { exit(0); //testing } Finally, to test it: wxCommandEvent MyEvent(wxEVT_COMMAND_BUTTON_CLICKED); wxPostEvent(this, MyEvent); I launch the thing...but it seems that the event is not posted or not caught. Does someone understand this behaviour ?

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• Element point map for html5 canvas element, need algorithm

  - by Artiom Chilaru

  I'm currently working on a pure html 5 canvas implementation of the "flying tag cloud sphere", which many of you have undoubtedly seen as a flash object in some pages. The tags are drawn fine, and the performance is satisfactory, but there's one thing in the canvas element that's kind of breaking this idea: you can't identify the objects that you've drawn on a canvas, as it's just a simple flat "image".. What I have to do in this case is catch the click event, and try to "guess" which element was clicked. So I have to have some kind of matrix, which stores a link to a tag object for each pixel on the canvas, AND I have to update this matrix on every redraw. Now this sounds incredibly inefficient, and before I even start trying to implement this, I want to ask the community - is there some "well known" algorithm that would help me in this case? Or maybe I'm just missing something, and the answer is right behind the corner? :)

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• Delphi - How to prevent Forms/MsgBoxes to move under prior form?

  - by durumdara

  Hi! Many times we experienced after Windows 98 era that some dialogs are lost their Z-Order, and moved back to prior form. For example: Dialog1.ShowModal; Dialog1.OnClickButton() : ShowMessage('anything'); When MessageBox appears, sometimes not got focus, it is moved under Dialog1. The users confused on it, because they are say: application freezed!!! But if they are uses AltTab to move another app and back, the focus return to the MessageBox, and it will be the foreground Window. We experienced this with ShowMessage, MessageBox, normal forms, QuickReport forms also. Is anyone knows about this? Is it Windows bug? How to prevent it? How to catch this? Thanks for your help: dd

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• How can a client try to reconnect to a server after a first failed try with WCF?

  - by djerry

  Hey guys, I'm using a client - server app. When a client starts, he gets a login-screen. When the server is not up yet, the call to the server will throw an exception which i catch (EndpointNotFoundException). I show a messagebox telling the user the server is offline. When he tries to reconnect again, it will throw another exception (CommunicationObjectFaultedException), even though the server is online. When a new client starts then, he can connect to the server. But the client who attempted before, still gets the error. My question now is how can the first client login after a failed first try without having to start his program again. So i want to clear the communicationchannel of its faulted state or something like that. Thanks in advance.

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• Android Paypal One time Payment

  - by Ameya

  Hi All, Does any one know, or is it possible to do one time payment, with paypal in android ? Consider the senario. Buyer purchases installs free application. Clicks on paypal module and makes in-app payment, purchases feature successfully. Buyer deletes application. All information including the feature purchase enty in database is deleted. Buyer reinstalls the application. Here is the catch, if he wants to use the feature he will have to do a re-purchase. Which I wann to avoid in my application. This is taken care in iPhoen in-app purchase. That is if a buyer has already purchased an feture or in-app item, and if he trys to repurchase it (item has been set to one time payment) , the in-app purchase transaction will succeed without the user actually having to repay for the item. Is there an solution for this can anyone help.

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• Problem at JUnit test with generics

  - by Tom Brito

  In my utility method: public static <T> T getField(Object obj, Class c, String fieldName) { try { Field field = c.getDeclaredField(fieldName); field.setAccessible(true); return (T) field.get(obj); } catch (Exception e) { e.printStackTrace(); fail(); return null; } } The line return (T) field.get(obj); gives the warning "Type safety: Unchecked cast from Object to T"; but I cannot perform instanceof check against type parameter T, so what am I suppose to do here?

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• Zend Framework: how to remove rendered views in the controller?

  - by takpar

  i want to render one of these sets of views: head body-$id1 foot OR head body-$id2 foot which set exsists. i do it like this: try { $this->render("head"); $this->render("body-$id1"); $this->render("foot"); } catch (Exception $e) { $this->render("head"); $this->render("body-$id2"); $this->render("foot"); } but it causes the head view be rendered twice if body-$id1 does not exists. do you have a better solution? in another saying, may i check the existance of body-$id1 before rendering it?

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• Windows Service suddenly doing nothing

  - by TB

  Hi, My windows service is using a Thread (not a timer) which is always looping and sleeps for 1 second every loop using : evet.WaitOne(interval); When I start the service it works fine and I can see in the task manager that it is running, consuming and releasing memory, consuming processor ... etc that is all normal, but after a while (random amount of time) the service simply stops!! it is still there in the task manager but it is not consuming any processor work now and its consumption to the memory is not changing. it simply (died but still there in the task manager like a Zombie). I know that many exceptions might have happened during running the service (it is really doing many things) but all those exceptions are handled in Try catch blocks, so why is my "always looping" thread stops ??? This thread also logs every time he loops, when he is freezig in this way he is not logging anything (of course)

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• C++ Constructor Initializer List - using member functions of initialized members

  - by Andy

  I've run into the following a few times with initializer lists and I've never been able to explain it well. Can anyone explain why exactly the following fails (I don't have a compiler to catch typos, so bear with me): class Foo { public: Foo( int i ) : m_i( i ) {} //works with no problem int getInt() {return m_i;} ~Foo {} private: int m_i; }; class Bar { public: Bar() : m_foo( 5 ), //this is ok m_myInt( m_foo.getInt() ) //runtime error, seg 11 {} ~Bar() {} private: Foo m_foo; int m_myInt; }; When trying to call member functions of members initialized higher up the initializer list, I get seg faults. I seem to recall this is a known problem (or perhaps somehow by design) but I've never seen it well described. The attached example is contrived with plain old data types, but substitute the Bar::m_myInt with another object lacking a default (empty) constructor and the issue is more real. Can anyone enlighten me? Thanks!

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• Compiling a class using Java code using process

  - by Noona

  I have this piece of code that compiles a class called tspClassName, when I compile using this code: Process compileProc = null; try { compileProc = Runtime.getRuntime().exec("javac -classpath ." + File.separator + "src" + File.separator + File.separator + "generated." + tspClassName + ".java -d ." + File.separator + "bin"); // catch exception if (compileProc.exitValue() != 0) { System.out.println("Compile exit status: " + compileProc.exitValue()); System.err.println("Compile error:" + compileProc.getErrorStream()); it outputs this: "Compile exit status: 2 Compile error:java.io.FileInputStream@17182c1" The class tspClassName.java compiles without errors otherwise, so I am guessing it has to do with the path,and in my eclipse project, the tspClassName.java resides in package homework4.generated inside src, is there something wrong with the path that I use in the code? thanks

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• Catching errors in ANTLR and finding parent

  - by Andreas

  I have found out that I can catch errors during parsing by overwriting displayRecognitionError, but how do I find the parent "node" of this error? ex. if I have the grammar: prog: stat expr; stat: STRING; expr: INTEGER; And give it the input "abc def". Then I will get an error at "def" which should be an integer. At this point I then want to get the parent which is "expr" (since it fails inside the INTEGER part) and it's parent "prog". Kind of like printing stack trace in java. I tried to look at the node from RecognitionException parsed to displayRecognitionError, but it is null, and using CommonErrorNode the parent is null. Should I maybe take a completely different approach?

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