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  • Java: exception-throwing class?

    - by HH
    I have classes DirReader and Search. The search uses DirReader. I want the search to know when DirReader throws exception. So how can I have class throwing exception? Currently, I use initCorrect -dummy var. Exception-style method may be more appropriate. Simplified Example Error $ javac ExceptionStatic.java ExceptionStatic.java:4: '{' expected public class ExceptionStatic throws Exception{ ^ 1 error Code import java.util.*; import java.io.*; // THIS PART NEEDS TO BE FIXED: public class ExceptionStatic throws Exception{ private static boolean initCorrect = false; public static String hello; static{ try{ hello = "hallo"; //some other conditionals in real code if( true) throw new Exception(); initCorrect=true; }catch(Exception e){ e.printStackTrace(); } } public static void main(String[] args){ if(initCorrect) System.out.println(hello); } }

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  • JNI_CreateJavaVM: Buffer overrun if I throw an exception in case of failure

    - by Dominik Fretz
    Hi, In a C++ project, I use the JNI invocation API to launch a JVM. I've done a little wrapper arount the JVM so I can use all the needed parts in a OO fashion. So far that works great. Now, if the JVM does not start (JNI_CreateJavaVM returns a value < 0) I'd like to raise an exception within my C++ code.But if I throw an exception after JNI_CreateJavaVM, I get a buffer overrun. If I raise the exception without the JNI_CreateJavaVM call, it works as expected. Does anyone have a clue on what the issue could be here? Or how to debug this? Environment: Windows, Visual Studio 2008 JDK: jrockit27.6jdk16005, but happens with SUN stock one as well Cheers Dominik

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  • Method with throws Exception: Where is it actually handled?

    - by Esq
    Here is an example code, I am throwing an exception here, it works perfectly fine without the try/catch block of code for some reason. Do I have to handle this inside this method "EntryDelete" or Do I have to handle this where the method is called from? If so can I see an example, what do I have to import in there? What is the acceptable syntax or method to do this? public boolean EntryDelete(int entryId) throws SQLException{ this.open(); kDatabase.delete(kENTRY_TABLE, kENTRY_ENTRY_ID + "=" + entryId, null); this.close(); return true; } Thanks

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  • Exception wrapping and HTML pages

    - by dotnetdev
    Hi, We have a sharepoint 2007 project at work. The exception handling policy is to log to the Sharepoint logs. In this case, would the best approach be to call that method and then rethrow the exception higher up? Except if I rethrow it to be caught higher up, there is no other exception handling code so what would happen in this case? Also, if you are going to display a more friendly error to the user (which uses information in the exception object), then this would be a good use of exception wrapping. Would it be a good idea to make a custom aspx page and add these to customerrors, so that on init (not sure of the exact event), I can display exception info in the passed parameter on the page. However, a static html page can't do this so I don't see the point in wrapping exceptions (unless there is a page or alert which uses the exception object). So if a project uses html pages for errors, is there a point in wrapping exceptions? Thanks

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  • Strange IIS/Asp.net Exception Message

    - by Element
    I have a standard asp.net 2.0 application running on IIS 6. I have noticed some strange exception messages in the logs. They seem to be caused by random spam bots trying to submit forms. They are strange because the request string is huge and all the exception details in the event manager are messed up, they have been replaced with %21,%22, etc.. as seen in the screen shot. Is this some kind of exploit or just a bug in the asp.net exception handler/logger ? UPDATE: I traced the requests that are causing this strange log event to a bug in IE8 that causes it to request scriptresource.axd?d={html from page} as described in these links: MS Connect SO - Invalid Webresource.axd SO - IE8 Dropping Memory Pages I am still not sure why these requests would break the IIS log event like seen above, they are just long strings of jiberish being sent to the server, maybe someone reading this can shed some light on it.

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  • Exception handling protocol for methods

    - by athena
    Is there any specific protocol for handling exceptions in public methods? Consider this eg. public int someMethod() { try{ code that might throw an exception } catch(Exception e) { log the exception } } Say that this method might throw an ArrayIndexOutOfBoundsException. So, is it correct to handle this Exception in the method itself (as in the example) or throw it and assume that the calling method will handle the Exception?

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  • Subterranean IL: Filter exception handlers

    - by Simon Cooper
    Filter handlers are the second type of exception handler that aren't accessible from C#. Unlike the other handler types, which have defined conditions for when the handlers execute, filter lets you use custom logic to determine whether the handler should be run. However, similar to a catch block, the filter block does not get run if control flow exits the block without throwing an exception. Introducing filter blocks An example of a filter block in IL is the following: .try { // try block } filter { // filter block endfilter }{ // filter handler } or, in v1 syntax, TryStart: // try block TryEnd: FilterStart: // filter block HandlerStart: // filter handler HandlerEnd: .try TryStart to TryEnd filter FilterStart handler HandlerStart to HandlerEnd In the v1 syntax there is no end label specified for the filter block. This is because the filter block must come immediately before the filter handler; the end of the filter block is the start of the filter handler. The filter block indicates to the CLR whether the filter handler should be executed using a boolean value on the stack when the endfilter instruction is run; true/non-zero if it is to be executed, false/zero if it isn't. At the start of the filter block, and the corresponding filter handler, a reference to the exception thrown is pushed onto the stack as a raw object (you have to manually cast to System.Exception). The allowed IL inside a filter block is tightly controlled; you aren't allowed branches outside the block, rethrow instructions, and other exception handling clauses. You can, however, use call and callvirt instructions to call other methods. Filter block logic To demonstrate filter block logic, in this example I'm filtering on whether there's a particular key in the Data dictionary of the thrown exception: .try { // try block } filter { // Filter starts with exception object on stack // C# code: ((Exception)e).Data.Contains("MyExceptionDataKey") // only execute handler if Contains returns true castclass [mscorlib]System.Exception callvirt instance class [mscorlib]System.Collections.IDictionary [mscorlib]System.Exception::get_Data() ldstr "MyExceptionDataKey" callvirt instance bool [mscorlib]System.Collections.IDictionary::Contains(object) endfilter }{ // filter handler // Also starts off with exception object on stack callvirt instance string [mscorlib]System.Object::ToString() call void [mscorlib]System.Console::WriteLine(string) } Conclusion Filter exception handlers are another exception handler type that isn't accessible from C#, however, just like fault handlers, the behaviour can be replicated using a normal catch block: try { // try block } catch (Exception e) { if (!FilterLogic(e)) throw; // handler logic } So, it's not that great a loss, but it's still annoying that this functionality isn't directly accessible. Well, every feature starts off with minus 100 points, so it's understandable why something like this didn't make it into the C# compiler ahead of a different feature.

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  • Subterranean IL: Exception handler semantics

    - by Simon Cooper
    In my blog posts on fault and filter exception handlers, I said that the same behaviour could be replicated using normal catch blocks. Well, that isn't entirely true... Changing the handler semantics Consider the following: .try { .try { .try { newobj instance void [mscorlib]System.Exception::.ctor() // IL for: // e.Data.Add("DictKey", true) throw } fault { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } } filter { ldstr "2a: Filter logic" call void [mscorlib]System.Console::WriteLine(string) // IL for: // (bool)((Exception)e).Data["DictKey"] endfilter }{ ldstr "2b: Filter handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } } catch object { ldstr "3: Catch handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } Return: // rest of method If the filter handler is engaged (true is inserted into the exception dictionary) then the filter handler gets engaged, and the following gets printed to the console: 2a: Filter logic 1: Fault handler 2b: Filter handler and if the filter handler isn't engaged, then the following is printed: 2a:Filter logic 1: Fault handler 3: Catch handler Filter handler execution The filter handler is executed first. Hmm, ok. Well, what happens if we replaced the fault block with the C# equivalent (with the exception dictionary value set to false)? .try { // throw exception } catch object { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) rethrow } we get this: 1: Fault handler 2a: Filter logic 3: Catch handler The fault handler is executed first, instead of the filter block. Eh? This change in behaviour is due to the way the CLR searches for exception handlers. When an exception is thrown, the CLR stops execution of the thread, and searches up the stack for an exception handler that can handle the exception and stop it propagating further - catch or filter handlers. It checks the type clause of catch clauses, and executes the code in filter blocks to see if the filter can handle the exception. When the CLR finds a valid handler, it saves the handler's location, then goes back to where the exception was thrown and executes fault and finally blocks between there and the handler location, discarding stack frames in the process, until it reaches the handler. So? By replacing a fault with a catch, we have changed the semantics of when the filter code is executed; by using a rethrow instruction, we've split up the exception handler search into two - one search to find the first catch, then a second when the rethrow instruction is encountered. This is only really obvious when mixing C# exception handlers with fault or filter handlers, so this doesn't affect code written only in C#. However it could cause some subtle and hard-to-debug effects with object initialization and ordering when using and calling code written in a language that can compile fault and filter handlers.

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  • Exception Handling And Other Contentious Political Topics

    - by Justin Jones
    So about three years ago, around the time of my last blog post, I promised a friend I would write this post. Keeping promises is a good thing, and this is my first step towards easing back into regular blogging. I fully expect him to return from Pennsylvania to buy me a beer over this. However, it’s been an… ahem… eventful three years or so, and blogging, unfortunately, got pushed to the back burner on my priority list, along with a few other career minded activities. Now that the personal drama of the past three years is more or less resolved, it’s time to put a few things back on the front burner. What I consider to be proper exception handling practices is relatively well known these days. There are plenty of blog posts out there already on this topic which more or less echo my opinions on this topic. I’ll try to include a few links at the bottom of the post. Several years ago I had an argument with a co-worker who posited that exceptions should be caught at every level and logged. This might seem like sanity on the surface, but the resulting error log looked something like this: Error: System.SomeException Followed by small stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace.   These were all the same exception. The problem with this approach is that the error log, if you run any kind of analytics on in, becomes skewed depending on how far up the stack trace your exception was thrown. To mitigate this problem, we came up with the concept of the “PreLoggedException”. Basically, we would log the exception at the very top level and subsequently throw the exception back up the stack encapsulated in this pre-logged type, which our logging system knew to ignore. Now the error log looked like this: Error: System.SomeException Followed by small stack trace. Much cleaner, right? Well, there’s still a problem. When your exception happens in production and you go about trying to figure out what happened, you’ve lost more or less all context for where and how this exception was thrown, because all you really know is what method it was thrown in, but really nothing about who was calling the method or why. What gives you this clue is the entire stack trace, which we’re losing here. I believe that was further mitigated by having the logging system pull a system stack trace and add it to the log entry, but what you’re actually getting is the stack for how you got to the logging code. You’re still losing context about the actual error. Not to mention you’re executing a whole slew of catch blocks which are sloooooooowwwww……… In other words, we started with a bad idea and kept band-aiding it until it didn’t suck quite so bad. When I argued for not catching exceptions at every level but rather catching them following a certain set of rules, my co-worker warned me “do yourself a favor, never express that view in any future interviews.” I suppose this is my ultimate dismissal of that advice, but I’m not too worried. My approach for exception handling follows three basic rules: Only catch an exception if 1. You can do something about it. 2. You can add useful information to it. 3. You’re at an application boundary. Here’s what that means: 1. Only catch an exception if you can do something about it. We’ll start with a trivial example of a login system that uses a file. Please, never actually do this in production code, it’s just concocted example. So if our code goes to open a file and the file isn’t there, we get a FileNotFound exception. If the calling code doesn’t know what to do with this, it should bubble up. However, if we know how to create the file from scratch we can create the file and continue on our merry way. When you run into situations like this though, What should really run through your head is “How can I avoid handling an exception at all?” In this case, it’s a trivial matter to simply check for the existence of the file before trying to open it. If we detect that the file isn’t there, we can accomplish the same thing without having to handle in in a catch block. 2. Only catch an exception if you can do something about it. Continuing with the poorly thought out file based login system we contrived in part 1, if the code calls a Login(…) method and the FileNotFound exception is thrown higher up the stack, the code that calls Login must account for a FileNotFound exception. This is kind of counterintuitive because the calling code should not need to know the internals of the Login method, and the data file is an implementation detail. What makes more sense, assuming that we didn’t implement any of the good advice from step 1, is for Login to catch the FileNotFound exception and wrap it in a new exception. For argument’s sake we’ll say LoginSystemFailureException. (Sorry, couldn’t think of anything better at the moment.) This gives us two stack traces, preserving the original stack trace in the inner exception, and also is much more informative to the calling code. 3. Only catch an exception if you’re at an application boundary. At some point we have to catch all the exceptions, even the ones we don’t know what to do with. WinForms, ASP.Net, and most other UI technologies have some kind of built in mechanism for catching unhandled exceptions without fatally terminating the application. It’s still a good idea to somehow gracefully exit the application in this case if possible though, because you can no longer be sure what state your application is in, but nothing annoys a user more than an application just exploding. These unhandled exceptions need to be logged, and this is a good place to catch them. Ideally you never want this option to be exercised, but code as though it will be. When you log these exceptions, give them a “Fatal” status (e.g. Log4Net) and make sure these bugs get handled in your next release. That’s it in a nutshell. If you do it right each exception will only get logged once and with the largest stack trace possible which will make those 2am emergency severity 1 debugging sessions much shorter and less frustrating. Here’s a few people who also have interesting things to say on this topic:  http://blogs.msdn.com/b/ericlippert/archive/2008/09/10/vexing-exceptions.aspx http://www.codeproject.com/Articles/9538/Exception-Handling-Best-Practices-in-NET I know there’s more but I can’t find them at the moment.

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  • C# Throw Exception on use Assert?

    - by guazz
    I have a system where the employeeId must alway exist unless there is some underlying problem. The way I see it, is that I have two choices to check this code: 1: public void GetEmployee(Employee employee) { bool exists = EmployeeRepository.VerifyIdExists(Employee.Id); if (!exists) { throw new Exception("Id does not exist); } } or 2: public void GetEmployee(Employee employee) { EmployeeRepository.AssertIfNotFound(Employee.Id); } Is option #2 acceptable in the C# language? I like it because it's tidy in that i don't like looking at "throw new Exception("bla bla bla") type messages outsite the class scope.

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  • Is there any reason to throw a DivideByZeroException?

    - by Atomiton
    Are there any cases when it's a good idea to throw errors that can be avoided? I'm thinking specifically of the DivideByZeroException and NullReferenceException For example: double numerator = 10; double denominator = getDenominatorFromUser(); if( denominator == 0 ){ throw new DivideByZeroException("You can't divide by Zero!"); } Are there any reasons for throwing an error like this? NOTE: I'm not talking about catching these errors, but specifically in knowing if there are ever good reasons for throwing them.

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  • Are there legitimate reasons for returning exception objects instead of throwing them?

    - by stakx
    This question is intended to apply to any OO programming language that supports exception handling; I am using C# for illustrative purposes only. Exceptions are usually intended to be raised when an problem arises that the code cannot immediately handle, and then to be caught in a catch clause in a different location (usually an outer stack frame). Q: Are there any legitimate situations where exceptions are not thrown and caught, but simply returned from a method and then passed around as error objects? This question came up for me because .NET 4's System.IObserver<T>.OnError method suggests just that: exceptions being passed around as error objects. Let's look at another scenario, validation. Let's say I am following conventional wisdom, and that I am therefore distinguishing between an error object type IValidationError and a separate exception type ValidationException that is used to report unexpected errors: partial interface IValidationError { } abstract partial class ValidationException : System.Exception { public abstract IValidationError[] ValidationErrors { get; } } (The System.Component.DataAnnotations namespace does something quite similar.) These types could be employed as follows: partial interface IFoo { } // an immutable type partial interface IFooBuilder // mutable counterpart to prepare instances of above type { bool IsValid(out IValidationError[] validationErrors); // true if no validation error occurs IFoo Build(); // throws ValidationException if !IsValid(…) } Now I am wondering, could I not simplify the above to this: partial class ValidationError : System.Exception { } // = IValidationError + ValidationException partial interface IFoo { } // (unchanged) partial interface IFooBuilder { bool IsValid(out ValidationError[] validationErrors); IFoo Build(); // may throw ValidationError or sth. like AggregateException<ValidationError> } Q: What are the advantages and disadvantages of these two differing approaches?

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  • flex blazeds spring exception translator

    - by Shah Al
    I am using spring exception translator to wrap java exception into flex exception. eg public void testException()throws Exception{ throw new Exception("my exception"); } But for some reason, I am getting IllegalAccessError. The code sections are entering the testException and the Translator class. Question: why it trying to get log target level ? Can someone help me resolve this please. Below is the lines from the log: MyExceptionTranslatorImpl.translate()class java.lang.IllegalAccessError MyExceptionTranslatorImpl.translate()java.lang.IllegalAccessError: tried to access method flex.messaging.log.Log.getTargetLevel()S from class flex.messaging.MessageException MyExceptionTranslatorImpl.translate()tried to access method flex.messaging.log.Log.getTargetLevel()S from class flex.messaging.MessageException [BlazeDS] tried to access method flex.messaging.log.Log.getTargetLevel()S from class flex.messaging.MessageException [BlazeDS] Serializing AMF/HTTP response

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  • HttpWebRequest.GetResponse() - what specific status codes cause an exception to be thrown?

    - by H. Morrow
    I've hunted around for some definitive documentation on this but haven't had much luck finding any. Basically - the question is - for which HTTP Status codes coming back from the server will HttpWebRequest.GetResponse() generate a WebException after doing something like say, a POST? Specifically - will it generate a WebException for anything other than status 200 OK? Or will it only generate a WebException for say, 400, 404, and 500 (for the sake of argument). I want to know since, the server I'm communicating with defines anything other than HTTP 200 OK coming back as an error condition - and the key is, can I rely on a WebException being generated for anything other than 200? (I've currently written my code so that it'll actually check the return status code everytime to ensure it's 200 OK and if it's not, take appropriate action - but it's alot of duplication between that, and the catch block for a WebException, and I'm hoping to clean it up...) Any relevant links to documentation would be most appreciated. Thanks!

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  • Actionscript 3.0 - drag and throw with easing

    - by Joe Hamilton
    I'm creating a map in flash and I would like to have a smooth movement similar to this: http://www.conceptm.nl/ I have made a start but I'm having trouble taking it to the next stage. My code currently throws the movieclip after the mouse is release but there is no easing while the mouse button is down. Any tips on how I would achieve this? Here is my current code: // Vars var previousPostionX:Number; var previousPostionY:Number; var throwSpeedX:Number; var throwSpeedY:Number; var isItDown:Boolean; // Event Listeners addEventListener(MouseEvent.MOUSE_DOWN, clicked); addEventListener(MouseEvent.MOUSE_UP, released); // Event Handlers function clicked(theEvent:Event) { isItDown =true; addEventListener(Event.ENTER_FRAME, updateView); } function released(theEvent:Event) { isItDown =false; } function updateView(theEvent:Event) { if (isItDown==true){ throwSpeedX = mouseX - previousPostionX; throwSpeedY = mouseY - previousPostionY; mcTestMovieClip.x = mouseX; mcTestMovieClip.y = mouseY; } else{ mcTestMovieClip.x += throwSpeedX; mcTestMovieClip.y += throwSpeedY; throwSpeedX *=0.9; throwSpeedY *=0.9; } previousPostionX= mcTestMovieClip.x; previousPostionY= mcTestMovieClip.y; }

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  • Should Java IOException have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling this exception to a separate system error handler.

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  • Why does a looser specification in an overriding method compile after the exception specification fo

    - by Everyone
    The code below has an overridden method with a looser exception specification as compared to the method being overridden. //AnotherMain.java public class AnotherMain { public void dummyMethod( String args[] ) throws IOException{ throw new IOException(); } } //SubAnotherMain.java public class SubAnotherMain extends AnotherMain{ @Override public void dummyMethod( String[] args ) throws Exception { // To get this to compile, change the above - throws IOException, Exception super.dummyMethod(args); throw new Exception("This will not compile unless the exception specification has IOException too"); } } Afaik, the overriding method should not compile at all as the looser specification might break substitutability. Why does it compile after the original exception specification is included in the override? What have I misunderstood?

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  • Python: User-Defined Exception That Proves The Rule

    - by bandana
    Python documentations states: Exceptions should typically be derived from the Exception class, either directly or indirectly. the word 'typically' leaves me in an ambiguous state. consider the code: class good(Exception): pass class bad(object): pass Heaven = good() Hell = bad() >>> raise Heaven Traceback (most recent call last): File "<pyshell#163>", line 1, in <module> raise Heaven good >>> raise Hell Traceback (most recent call last): File "<pyshell#171>", line 1, in <module> raise Hell TypeError: exceptions must be classes or instances, not bad so when reading the python docs, should i change 'typically' with ''? what if i have a class hierarchy that has nothing to do with the Exception class, and i want to 'raise' objects belonging to the hierarchy? i can always raise an exception with an argument: raise Exception, Hell This seems slightly awkward to me What's so special about the Exception class, that only its family members can be raised?

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  • Should class IOException in Java have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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  • Exception and Inheritance in JAVA

    - by user1759950
    Suppose we have this problem public class Father{ public void method1(){...} } public class Child1 extends Father{ public void method1() throws Exception{ super.method1(); ... } } Child1 extends Father and override method1 but given implementation Child1.method1 now throws a exception, this wont compile as override method can't throw new exceptions. What is the best solution? Propagate the required exception to the Father.. to me this is against encapsulation, inheritance and general OOP ( the father potentially throw and exception that will never happen ) Use a RuntimeException instead? This solution wont propagate the Exception to the father but I read In Oracle docs and others sources states class of exceptions should be used when "Client code cannot do anything" this is not that case, this exception will b useful to recover blablabla ( why is wrong to use RuntimeException instead? ) Other.. thanks, Federico

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  • C++ - Where to throw exception?

    - by HardCoder1986
    Hello! I have some kind of an ideological question, so: Suppose I have some templated function template <typename Stream> void Foo(Stream& stream, Object& object) { ... } which does something with this object and the stream (for example, serializes that object to the stream or something like that). Let's say I also add some plain wrappers like (and let's say the number of these wrappers equals 2 or 3): void FooToFile(const std::string& filename, Object& object) { std::ifstream stream(filename.c_str()); Foo(stream, object); } So, my question is: Where in this case (ideologically) should I throw the exception if my stream is bad? Should I do this in each wrapper or just move that check to my Foo, so that it's body would look like if (!foo.good()) throw (something); // Perform ordinary actions I understand that this may be not the most important part of coding and these solutions are actually equal, but I just wan't to know "the proper" way to implement this. Thank you.

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  • C++ Exceptions and Inheritance from std::exception

    - by fbrereto
    Given this sample code: #include <iostream> #include <stdexcept> class my_exception_t : std::exception { public: explicit my_exception_t() { } virtual const char* what() const throw() { return "Hello, world!"; } }; int main() { try { throw my_exception_t(); } catch (const std::exception& error) { std::cerr << "Exception: " << error.what() << std::endl; } catch (...) { std::cerr << "Exception: unknown" << std::endl; } return 0; } I get the following output: Exception: unknown Yet simply making the inheritance of my_exception_t from std::exception public, I get the following output: Exception: Hello, world! Could someone please explain to me why the type of inheritance matters in this case? Bonus points for a reference in the standard.

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  • [C#] how to do Exception Handling & Tracing

    - by shrimpy
    Hi all, i am reading some C# books, and got some exercise don't know how to do, or not sure what does the question mean. Problem: After working for a company for some time, your skills as a knowledgeable developer are recognized, and you are given the task of “policing” the implementation of exception handling and tracing in the source code (C#) for an enterprise application that is under constant incremental development. The two goals set by the product architect are: 100% of methods in the entire application must have at least a standard exception handler, using try/catch/finally blocks; more complex methods must also have additional exception handling for specific exceptions All control flow code can optionally write “tracing” information to assist in debugging and instrumentation of the application at run-time in situations where traditional debuggers are not available (eg. on staging and production servers). (i am not quite understand these criterias, i came from the java world, java has two kind of exception, check and unchecked exception. Developer must handle checked exception, and do logging. about unchecked exception, still do logging maybe, but most of the time we just throw it. however here comes to C#, what should i do????) Question for Problem: List rules you would create for the development team to follow, and the ways in which you would enforce rules, to achieve these goals. How would you go about ensuring that all existing code complies with the rules specified by the product architect; in particular, what considerations would impact your planning for the work to ensure all existing code complies?

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  • Multiple Exception Handling in one if statement [closed]

    - by JA3N
    I am having trouble with throwing and catching exceptions. Here is the code for assignSeat(), assignSeat is called in a try block in another class. void assignSeat(String passengerName, int x, int y) throws SeatOccupiedException, InvalidPassengerNameException { Seat tSeat = airplane.getSeat(x,y); if (tSeat!=null) { if (passengerName.isEmpty() || !passengerName.matches("[a-zA-Z]+")) { throw new InvalidPassengerNameException(); } //excluded else if else if (foundPassenger(passengerName)) { airplane.seatList.get(airplane.seatNumber(passengerName)).unOccupy(); tSeat.occupy(); for (int i = 0; i<passengers.size();i++) if (passengers.get(i).getName().equals(passengerName)) passengers.get(i).changeSeat(tSeat.getSeatName()); } else if (!tSeat.occupied) { tSeat.occupy(); addPassenger(passengerName, tSeat.getSeatName()); } else if (tSeat.occupied) { throw new SeatOccupiedException(); } } and here is the code that calls assignSeat() and is in another class (I won't copy the whole class to make it look clearer) if (afComp.currentAF != null) { try { afComp.currentAF.assignSeat(nameField.getText(), x, y); //<-Problem here, "Unhandled exception type SeatOccupiedException" } catch (SeatOccupiedException exception) //<-Problem here, "Unreachable catch block, This exception is never thrown from the try statement body" { } catch(InvalidPassengerNameException exception) //<-No problems. { } } Whats wrong with the try block? why won't it throw the SeatOccupiedException? Exception classes: SeatOccupied: package a2; public class SeatOccupiedException extends Exception { public SeatOccupiedException(){} } InvalidPassengerName: package a2; public class InvalidPassengerNameException extends Exception { public InvalidPassengerNameException() {} } Every class I have is in package a2 imports for class that calls assignSeat package a2; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.MouseListener; import java.awt.event.MouseMotionListener; import java.awt.event.MouseEvent; import java.awt.BorderLayout; import javax.swing.*; import javax.swing.event.*; imports for class that has assignSeat package a2; import java.util.ArrayList;

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