try-catch

问题 I have a question about downloading files. I know how to download files, using the download.file function. I need to download multiple files from a particular site, each file corresponding to a different date. I have a series of dates, using which I can prepare the URL to download the file. I know for a fact that for some particular dates, the files are missing on the website. Subsequently my code stops at that point. I then have to manually reset the date index (increment it by 1) and re-run

问题 I have a loop where I call stored procedure with different parameter value. Next call cmd.ExecuteNonQuery(); I use transaction to save all or rollback, and checkBox2 - save always. I found one problem and I can't find solution. After first problem when catch block is fired transaction object loses its connection. t.connection is null! Everything is good but transaction object is without connection at start it has! try { while (!sr.EndOfStream) { strLine.Remove(0, strLine.Length); //c = sr

问题 I came across this article about detecting VMWare or Virtual PC http://www.codeproject.com/KB/system/VmDetect.aspx and I saw that they use some kind of try-except statement. So I looked it up in the MSDN: http://msdn.microsoft.com/en-us/library/s58ftw19%28v=vs.80%29.aspx and I don't understand why would I use a try-except instead of the good old try-catch. does it just give me additional information about the exception? If so, I can use a try-catch when I use the code from the attached

问题 Why doesn't the subroutine with try/catch give me the same results as the eval-version does? #!/usr/bin/env perl use warnings; use strict; use 5.012; use Try::Tiny; sub shell_command_1 { my $command = shift; my $timeout_alarm = shift; my @array; eval { local $SIG{ALRM} = sub { die "timeout '$command'\n" }; alarm $timeout_alarm; @array = qx( $command ); alarm 0; }; die $@ if $@ && $@ ne "timeout '$command'\n"; warn $@ if $@ && $@ eq "timeout '$command'\n"; return @array; } shell_command_1(

问题 I have a try - catch block that I wish to break like a switch block but I couldn't find a recommended way of doing it. I'm fetching a lot of data in the try - catch block and wish to stop the fetching in between in case a certain condition is met. Just to get it working for now, I've deliberately forced the code to go into the catch block: int i=0; try { //--do stuff---- if(//-------is condition met?--------//) i = 1/0; // divide 1 by 0 -- a definite exception } catch (Exception e) {//-------

问题 I understand that try and catch() are used for exception handling, just in case an error or crash would occur in the program under certain cases. I also understand how they work. But why use try and catch() ? Why not just use an if() statement that looks for a certain case and if that case is true, it does cout << //error code ? 回答1: Exception handling: can be used with constructors and operators that have no opportunity to return a separate error code (they could set the object into some

问题 I'd like a response from someone who actually does real-time programming in C# or who really understands the language internals. I know that exceptions should not be used to handle normal processing, but only to detect error conditions. There is plenty of discussion on that topic. I'd like to know if there is any run time slow-down from simply having a try/catch block in place (which never catches an exception unless the program will have to end anyway). The try/catch block is inside a

问题 I'm trying to do the following: try { // just an example $time = 'wrong datatype'; $timestamp = date("Y-m-d H:i:s", $time); } catch (Exception $e) { return false; } // database activity here In short: I initialize some variables to be put in the database. If the initialization fails for whatever reason - e.g. because $time is not the expected format - I want the method to return false and not input wrong data into the database. However, errors like this are not caught by the 'catch'-statement

问题 My program has an endless loop, when I use try and catch block in a while loop . import java.util.*; class Try { public static void main(String args[]) { Scanner sc=new Scanner(System.in); while(true) { try { System.out.println("Enter a no "); int s=sc.nextInt(); } catch(Exception e) { System.out.println("Invalid input try again"); } } } } When I input an integer, it runs fine and asks for another input, but when I input a char, it goes for endless loop. Why is this so? 回答1: Your program

问题 My program has an endless loop, when I use try and catch block in a while loop . import java.util.*; class Try { public static void main(String args[]) { Scanner sc=new Scanner(System.in); while(true) { try { System.out.println("Enter a no "); int s=sc.nextInt(); } catch(Exception e) { System.out.println("Invalid input try again"); } } } } When I input an integer, it runs fine and asks for another input, but when I input a char, it goes for endless loop. Why is this so? 回答1: Your program