try-catch

问题 Fairly new to Java and am trying to better understand a few things. I understand that try/catch statement variables only have scope within that statement. I am trying to learn java db sql and am running into an issue. final String DB_URL = "jdbc:derby://localhost:1527/Customers"; Connection conn = DriverManager.getConnection(DB_URL); This creates the connection with my database. I need to have this in a try/catch statement. I want to access the conn variable again at the end of the program to

问题 Fairly new to Java and am trying to better understand a few things. I understand that try/catch statement variables only have scope within that statement. I am trying to learn java db sql and am running into an issue. final String DB_URL = "jdbc:derby://localhost:1527/Customers"; Connection conn = DriverManager.getConnection(DB_URL); This creates the connection with my database. I need to have this in a try/catch statement. I want to access the conn variable again at the end of the program to

问题 I have an internet operation that reads line from an online file. It is in a try-catch block. When the execution fails (for example for the missing internet connection) the operation go to catch block and the App crashes. How can I avoid crashes? try { BufferedReader reader = new BufferedReader(new InputStreamReader((new URL(MegaMethods.url+params[0])).openStream()), 8192); String line; while ((line = reader.readLine()) != null) { count++; } reader.close(); } catch (Exception e){ // Here I

问题 Experimenting with using classes in powershell, I'm uncertain how to display output. For instance in this code block the write-error does not display the error message: class Test { [string] $test Test ([string] $test) { $this.test = $test } [test] Testfail() { try { Get-Childitem F:\ -ErrorAction stop } catch { Write-Host "ERROR!!! $this.test" Exit 1 } return $this.test + "not an error!" } } In this case it's is obvious that the code runs the catch statement as the powershell window exits

问题 Experimenting with using classes in powershell, I'm uncertain how to display output. For instance in this code block the write-error does not display the error message: class Test { [string] $test Test ([string] $test) { $this.test = $test } [test] Testfail() { try { Get-Childitem F:\ -ErrorAction stop } catch { Write-Host "ERROR!!! $this.test" Exit 1 } return $this.test + "not an error!" } } In this case it's is obvious that the code runs the catch statement as the powershell window exits

问题 I am trying to write a program that reads numbers input by the user until the user types done. If the user types a non-number other than "done," I want to return an error message like "please enter a number number. When the user types "done", I want to calculate the total of the numbers, the number count and the average. I have tried to create a while loop with try and except to catch the non-numeric error other than done. That is part of the trick, a string entry is an error unless the

问题 I am trying to write a program that reads numbers input by the user until the user types done. If the user types a non-number other than "done," I want to return an error message like "please enter a number number. When the user types "done", I want to calculate the total of the numbers, the number count and the average. I have tried to create a while loop with try and except to catch the non-numeric error other than done. That is part of the trick, a string entry is an error unless the

问题 I have the following (SQL Server 2005) DECLARE @L_ID_FOO_BAR INT BEGIN TRY SELECT @L_ID_FOO_BAR = IDFOO FROM BAR WHERE IDFOO = 5 END TRY BEGIN CATCH SELECT @L_ID_FOO_BAR = NULL END CATCH in the BAR table I could have (on old databases) or not (in some more recennt databases) the IDFOO column. So, for the missing IDFOO column I'd like to leave @L_ID_FOO_BAR = NULL, in case if that column exists select the respective IDFOO. However, when executing the script on bases without that column I

问题 I have the following (SQL Server 2005) DECLARE @L_ID_FOO_BAR INT BEGIN TRY SELECT @L_ID_FOO_BAR = IDFOO FROM BAR WHERE IDFOO = 5 END TRY BEGIN CATCH SELECT @L_ID_FOO_BAR = NULL END CATCH in the BAR table I could have (on old databases) or not (in some more recennt databases) the IDFOO column. So, for the missing IDFOO column I'd like to leave @L_ID_FOO_BAR = NULL, in case if that column exists select the respective IDFOO. However, when executing the script on bases without that column I

问题 Is it possible to execute certain commands in case of error when using tryCatch in R ? I am using the code below but it does not execute X = alternative_value tryCatch( { X = certain_function_that_sometimes_returns_error }, error=function(e) { X = alternative_value }) 回答1: Assign your tryCatch directly to x foo <- function() stop("hello") bar <- function() 'world' x <- tryCatch( { foo() }, error = function(e){ bar() } ) x # [1] "world" 来源： https://stackoverflow.com/questions/43380908/trycatch