Try - catch question..

hello..
i was wondering if i can use a try-block and catch a built in exception without explicitly throwing the exception..
example:
try{
foo[5] = 'A';
catch (IndexOutOfBoundsException e)
{ blah blah
is this possible w/o throwing the IndexOut... exception in the try statement?

You can only catch those exceptions that are (or could be) thrown. The reason your code snippet works is that the exception you're catching is a subclass of RuntimeException. You can always catch any RuntimeException and the compiler will OK it, and you don't have to declare them as being thrown either. If you try to catch an Exception that isn't a RuntimeException (like java.lang.Exception) and isn't thrown, you'll get a compile error. That said, I agree that this isn't the way to do it here.

Similar Messages

Yet another Try Catch question. Iterating through a ForEach loop

Confused on error handling in a Powershell ForEach loop. I’m looping through a list of registry keys, attempting
to open each one. If it succeeds, I do a bunch of stuff. If it fails, I want to skip to the next iteration.
If I was doing It in VBScript I’d do this:
For Each Thing In colThings
Open Thing
If Err.Number <> 0 Then
“oops”
Else
Do stuff
Do stuff
Do stuff
End If
Next
This is what I came up with in PowerShell. It seems to work, but just doesn’t seem powershell-ish. There must be a better way to use the catch output than just creating a $return variable and assigning it success or fail?
ForEach ($subKeyName in $subKeyNames)
try{$subKey = $baseKey.OpenSubKey("$subKeyName")}
catch{$return = "error" }
If($return -eq "error" )
“Oops”
Else
Do stuff
Do stuff
Do Stuff

I totally get what you're saying about formatting. I don't' have any habits yet, since I've only been working in Powershell since... well, what time is it now?
Unfortunately, It Has Been Decreed that we are no longer to use VBScript for any engineering solutions at work, so my 15 years experience in it now needs to be transitioned over asap. I don't have the luxury of crawling before I run. I'm trying not to be
frustrated, but it's like an English major waking up one day and being told "You must now speak French exclusively. Here's a book."
The Do Stuff example of my ForEach loop is about 50 lines of code involving matching values in subkeys of this registry key with another and collecting output. I tried wrapping the whole thing in a try section based on some examples, but it seemed odd, that's
why I'm asking. I'm used to tightly focused error handling at the point where an error may occur.
In this example I'm only interested in whether or not I can open the subkey (it exists, but I may not have permission). If I can't, there's no point in continuing with this iteration of the loop, I want to skip to the next one. So why include all the "Do
Stuff" in the the try section? From a readability viewpoint, it doesn't seem helpful.
Also, there may be more error handling deeper in the code. If I then put that in a try/catch, and then something else inside that, now I have nested try/catches mixed in with nested if/elses, all wrapped in a For loop.
Again, I can see how it works logically, but for readability not so much, and having all these braces 50 lines apart to match up is giving me eye strain :).
It sounds like David is agreeing with jrv, that putting the entire ForEach loop code into a try/catch is the conventional way to do it. I guess it makes as much sense as putting it all in an If-else-Endif, and I just need to adjust my paradigm.
But if not, my specific question was more along the lines of, is there a built in way to tell that the catch section has been executed, rather than me using it to populate an arbitrary variable and then read it? In VBScript, you execute something, and the
next line, you check the Err.number. I wasn't sure if you could do that with a try/catch.

Some simple question , but i dont know...try & catch ..

Hi i was working on a media player and i've faced some problems...like what exactly does the try&catch do ??
and in the Player class what the realize() and prefetch do ??
Thank you in advance..
Mulham Haffar

If you are in doubt when or what exceptions to catch, use the java compiler as your guide. You will get compile time errors that clearly name the exception you have to catch with the line of code that could cause the exception/error. Then do the following:
try {
// the code that could throw the exception
} catch ([the-name-exception] e) {
e.printStackTrace();
// or do something else relevant here - this code gets executed when the exception is thrown
} finally {
// this is an optional block that is always executed before returning from the method (even if there was an exception thrown - do stuff like closing resources here
}where [the-name-exception] is the exception class I mentioned earlier.
You can also declare a method to throw the exception if you don't want to catch it. Just use the keyword "throws" followed by the class name of the exception. Then any place where you call the method will have to catch the exception.
You can also find out what exceptions are being thrown by looking in the JavaDocs. There is plenty more, but that is what you will need to get your program compiling.

Newbie question: Try Catch EndTry....what to catch??

I have a string which is supposed to contain only numeric characters like 1234...
But if unfortunately it contains some alphabet, my program will crash.
I am going to implement a try catch endtry to prevent this. But I don't know what to catch. It can be compiled, but I am just not sure whether it is correct or not.
Currently, I catch CX_STATIC_CHECK.
Is this correct? Please advice me and I will reward you.
Thanks

|ook in st22 to find out the class exception. This is the one you need to catch.
Example:
class exception = cx_division_by_zero.
data: lr_error type ref to cx_division_by_zero.
try.
x = y / z.
catch cx_division_by_zero into lr_error.
endtry.
Edited by: Micky Oestreich on May 14, 2008 6:25 AM

How to get the returned error messages in the Try/Catch block in DS 3.0?

A customer sent me the following questions when he tried to implement custom error handling in DS 3.0. I could only find the function "smtp_to" can return the last few lines of trace or error log file but this is not what he wants. Does anyone know the answers? Thanks!
I am trying to implement the Try/Catch for error handling, but I have
hard time to get the return the msg from DI, so I can write it to out
custom log table.
Can you tell me or point me to sample code that can do this, also, can
you tell me which tables capture these info if I want to query it from
DI system tables

Hi Larry,
In Data Services XI 3.1 (GAd yesterday) we made several enhancements for our Try/Catch blocks. One of them is the additional of functions to get details on the error that was catched :
- error_message() Returns the error message of the caught exception
- error_number() Returns the error number of the caught exception
- error_timestamp() Returns the timestamp of the caught exception.
- error_context() Returns the context of the caught exception. For example, "|Session Datapreview_job|Dataflow debug_DataFlow|Transform Debug"
In previous versions, the only thing you could do was in the mail_to function specify the number of lines you want to include from the error_log, which would send the error_log details in the body of the mail.
Thanks,
Ben.

Can we have try/catch in a static block in a class?

hi All
i have a question about put a try/catch block in a static block in a class to catch exceptions that maybe thrown from using System.xxxx(). in my custom class, i have a static block to initialize some variables using System.xxx(). in case of any error/exception, i need to be able to catch it and let the caller know about it. i tried to put a try/catch block in the static block, and tried to rethrow the exception. but it is not allowed, how would i handle situation like this? thanks for your help and advise in advance.

You could just swallow the exception inside try/catch
block, and instead of throwing it out, just set a
static variable to allow checking from outside
whether the initialization succeeded, or check within
the constructor / methods of this class for
successful initialization, and throw the exception
then. You could even save that exception in a static
variable for later.Ouch, ouch, you're hurting my brain. This would allow someone to ignore a (presumably) fatal error. Throw a RuntimeException as indicated. You can wrap a checked exception in an unchecked one if need be.

Performance impact on using too much try catch block

I have several questions here:
1. The system that I'm developing requires to be high performance, but I am not sure how will try catch block affect overall performance.
2. I wanted to know which would be more efficient (result in faster processing)
Have several generic try catch OR catch all exceptions individually?
ex:
try {
} catch (Exception e){
}vs.
try{
} catch (MalformedUrlException me){
} catch(SQLException){
}3. Which one would be faster, one big try catch block or several small try catch blocks?
ex.
try{
//read from io file
//query database
//parse data
//write to file
//query database again
} catch(Exception e){
//log exception
}vs.
try{
//read from io file
} catch(FileNotFoundException fnfe){
//log exception
try{
//query database
}catch(SQLException se){
//log exception
try{
//parse data
}catch(SaxParserException saxe){
//log exception
try{
//query database again
}catch(SQLException se2){
//log exception
try{
//write to file
} catch(FileNotFoundException fnfe){
//log exception

1. The system that I'm developing requires to be high performance, but I am not sure how will try catch block affect overall performance.Compared to what? You can't write an equivalent program that doesn't have a try-catch block, so the answer would have to be that it doesn't affect performance at all.
2. I wanted to know which would be more efficient (result in faster processing)Have several generic try catch OR catch all exceptions individually?
You still have it backwards. Do you need to do different things for different exceptions? If so, then that's what you have to do and there is no other code that might be "faster".
Here's what you should do. Write the code that needs to be written. Don't leave out necessary stuff because of performance reasons. (If you left out all your code, the program would run much faster.) Then find out which parts of the program ACTUALLY take the most time and work on speeding them up.

Escaping Boolean & Try/Catch blocks

Hi everyone-
You all have been so great. I finally got my double/int and all working on my calculator. Now, I have one more question that I cannot figure out. My booleans to escape when form is not completed correctly are not working. That is, it will output error, but then still attempt the rest, giving printouts/general exception. I tried using another boolean, but not working. Here is the applet:
www.quiltpox.com/HSTCalc.html
and code: www.quiltpox.com/HSTCalc.java
   public void actionPerformed(ActionEvent evt) { //1
                 //declarations
         try{
          //reset all fields to null so user can start over
          if(source == button1)
               text1.setText("");
               text2.setText("");
               text3.setText("");
          if(source == button2)
               //check that all fields have been completed
               if(t1.length() == 0 || t2.length() == 0 || t3.length() == 0)
                        output.append("\nPlease complete the required fields and try again.");
                        verify = false;
               //parse string into integer data and verify
               if(verify)
               //parsing
               if(size == 0 || numOfSquares == 0 || WOF == 0)
                    output.append("\nYou have entered a null value for Square Size, " +
                         "\nQuantity of HSTs, and/or Fabric Width. Please try again. ");
                    verify = false;
                    proceed = false;
               if(proceed)
                    all codes/printouts/methods
               }     //end of if proceed
               }     //end of verify
          }     //end of if
           }     //end of try
        catch (Exception e ) {
                output.append("General Exception");
          finally {
                textArea1.setText(output.toString());
   }     //end of action performed(i hope i quoted that right)
Any ideas on how to resolve this? I know I could use a switch in a standard java, but not sure if that works with applet/try-catch.
Thanks again,
Kimberly

You need to use "else" clauses here.if(t1.length() == 0 || t2.length() == 0 || t3.length() == 0)
output.append("\nPlease complete the required fields and try again.");
} else {
if(size == 0 || numOfSquares == 0 || WOF == 0)
    output.append("\nYou have entered a null value for Square Size, " +
    "\nQuantity of HSTs, and/or Fabric Width. Please try again. ");
} else {
    // all codes/printouts/methods

Basic (try catch finally)

Try catch and finally were thing i recently neglected to use unless my ide made me, but i was just reading on how to use them and I have a question about something i couldn't find an answer for:
objects you declare in try statements e.g.:
try{
BufferedReader br=...;
are only available in the scope of that try statement. Is this bad programming style or would "br" be automatically destroyed after the try statement is exited?

Well, define "dispose". If there's some method on the object that you need to call to clean that object up, you'll have to declare the variable outside the try block and then call it:
Something it;
try {
it = SomethingFactory.createHeavyObject();
it.doSomething(); // may throw Horse exception
it.doSomethingElse();
} catch (Horse e) {
e.printStackTrace();
} finally {
it.releaseResources();
it = null; // only necessary if there will be a long time before "it" goes out of scope
// and even then maybe not if releaseResources() took care of the heavy stuff
}On the other hand, you should never have to do this:
Something it;
try {
it = new Something();
it.doSomething(); // may throw Horse exception
} catch (Horse e) {
e.printStackTrace();
} finally {
it = null;
}Instead you could just do:
try {
Something it = new Something();
it.doSomething(); // may throw Horse exception
} catch (Horse e) {
e.printStackTrace();

Try Catch Blocks

This may be too vague of a question but is it bad practice to use one large try catch block? In my mind it seems like it would produce "cleaner" code as far as programmer reading is concerned, but does it affect the program adversely?
try {
// code goes here
} catch (somekindofexception e){
// print exception e
} catch (anotherkindofexception e){
// print exception e
} // continue for all possible exceptions

bolivartech wrote:
I was mistaken it looks like the particular function I was thinking of throws 3 kinds of RuntimeExceptions, but the same idea applies right?
try {
} catch (RuntimeException e) {
System.err.println("Caught RuntimeException: " + e.getMessage());
Yes, you can do that if you want to handle all of them the same.
However, if you want to handle different exceptions differently, you'd catch those specific exceptions, rather than the parent exception type. This is a separate issue from whether you have one big try or lots of little trys.
NOTE HOWEVER THAT YOU SHOULD NOT CATCH RuntimeException OR ITS DESCENDANTS. RuntimeException indicates an error in your code. Catching it is usually pointless, because you can't recover from it, and trying to continue on will probably lead to corrupt results at best.

Try/catch code

I have a question concerning java try-catch blocks. Is there a way for java to catch multiple exceptions in one block? For e.g. by enclosing the try/catch block within a loop? Is this possible?
Thanks.
Liza

Thanks for your responses...that code i already know
however i found out since that java will only catch
one exception at a time, even if the try/catch block
of code is enclosed in a loop.That doesn't make any sense.
There is only ever one exception at a time. You might have to code to catch more than one type of exception, but only one is generated at a time.

Need HELP with finally() in nested try-catch

hi,
i am having trouble with deadlock and wondering if its due to an incorrect use of finally nested within multiple try catch blocks.
is the inner finally() required, will the outer one get executed, or will the two finally() statements get executed...??
the deadlock happens very infrequently to accurately test.
try {
     try {
     catch (InterruptedException e) {
          return;
catch {
finally {
     //will this be executed be executed by the inner throw statement
}or is an inner finally required
try {
     try {
     catch (InterruptedException e) {
          return;
     //this finally is NEW....is it needed!
     finally {
          //will this be executed. will both get executed
catch {
finally {
     //will this be executed also, or completely ignored if exception throw from inner try/catch
}

inner/outer, which one is executed first?
more info pls.I mean, really. How hard is it to find out for yourself?
public class TestFinally {
    public static void main(String[] args) {
        try {
            try {
                throw new RuntimeException("Whatever");
            } finally {
                System.out.println("Inner finally");
        } finally {
            System.out.println("Outer finally");
}I'll leave it to your imagination as to how to modify this class to confirm the answers to your original question.

Error when using try catch inside oledb command to run stored procedure

Hi,
i'm using the below command to run some jobs using OLEDB Command
exec sp_start_job @job_name =?
and it runs successfully
when i put this code inside try catch block as below , it generates error and don't accept it
begin try
exec sp_start_job @job_name =?
end try
begin catch
end catch
the error message is "Syntax error, PErmission vaiolation or other nonspecific error"
do you know is there any problem using TRY catch insdie OLEDB command ?
Thanks ,
Ahmed Salah

Hi Ahmed,
According to your description, if an error raised that fails the package, then you want the package to continue execute.
To achieve this requirement, we can use Integration Services (SSIS) Event Handlers that we can create custom event handlers for an OnError event when an error occurs to continue processing rest of the package. For more details, please refer
to the following blog:
http://visakhm.blogspot.in/2013/03/error-handling-in-ssis-loops.html
If there are any other questions, please feel free to ask.
Thanks,
Katherine Xiong
Katherine Xiong
TechNet Community Support

Try/catching errors occuring in synchronous event handlers

Hi,
I know that using try/catch in flash player it is possible to catch only synchronous errors, but recently I ran into code in our application which I strongly believe is synchronous but it behaves as if it wasn't.
In example below I create event listener and inside try/catch I dispatch event. Handler function throws error. Executing code stops when error is thrown, so message "after throwing error" won't be logged, but try/catch block catches nothing and code executes as if nothing happened after event dispatch.
Dispatching event on element executes handler method immediately so it is synchronous execution. Event call stack which is displayed in debug versions of flash player, shows every function from creation of class to execution of handler.
Generally flash applications relays heavily on events and in my case it caused ours users projects to be irreversibly corrupted, because of this continuing to work after error, which I even can't properly detect and handle, cause it's going throught 5 or more event handlers and adding try/catch to each handler would create enormous chaos in my code. So my question is why does flash player behaves like this? Are there any ways to tell compiled SWF file to treat such cases as synchronous calls, f.e. compilation parameters?
package
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.EventDispatcher;
    import flash.text.TextField;
    public class TestApp extends Sprite
        public var cTextField:TextField;
        public function TestApp()
            cTextField = new TextField();
            cTextField.width = 300;
            cTextField.height = 200;
            addChild(cTextField);
            onAppCreated();
        protected function onAppCreated():void
            var eventName:String = "my_event";
            var caughtError:Boolean = false;
            var dispatcher:EventDispatcher = new EventDispatcher();
            dispatcher.addEventListener(eventName, handler);
            try
                dispatcher.dispatchEvent(new Event(eventName));
            } catch (error:Error)
                caughtError = true;
            cTextField.text += caughtError ? "caught error\n" : "error wasn't caught\n";
        protected function handler(event:Event):void
            cTextField.text += "before throwing error\n";
            throw new Error("throw error");
            cTextField.text += "after throwing error\n";

Okay, nobody bit. Sorry.
The only way to really figure out what is going on is to look at a running example with a C++ debugger. I'm particularly curious about whether this problem happens in a specific browser/os combination (we may be working around a quirk of that platform), or if it's something that happens everywhere.
The most effective way to proceed is going to be to file a bug with a simplified, executable example (source and compiled SWF, ideally) that demonstrates the problem. This will help me route the bug to a developer and get you an answer in the shortest time possible.
You can file a bug here:
http://bugbase.adobe.com/
If you reply here with the bug number, I'll get it assigned to an engineer.
Thanks!

PowerShell - Remote Sessions, Try{}Catch{}, ErrorActionPreference

Hello everyone,
I am encountering issues with Remote Exchange sessions and was wondering what I am overlooking/over-complicating.
I am running Windows 8.1/PowerShell 4.0. Reason I mention this is because of this blog post:
http://blogs.msdn.com/b/powershell/archive/2013/10/25/windows-management-framework-4-0-is-now-available.aspx
The IMPORTANT section noted that Exchange 2007, 2010, 2013 are not compatible with WMF 4.0 and didn't know if that is good/bad since the OS is using PowerShell 4.0.
1 - I am connecting to Office 365 utilizing the following:
http://help.outlook.com/en-us/140/cc952755.aspx
2 - I have the following function:
function Get-SomeMailboxStatistics {
[CmdletBinding()]
param(
[Parameter(Mandatory=$True,
ValueFromPipeline=$True,
HelpMessage="Identities or aliases to gather Exchange Statistics from.")]
[Alias('Username')]
[string[]]$Identity,
[string]$ErrorLog = 'C:\MbxStatsErrorLog.txt',
[switch]$LogErrors
BEGIN{}
PROCESS{
Write-Verbose "Beginning..."
foreach ($alias in $Identity)
Write-Verbose "Gathering info for $alias."
#trap [ManagementObjectNotFoundException] {$everythingOK = $false}
Try{
# $ErrorActionPreference = "Stop" # Testing purposes.
$everythingOK = $true
$gms = Get-MailboxStatistics -Identity $alias -ErrorAction Stop # http://technet.microsoft.com/library/hh847884.aspx
# Trap {
# throw $_
Catch{
$everythingOK = $false
Write-Warning "Lookup on $alias failed."
if ($LogErrors -eq $true){
$alias | Out-File $ErrorLog -Append
Write-Warning "Logged $alias to $ErrorLog."
if ($everythingOK){
$props = @{};
$props = @{'Alias' = $alias;
'DisplayName' = $gms.DisplayName;
'TotalItemSizeInBytes' = ($gms.TotalItemSize.Value.ToString() -replace "(.*$)|,| [a-z]*$", "");
'TotalDeletedItemSizeInBytes' = ($gms.TotalDeletedItemSize.Value.ToString() -replace "(.*$)|,| [a-z]*$", "");
'MailboxType' = $gms.MailboxType; };
$obj = New-Object -TypeName PSObject -Property $props
Write-Output $obj
END{}
Example: Get-SomeMailboxStatistics -Identity GoodAlias1,GoodAlias2,FailAlias,GoodAlias3 -LogErrors -ErrorLog 'C:\Logs\MbxStatsErrors.txt' -Verbose
The pipeline terminates on FailAlias, and then throws an error when it tries to pass the FailAlias to the $props.
$gms | Get-Member on a good alias is:
TypeName: Deserialized.Microsoft.Exchange.Management.MapiTasks.Presentation.MailboxStatistics
I have tried setting $ErrorActionPreference = 'Stop' in various sections and think I am scope-creeping/not catching the Error where I should be or PowerShell is flat-out ignoring something.
I have tried additional nested if{}else{} in the Try{}Catch{} and cannot get it to behave as expected.
I have also tried to Trap{[ManagementObjectNotFoundException]} and Throw exception in various portions without success.
However, setting $ErrorActionPreference = 'Stop' in the session window (from default of 'Continue') the script behaves as I expected it to, when encountering a non-existant mailbox, it logs the error. It doesn't seem to have issues executing on Windows 8.0/PowerShell
3.0.
I have encountered numerous blog/forum posts with no definitive answer/resolution.
Based some of my tests around some suggestions from this thread:
http://stackoverflow.com/questions/1142211/try-catch-does-not-seem-to-have-an-effect
Extras:
http://blogs.technet.com/b/heyscriptingguy/archive/2010/03/09/hey-scripting-guy-march-9-2010.aspxhttp://stackoverflow.com/questions/19553278/powershell-catch-non-terminating-errors-with-silentlycontinue
http://stackoverflow.com/questions/15545429/erroractionpreference-and-erroraction-silentlycontinue-for-get-pssessionconfigur
http://social.technet.microsoft.com/Forums/scriptcenter/en-US/228a3329-f564-4daa-ad70-6d869b912246/non-terminating-error-turned-into-a-terminating-error?forum=winserverpowershell

This is not the only problem with WMF 4.0
When you use -ErrorAction 'SilentlyContinue', $Error object is not set.
[PS]
$Error.Clear()
[PS]
$objContact =
Get-Contact -Identity
'CN=unknown contact,OU=Users,DC=mydomain,DC=mytopdomain'
-ErrorAction 'Stop'
The operation couldn't be performed because object 'mytopdomain.mydomain/Users/unknown contact' couldn't be found on 'mydc.mydomain.mytopdomain'.
+ CategoryInfo : NotSpecified: (:) [Get-Contact], ManagementObjectNotFoundException
+ FullyQualifiedErrorId : 482E7079,Microsoft.Exchange.Management.RecipientTasks.GetContact
+ PSComputerName : myexchange.mydomain.mytopdomain
[PS]
$Error.Count
1
[PS]
$Error.Clear()
[PS]
$objContact =
Get-Contact -Identity
'CN=unknown contact,OU=Users,DC=mydomain,DC=mytopdomain'
-ErrorAction 'SilentlyContinue'
[PS]
$Error.Count
0
That's why since Exchange 2010 SP3 Rollup 5 (i suppose when reading Exchange Supportability Matrix), The Exchange Management Shell link has been updated to use Powershell 2.0
Before 2010 SP3 Rollup 5
C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -noexit -command ". 'C:\Program Files\Microsoft\Exchange Server\V14\bin\RemoteExchange.ps1'; Connect-ExchangeServer -auto"
After 2010 SP3 Rollup 5
C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -version 2.0 -noexit -command ". 'C:\Program Files\Microsoft\Exchange Server\V14\bin\RemoteExchange.ps1'; Connect-ExchangeServer -auto"

Try - catch question..

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