Throwing exceptions in an actionPerformed method

it tells me I can't do it
is there a way to get around this?
I'm reading a file inside the method so thats the exception in case it matters

It's not in swing.. i'm making it on eclipse
public void actionPerformed(ActionEvent e) {
read();
//do some stuff
private void read() throws Exception{
BufferedReader reader = new BufferedReader(new FileReader(file));
//read some stuff
thats the lines that are causing me trouble, the only thing i've learned to do is throw exceptions in read() though I know there are better ways such as try{ and catching specific exception I don't know how to use them.
when I try to make actionPerformed throw Exceptions like I did to read() it says:
Exception Exception is not compatible with throws clause in ActionListener.actionPerformed(Action Event)
So... I don't know what to do and this is the final step in a program i've been making for a while now.

Similar Messages

How to throw Exception in Thread.run() method

I want to throw exception in Thread.run() method. How can I do that ?
If I try to compile the Code given below, it does not allow me to compile :
public class ThreadTest {
     public static void main(String[] args) {
     ThreadTest.DyingThread t = new DyingThread();
     t.start();
     static class DyingThread extends Thread {
     public void run() {
     try {
               //some code that may throw some exception here
          } catch (Exception e) {
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}

(a) in JDK 1.4+, wrap your exception in RuntimeException:
catch (Exception e)
throw new RuntimeException(e);
[this exception will be caught by ThreadGroup.uncaughtException() of this thread's parent thread group]
In earlier JDKs, use your own wrapping unchecked exception class.
(b) if you know what you are doing, you can make any Java method throw any exception using Thread.stop(Throwable) regardless of what it declares in its "throws" declaration.

Throws Exception - a newcomer...

I have written a small amount of code that takes information from a text file and displays it in a GUI (swing) - this is called my RasterDisplay class. However, I am now creating another part of the GUI which will have a button that makes a new RasterDisplay. However, when I try and call my RasterDisplay constructor from within my actionPerformed method (see below) It tells me I have an "unhandled Exception type Exception". I can't throw Exception in the actionPerformed method so how do I get this method to work? Any help would be greatly appreciated - I am a total newcomer to Java and can't make head nor tail of related topics in all the forums...
Cheers!
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;
public class RasterToolbar extends JFrame implements ActionListener{
     JButton open;
     public static void main(String[] args) throws Exception{
          new RasterToolbar();
     //method to make display panel with buttons
     public RasterToolbar()throws Exception{
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               setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
               Container contentPane = getContentPane();
               JPanel p1 = new JPanel();
               p1.setLayout(new FlowLayout());
               p1.setBorder(BorderFactory.createEmptyBorder(4,4,4,4));
               open = new JButton("Open Viewer");
               p1.add(open);
               contentPane.add(p1,BorderLayout.WEST);
               open.addActionListener(this);
               pack();
               setVisible(true);
     public void actionPerformed(ActionEvent ev){
     if(ev.getSource()== open){
          System.out.println("Open pressed");
          RasterDisplay viewer = new RasterDisplay(); // HERE IS THE PROBLEM LINE!
}

public void actionPerformed(ActionEvent ev){
     if(ev.getSource()== open){
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How does it work : String MethdName (argument) throws Exception {}

HI,
I am very new to Java. I was looking through some code written by some other developer.
the code looks like
String MethdName (argument) throws Exception {
// some code here
What it exactly means? Are we forcing this method to always throw an exception? or only if some exception occurs then it will throw the exception?
Regards,
Lucky

It doesnt throw exceptions always.
What this means is that if you code inside the method does use some API or function that throws exceptions when a particular condition is not met, you method would throw the same exception to it's caller. If you didn't add the throw exception clause in your method, you would have to try/catch the exception that would be thrown in your code.
Or else, your code won't compile.
Summary:
A method that throws an uncaught, checked exception must include a throws clause in its declaration.
Read this for some additional info:
[Java Exception Handling|http://ajaxweb.wikidot.com/java-exception-handling]
[Sun Java Tutorial - Exceptions|http://java.sun.com/docs/books/tutorial/essential/exceptions/index.html]

How to throw exception in run() method of Runnable?

Hi, everyone:
I want to know how to throw exception in run() method of interface Runnable. Since there is no throwable exception declared in run() method of interface Runnable in Java API specification.
Thanks in advance,
George

Thanks, jfbriere.
I must add though that if your run() methodis
executed after a call to Thread.start(), then
it is not a good choice to throw anyRuntimeException
from the run() method.
The reason is that the thrown exception won't be
handled appropriately by a try-catch block.Why do you say that "the thrown exception won't be
handled appropriately by a try-catch block"? Can you
explain it in more detail?
regards,
George
Because the other thread runs concurrently with and independently of the parent thread, there's no way you can write a try/catch that will handle the new thread's exception: try {
myThread.start();
catch (TheExceptionYouWantToThrowFromRun exc) {
handle it
do the next thing This won't work because the parent thread just continues on after myThread.start(). Start() doesn't throw the exception--run() does. And our parent thread here has lost touch with the child thread--it just moves on to "do the next thing."
Now, you can do some exception handling with ThreadGroup and uncaughtException(), but make sure you understand why the above won't work, in case that was what you were planning to do.

Exporting methods that throw exceptions?

Using 10g Preview, I have encountered the following situation:
I've written a custom method in my ViewRowImpl class that I intend to export as a client row method. It's a public void method that takes a single String parameter.
Originally, I declared that the method throws Exception. With the throws clause present, the View Object wizard does not display the method in the list of available methods to export to the client. Removing the throws clause causes the method to appear in the list.
There's nothing in the documentation that I can find to explain this apparent restriction. The closest thing I can find has to do with all types in the signature being Serializable. Nothing is mentioned about exceptions.
Can somebody explain why methods that declare thrown exceptions can't be exported to the client? Or does the type of exception declared need to be narrower, such as a JboException?

I wondered the same thing. Take a look at this thread:
Why can't I throw exception from the Impl?

Exceptions - documentation on which methods throw exceptions ?

Hi, does anyone know where I can find full documentation on iphone SDK methods
The iphone SDK documentation seems to be incomplete.
For instance, the discussion section of the SDK documentation for NSMutableArray addObject method doesn't mention anything about exceptions.
However, the method could throw an exception (and this is mentioned in http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSMu tableArray_Class/Reference/Reference.html)
I'm assuming that alloc will not throw exceptions and that it will just return nil if no memory is available. However, I haven't found any documentation that states this.
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There is this
http://java.sun.com/products/jdbc/driverdevs.html
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In VS 2012 , ReportClass.Export(Exportoptions) throwing Exception "Method not found: 'CrystalDecisions.ReportAppServer.DataDefModel.PropertyBag CrystalDecisions.ReportAppServer.ReportDefModel.ISCRExportOptions.get_ExportOptionsEx()'".

Hi Team,
Problem : we are getting below exception on vs-2012 "Method not found: 'CrystalDecisions.ReportAppServer.DataDefModel.PropertyBag CrystalDecisions.ReportAppServer.ReportDefModel.ISCRExportOptions.get_ExportOptionsEx()'"
Could you please help me why we are getting this Error?
Note : Im not using Exportstream method , just using only Export method (refer code sample) for exporting Crystal report.
EnvironMent Details :
Crystal Report Version : CRforVS_13_0_5.exe
(SAP Crystal Reports runtime engine for >net Framework (64-bit)
SAP crystal Reports ,version for Microsoft Visual studio)
OS -Windows 7 -64 BIT
RAM : 16 GB
code where i Got the Exception
               dfdoFile.DiskFileName = Path.Combine(reportPath, reportFileName);
                expOptions.ExportDestinationType = ExportDestinationType.DiskFile;
                expOptions.ExportFormatType = ExportFormatType.CrystalReport;
                expOptions.DestinationOptions = dfdoFile;
                objReport.Export(expOptions);
below is stack trace :
   at CrystalDecisions.ReportSource.EromReportSourceBase.ExportToStream(ExportRequestContext reqContext)
   at CrystalDecisions.CrystalReports.Engine.FormatEngine.ExportToStream(ExportRequestContext reqContext)
   at CrystalDecisions.CrystalReports.Engine.FormatEngine.Export(ExportRequestContext reqContext)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.Export(ExportOptions options)
   at Medtech.BaseObjects.Report.CreatePDF(ReportClass objReport, DataView objRptDataView, String printerName, PrinterPaperOrientation
i have attached Screenshot for your reference ,

Hi Sandeep
You are using Service Pack 5 (Crystal Report Version : CRforVS_13_0_5.exe). I'd like you to update your install to SP 13:
SAP Crystal Reports, developer version for Microsoft Visual Studio: Updates & Runtime Downloads
and test.
- Ludek
Senior Support Engineer AGS Product Support, Global Support Center Canada
Follow me on Twitter

Programmatically adding chart to a report throws exception

programmatically adding chart to a report throws exception "chart condition fields are not valid".
Configuration:
I am using CR4E to create web application, I've added RAS jars (rasapp.jar, rascore.jar, reporttemplate.jar, serialization.jar) to this web application. For designing reports i am using Crystal Reports 2008.
Code:
<%
// Get the previously opened report from the session.
ReportClientDocument reportClientDocument =
     (ReportClientDocument)session.getAttribute("ReportClientDocument");
System.out.println(reportClientDocument.getReportDocument().getName());
// Try to get the report's DataDefinition object.
IDataDefinition dataDefinition;
try
     dataDefinition = reportClientDocument.getDataDefController().getDataDefinition();
// If the DataDefinition object can not be retrieved, redirect the user to an error page.
catch (Exception e)
     System.out.println("With error1");
    return;
// Create a new ChartDefinition object and set its type to ChartType.group.
ChartDefinition chartDefinition = new ChartDefinition();
chartDefinition.setChartType(ChartType.group);
Get the conditional field of the report's first group. Set this conditional
field for the ChartDefinition object using the setConditonalFields method. Notice
that the conditional field is first placed in a Fields collection because the
setConditionalFields method takes a Fields object as an argument.
Fields conditionFields = new Fields();
if (!dataDefinition.getGroups().isEmpty())
     IField field = dataDefinition.getGroups().getGroup(0).getConditionField();
     System.out.println("Condition field name ->" + field.getLongName(Locale.ENGLISH));
     conditionFields.addElement(field);
chartDefinition.setConditionFields(conditionFields);
//Get the summary field name from the form on the previous page.
String summaryFieldName = URLDecoder.decode(request.getParameter("summaryField"));
System.out.println("Summary field name ->" + summaryFieldName);
Loop through all of the report's summary fields until the one matching the name
above is found. Set this summary field for the ChartDefinition object using the
setDataFields method. Notice that the summary field is first placed in a Fields
collection because the setDataFields method takes a Fields object as an argument.
Fields dataFields = new Fields();
for (int i = 0; i < dataDefinition.getSummaryFields().size(); i++)
    IField summaryField = dataDefinition.getSummaryFields().getField(i);
     if (summaryField.getLongName(Locale.ENGLISH).equals(summaryFieldName))
          System.out.println("Adding data field ->" + summaryFieldName);
          dataFields.addElement(summaryField);
chartDefinition.setDataFields(dataFields);
Create a new ChartObject to represent the chart that will be added. Set the
ChartDefinition property of the ChartObject using the ChartDefinition object created
above.
ChartObject chartObject = new ChartObject();
chartObject.setChartDefinition(chartDefinition);
Get the chart type, chart placement, and chart title strings from the form on the
previous page. If no chart title was chosen, create a generic title.
String chartTypeString = request.getParameter("type");
String chartPlacementString = request.getParameter("placement");
String chartTitle = request.getParameter("title");
System.out.println("chartTypeString ->"+ chartTypeString + "<-chartPlacementString->" + chartPlacementString + "<-chartTitle->"+chartTitle);
if (chartTitle.equals(""))
     chartTitle = "untitled";
Create a ChartStyleType object and a AreaSectionKind object based on the
the chartTypeString and chartPlacementString retrieved above. In this example
possible chart types are bar chart and pie chart. Possible chart placements
are header and footer.
ChartStyleType chartStyleType = ChartStyleType.from_string(chartTypeString);
AreaSectionKind chartPlacement = AreaSectionKind.from_string(chartPlacementString);
// Set the chart type, chart placement, and chart title for the chart.
chartObject.getChartStyle().setType(chartStyleType);
chartObject.setChartReportArea(chartPlacement);
chartObject.getChartStyle().getTextOptions().setTitle(chartTitle);
// Set the width, height, and top for the chart.
chartObject.setHeight(5000);
chartObject.setWidth(5000);
chartObject.setTop(1000);
Get a ReportDefController object that can be used to modify the report's definition.
ReportDefController reportDefController;
try
     reportDefController = reportClientDocument.getReportDefController();
catch (Exception e)
     System.out.println("With Error2");
     return;
*Create a Section object that represents the section that will hold the chart.
If the chart placement was set header, get the header section, otherwise, if the
chart placement was set to footer, get the footer section.
Section chartSection = null;
if (chartPlacement.equals(AreaSectionKind.reportHeader))
     IArea reportHeaderArea =
          reportDefController.getReportDefinition().getReportHeaderArea();
     chartSection = (Section)reportHeaderArea.getSections().getSection(0);
else if (chartPlacement.equals(AreaSectionKind.reportFooter))
     IArea reportFooterArea =
          reportDefController.getReportDefinition().getReportFooterArea();
     chartSection = (Section)reportFooterArea.getSections().getSection(0);
Add the chart to the section using the ReportDefController object.
reportDefController.getReportObjectController().add(chartObject, chartSection, 1);
// Save the changes and close the report.
reportClientDocument.save();
reportClientDocument.close();
session.removeAttribute("ReportClientDocument");
%>
Trace:
com.crystaldecisions.sdk.occa.report.lib.ReportDefControllerException: The chart condition fields are not valid.---- Error code:-2147213287 Error code name:invalidChartObject
     at com.crystaldecisions.sdk.occa.report.lib.ReportDefControllerException.throwReportDefControllerException(Unknown Source)
     at com.crystaldecisions.sdk.occa.report.application.ReportObjectController.a(Unknown Source)
     at com.crystaldecisions.sdk.occa.report.application.ReportObjectController.a(Unknown Source)
     at com.crystaldecisions.sdk.occa.report.application.ReportObjectController.a(Unknown Source)
     at com.crystaldecisions.sdk.occa.report.application.ReportObjectController.a(Unknown Source)
     at com.crystaldecisions.sdk.occa.report.application.ReportObjectController.a(Unknown Source)
     at com.crystaldecisions.sdk.occa.report.application.ReportObjectController.add(Unknown Source)
     at org.apache.jsp.AddChart_jsp._jspService(AddChart_jsp.java:230)
     at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
     at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:387)
     at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
     at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:244)
     at java.security.AccessController.doPrivileged(Native Method)
     at javax.security.auth.Subject.doAsPrivileged(Subject.java:517)
     at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:276)
     at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:162)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:283)
     at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:56)
     at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:189)
     at java.security.AccessController.doPrivileged(Native Method)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:185)
     at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:244)
     at java.security.AccessController.doPrivileged(Native Method)
     at javax.security.auth.Subject.doAsPrivileged(Subject.java:517)
     at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:276)
     at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:218)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
     at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:56)
     at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:189)
     at java.security.AccessController.doPrivileged(Native Method)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:185)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
     at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179)
     at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
     at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156)
     at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:393)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:580)
     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
     at java.lang.Thread.run(Thread.java:595)

Please try this code snippet
var cs:ColumnSeries = new ColumnSeries();
cs.dataProvider = dp;
cs.displayName = "Series 2";
cs.yField = "values";
chart.series.push(cs);
OR
var temp:Array = [];
var cs:ColumnSeries = new ColumnSeries();
cs.dataProvider = dp;
cs.displayName = "Series 2";
cs.yField = "values";
temp = chart.series;
temp.add(cs);
chart.series = temp;

Question about throws exception in interface and realized class

Hi,all
If I define a method In the interface like that-
public void Execute() throws NumberFormatException; In the realized class, I can define this method like that-
public void Execute() throws RuntimeException{
System.out.println("test");
}This is a right realization. But if I manage it to throws Exception or to throws Throwable in the class it leads a error. Why add this restrict only to Exception? What is the purpose of this way?
Greetings and thanks,
Jason

When you say "throws NumberFormatException" you are really saying:
When using classes implementing this interface, you have to be prepared to deal with them throwing a NumberFormatException. Other exceptions won't happen.
When you come to implement it, it might not be possible for it to throw a NumberFormatException, so there's no reason why you should have to lie about that. Code handling it directly will be fine (it doesn't throw a NFE) and code handling it via the interface will be fine (it will handle NFEs, they just don't happen).
If your concrete implementation throws other sorts of exception, such as Exception or IOException, and so on, it's incompatible with code that's manipulating the interface. The interface says "NFEs might get thrown, nothing else will." while your implementation says "IOExceptions might get thrown".
So that explains why you can't use arbitrary exceptions. The special case is RuntimeException. RuntimeExceptions don't have to be caught, and it's expected that they can happen at any time - so there's no point trying to catch and handle them as a general case.
The classic example of a RuntimeException is a NullPointerException. You don't need to declare your method as throwing a NullPointerException even though it might get thrown. And you don't have to add NullPointerException to the throws part of the interface definition, because you already know that the concrete implementation could throw a NPE at any time.
Hope that helps (a little).
I'd recommend reading the API documentation on RuntimeException and Exception to get a clearer insight into this.
Dave.

Throws Exception

Dear Expert,
May I know how to throw Exception from a thread back to calling program ?
As I always get the following message when compiling the code
cannot override run() in java.lang.Thread; overridden method does not throw java.lang.Exception public void run() throws Exception
Thanks!
w

From what I can see in the javadoc, you can create a subclass of ThreadGroup and override its uncaughtException method, then you'd have to create a Thread that belongs to an instance of your ThreadGroup subclass and have its overridden method set some variable in your main thread. However you should recognize that whatever started your thread may not even exist when it throws that exception, and it may not be sitting around waiting for your thread to throw an exception. You should reconsider that requirement carefully before actually trying to implement it.

Dispatching GridSelectionEvent throw exception at runtime - A build issue with FB 4.5

This is a strang probelm I am facing with.
My code dispatches GridSelectionEvent after setting girds' selected item in one logic path. Following is code lines -
myDataGrid.selectedItem = instanceTag;
myDataGrid.dispatchEvent(new GridSelectionEvent(GridSelectionEvent.SELECTION_CHANGE));
Flash player throws following error on above statements encounter -
TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at spark.accessibility::DataGridAccImpl/eventHandler()
    at flash.events::EventDispatcher/dispatchEventFunction()
    at flash.events::EventDispatcher/dispatchEvent()
    at mx.core::UIComponent/dispatchEvent()
I am saying it is a strang for me because when I use swf file generated by Flex Builder (4.5)'s export to release build, it does not throw error and code works fine as expected.
But, when I user swf file generated by Ant script, I face the above issue.
The Flex builder settings is as shown in following image -
Ant mxmlc script is as follow -
<mxmlc
           file="${basedir}/src/AppMonConfigWizard.mxml"
            static-rsls="false"
           keep-generated-actionscript="false"
           output="${basedir}/bin-release/AppMonConfigWizard.swf" >
     <locale>en_US</locale>
      <load-config filename="${FLEX_HOME}/frameworks/flex-config.xml"/>
      <source-path path-element="${FLEX_HOME}/frameworks"/>
      <source-path path-element="${basedir}/src/locale/{locale}"></source-path>
      <compiler.library-path file="${basedir}/../wizard_framework/bin/wizard_framework.swc" append="true"/>
     <compiler.library-path file="${basedir}/../../utils/bin/utils.swc" append="true"/>
      <include-resource-bundles>ErrorMessages</include-resource-bundles>
      <include-resource-bundles>Strings</include-resource-bundles>
</mxmlc>
As mentioned earlier that following statements cause exception -
     myDataGrid.selectedItem = instanceTag;
     myDataGrid.dispatchEvent(new GridSelectionEvent(GridSelectionEvent.SELECTION_CHANGE));
If I change it to
     myDataGrid.setSelectedIndex(<some index value>)   /*selectedItem replaced with setSelectedIndex*/
     myDataGrid.dispatchEvent(new GridSelectionEvent(GridSelectionEvent.SELECTION_CHANGE));
it does not throw exception. I would like to mention that myDataGrid.selectedItem = instanceTag; does sets the selected item but then in that case issue arises when dispatching event.
I my application, similar statemetns were lot at many places (as there were no such issue with SDK 3.1 which was using earlier) so instead of making changes there, it would be better to imitate the build that Flex builder uses when exported the release build.
Thanks in advance,
Prithveesingh Zankat.

Solved it: had set the only public surface contracts checkbox by mistake and the cosntructor was protected...
Luis Abreu

Java Does Not Throw Exception When Writing To Read-Only Files

I have noticed that when I try to write to a read-only file in a window environment, Java does not throw an IOExcpetion, it just dosn't write to the file.
I am writing an FTP server and here is the code:
     public static long copyStream(InputStream in, OutputStream out)throws IOException
          IOException exception = null;
          long copied = 0;
          try
               byte buffer[] = new byte[1024];
               int read;
               while((read = in.read(buffer)) != -1)
                    out.write(buffer, 0, read);
                    copied += read;
          catch(IOException e)
               //ensures that the streams are closed.
               exception = e;
          try
               in.close();//ensures output stream gets closed, even if there is an
               //excption here.
          catch(IOException e){exception = e;}
          out.close();//try to close output.
          if(exception != null)
               //exception is not null, an exception has occured.
               //rethrow exception.
               throw exception;
          return copied;//all ok, return bytes copied.
     }Is this a bug in JAVA VM? Is so, how should I report it?

I have noticed that when I try to write to a read-only file in a window environment,
Java does not throw an IOExcpetion, it just dosn't write to the file.C:\source\java\Markov>attrib readonly.out
A R C:\source\java\Markov\readonly.out
�C:\source\java\Markov>java b
java.io.FileNotFoundException: readonly.out (Access is denied)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(Unknown Source)
at java.io.FileOutputStream.<init>(Unknown Source)
at b.main(b.java:5)
import java.io.*;
public class b {
    public static void main(String[] args) {
     try     {
          OutputStream os = new FileOutputStream ( "readonly.out");
     catch (Exception e) {
          e.printStackTrace();
}

Advanced Datagrid GroupingCollection of flat data (XMLLISTCollection) while sorting throws exception

HI,
     Iam using AdvancedDatagrid inorder to group the flat data populated from the backend through BlazeDS. Result data will be in xml format and i have converted it to xmllistcollection and assigned to the grouping collection source. Flat data is grouped by one of the attribute called 'Name' and refreshed after data has been populated.
Data structre used as input is: WIth this structure, iam grouping by the field 'Name'.
  <Report> <att_report>
<id>FDR1</id>
<Name>Feeder 1</Name>
<frequency>Monthly</frequency>
<Field>Finance 1</Field>
<Aug_10>100</Aug_10>
<Jul_10>200</Jul_10>
</att_report>
<att_report>
<id>FDR1</id>
<Name>Feeder 1</Name>
<frequency>Yearly</frequency>
<Field>Finance 2</Field>
<Jul_10>200</Jul_10>
</att_report>
<att_report>
<id>FDR2</id>
<Name>Feeder 2</Name>
<frequency>Quarterly</frequency>
<Field>Finance 3</Field>
<Jul_10>2000</Jul_10>
</att_report>
<att_report>
<id>FDR2</id>
<Name>Feeder 2</Name>
<frequency>MOnthly</frequency>
<Field>Finance 2</Field>
<Jul_10>2000</Jul_10>
</att_report>
<att_report>
<id>FDR4</id>
<Name>Feeder 4</Name>
<frequency>yearly</frequency>
<Field>Finance 5</Field>
<Jul_10>2000</Jul_10>
</att_report>
</Report>
Grouping is done as expected. We have additional functionalities like soring / seraching of the result set. Either one is working fine. Other functionality throws excpetion mentioned below.
When any of the advanced datagrid grid column header is clicked for sorting, it throws exception. I have pasted the exception below for reference.
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at mx.collections::HierarchicalCollectionView/internalRefresh()[C:\work\flex\dmv_automation\ projects\datavisualisation\src\mx\collections\HierarchicalCollectionView.as:709]
at mx.collections::HierarchicalCollectionView/refresh()[C:\work\flex\dmv_automation\projects \datavisualisation\src\mx\collections\HierarchicalCollectionView.as:686]
at mx.controls::AdvancedDataGridBaseEx/sortHandler()[C:\work\flex\dmv_automation\projects\da tavisualisation\src\mx\controls\AdvancedDataGridBaseEx.as:6869]
at mx.controls::AdvancedDataGrid/sortHandler()[C:\work\flex\dmv_automation\projects\datavisu alisation\src\mx\controls\AdvancedDataGrid.as:6899]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()
at mx.controls::AdvancedDataGrid/headerReleaseHandler()[C:\work\flex\dmv_automation\projects \datavisualisation\src\mx\controls\AdvancedDataGrid.as:7120]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()
at mx.controls::AdvancedDataGridBaseEx/mouseUpHandler()[C:\work\flex\dmv_automation\projects \datavisualisation\src\mx\controls\AdvancedDataGridBaseEx.as:5738]
at mx.controls::AdvancedDataGrid/mouseUpHandler()[C:\work\flex\dmv_automation\projects\datav isualisation\src\mx\controls\AdvancedDataGrid.as:8457]
I tried with couple of options but still not able to get rid of the excpetion. I browsed through couple of links also, still not able to find an solution. Can i know whether it is a bug or it can be fixed.
Any help / suggestions on this will be great.
Thanks in Advance,
Srinivasan

Read the error messages and pay attention to the line number of the error:
1)1 import java.io.*;
2
3 public class Test
4 {
5   public static void openFile()
6   {
7     FileOutputStream f = new FileOutputStream("data.txt");
8   }
9
10   public static void main (String[] args)
11   {
12     openFile();
13   }
14 }
$ javac -cp "" Test.java
Test.java:7: unreported exception java.io.FileNotFoundException; must be caught or declared to be thrown
    FileOutputStream f = new FileOutputStream("data.txt");
                         ^
1 error2)1 import java.io.*;
2
3 public class Test
4 {
5   public static void openFile() throws FileNotFoundException
6   {
7     FileOutputStream f = new FileOutputStream("data.txt");
8   }
9
10   public static void main (String[] args)
11   {
12     openFile();
13   }
14 }
$ javac -cp "" Test.java
Test.java:12: unreported exception java.io.FileNotFoundException; must be caught or declared to be thrown
    openFile();
            ^
1 error3)
1 import java.io.*;
2
3 public class Test
4 {
5   public static void openFile() throws FileNotFoundException
6   {
7     FileOutputStream f = new FileOutputStream("data.txt");
8   }
9
10   public static void main (String[] args)
11   {
12     try
13     {
14       openFile();
15     }
16     catch(FileNotFoundException e)
17     {
18       System.out.println("Error file doesn't exist.");
19     }
20   }
21 }
$ javac -cp "" Test.java
$
1 import java.io.*;
2
3 public class Test
4 {
5   public static void openFile() throws FileNotFoundException
6   {
7     FileOutputStream f = new FileOutputStream("data.txt");
8   }
9
10   public static void main (String[] args) throws FileNotFoundException
11   {
12     openFile();
13   }
14 }
$ javac -cp "" Test.java
$

Exception Handling in Overriden methods

class MyException extends Exception
MyException()
super("In MyException");
abstract class abs
abstract void show() throws ArithmeticException;
interface test
abstract void show() throws MyException;
abstract void get() throws Exception;
public class IntfOverride extends abs implements test
public void show() throws ArithmeticException
System.out.println("In overriden method show");
public void get()
System.out.println("In overriden method get");
public static void main(String[] args)
IntfOverride x=new IntfOverride();
x.show();
x.get();
In above i am not gettting any errors. why? I have not handle the MyException in method show() of interface 'test' in class IntfOverride..
If i change the signature as public void show() throws MyException then i am getting the error indicating ....why?
Thank u for ur answers....

Hi.....
I think when u change the signature public void show() throws MyException....then it considers the show() method as Interface method.........where in Interface U have allready defined this method......
when u r implementing these methods in a class...I don't think u have to use complete signature........
U can even try with get() method....If u try to use complete signature u get error....

Throwing exceptions in an actionPerformed method

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