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I play with multitreading for SwingWorker by using Executor, and I'm there by mistake identified wrong elements from the Vector, looks like as this code pretty ignores that element in Vector doesn't exist

my question -> how to/is possible to catch this exception(s) some way

simple output 

run: Thread Status with Name :StartShedule, SwingWorker Status is STARTED Thread Status with Name :StartShedule, SwingWorker Status is DONE Thread Status with Name :StartShedule, SwingWorker Status is STARTED Thread Status with Name :StartShedule, SwingWorker Status is DONE Thread Status with Name :StartShedule, SwingWorker Status is STARTED Thread Status with Name :StartShedule, SwingWorker Status is DONE BUILD SUCCESSFUL (total time: 11 seconds)

by uncomment 

//changeTableValues1(); // un-comment for get ArrayIndexOutOfBoundsException

everything is correct, I get ArrayIndexOutOfBoundsException and output is 

run: Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 2 at java.util.Vector.get(Vector.java:694) at KondorExport.Util.Help.Table.TableWithExecutor.changeTableValues1(TableWithExecutor.java:70) at KondorExport.Util.Help.Table.TableWithExecutor.access$100(TableWithExecutor.java:18) at KondorExport.Util.Help.Table.TableWithExecutor$2.actionPerformed(TableWithExecutor.java:61) at javax.swing.Timer.fireActionPerformed(Timer.java:271) at javax.swing.Timer$DoPostEvent.run(Timer.java:201) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) Thread Status with Name :StartShedule, SwingWorker Status is STARTED Thread Status with Name :StartShedule, SwingWorker Status is DONE BUILD SUCCESSFUL (total time: 10 seconds)

from code 

import java.awt.BorderLayout; import java.awt.event.ActionEvent; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.util.List; import java.util.Vector; import java.util.concurrent.Executor; import java.util.concurrent.Executors; import javax.swing.*; import javax.swing.table.*; public class TableWithExecutor extends JFrame { private static final long serialVersionUID = 1L; private String[] columnNames = {"Narrative", "Description"}; private Object[][] data = {{"About", "About"}, {"Add", "Add"}}; private JTable table; private Executor executor = Executors.newCachedThreadPool(); private Timer timerRun; private int delay = 3000; private Vector<String> fwDeals; private Vector<String> fwDeals1; public TableWithExecutor() { DefaultTableModel model = new DefaultTableModel(data, columnNames); table = new JTable(model) { private static final long serialVersionUID = 1L; @Override public Class getColumnClass(int column) { return getValueAt(0, column).getClass(); } }; table.setPreferredScrollableViewportSize(table.getPreferredSize()); JScrollPane scrollPane = new JScrollPane(table); add(scrollPane, BorderLayout.CENTER); prepareStartShedule(); } private void prepareStartShedule() { timerRun = new javax.swing.Timer(delay, startCycle()); timerRun.setRepeats(true); timerRun.start(); } private Action startCycle() { return new AbstractAction("Start Shedule") { private static final long serialVersionUID = 1L; @Override public void actionPerformed(ActionEvent e) { executor.execute(new TableWithExecutor.MyTask("StartShedule")); //non on EDT //changeTableValues1(); // un-comment for get ArrayIndexOutOfBoundsException } }; } private void changeTableValues1() { fwDeals1 = new Vector<String>(); fwDeals1.add("First"); // ElementAt(0) fwDeals1.add("Second");// ElementAt(1) checkDealsInDb1(fwDeals1.get(1), fwDeals1.get(2)); } private void checkDealsInDb1(String Str, String Str1) { table.getModel().setValueAt(Str, 0, 1); table.getModel().setValueAt(Str1, 1, 1); } private void changeTableValues() { fwDeals = new Vector<String>(); fwDeals.add("First"); // ElementAt(0) fwDeals.add("Second");// ElementAt(1) checkDealsInDb(fwDeals.get(1), fwDeals.get(2)); } private void checkDealsInDb(String Str, String Str1) { table.getModel().setValueAt(Str, 0, 1); table.getModel().setValueAt(Str1, 1, 1); } public static void main(String[] args) { TableWithExecutor frame = new TableWithExecutor(); frame.setDefaultCloseOperation(EXIT_ON_CLOSE); frame.setLocation(150, 150); frame.pack(); frame.setVisible(true); } private class MyTask extends SwingWorker<Void, Integer> { private String str; private String namePr; MyTask(String str) { this.str = str; addPropertyChangeListener(new SwingWorkerCompletionWaiter(str, namePr)); } @Override protected Void doInBackground() throws Exception { if (str.equals("StartShedule")) { changeTableValues(); } return null; } @Override protected void process(List<Integer> progress) { } @Override protected void done() { if (str.equals("StartShedule")) { } } } private class SwingWorkerCompletionWaiter implements PropertyChangeListener { private String str; private String namePr; SwingWorkerCompletionWaiter(String str, String namePr) { this.str = str; this.namePr = namePr; } SwingWorkerCompletionWaiter(String namePr) { this.namePr = namePr; } @Override public void propertyChange(PropertyChangeEvent event) { if ("state".equals(event.getPropertyName()) && SwingWorker.StateValue.DONE == event.getNewValue()) { System.out.println("Thread Status with Name :" + str + ", SwingWorker Status is " + event.getNewValue()); } else if ("state".equals(event.getPropertyName()) && SwingWorker.StateValue.PENDING == event.getNewValue()) { System.out.println("Thread Status with Mame :" + str + ", SwingWorker Status is " + event.getNewValue()); } else if ("state".equals(event.getPropertyName()) && SwingWorker.StateValue.STARTED == event.getNewValue()) { System.out.println("Thread Status with Name :" + str + ", SwingWorker Status is " + event.getNewValue()); } else { System.out.println("SomeThing Wrong happends with Thread Status with Name :" + str); } } } }

EDIT:

added re-thrown from Future#get() in done() method (by @takteek excellent suggestion) 

@Override protected void done() { if (str.equals("StartShedule")) { try { get(); //errLabel.setText(String.valueOf(get())); } catch (InterruptedException ie) { ie.printStackTrace(); } catch (ExecutionException ee) { ee.printStackTrace(); }catch (IllegalStateException is) { is.printStackTrace(); } } }

but output is still and only Got exception, would be so hard to get any exception(s) from this BlackBox 

run: Got exception Thread Status with Name :StartShedule, SwingWorker Status is STARTED Thread Status with Name :StartShedule, SwingWorker Status is DONE Got exception Thread Status with Name :StartShedule, SwingWorker Status is STARTED Thread Status with Name :StartShedule, SwingWorker Status is DONE Got exception Thread Status with Name :StartShedule, SwingWorker Status is STARTED Thread Status with Name :StartShedule, SwingWorker Status is DONE Got exception Thread Status with Name :StartShedule, SwingWorker Status is STARTED Thread Status with Name :StartShedule, SwingWorker Status is DONE BUILD SUCCESSFUL (total time: 13 seconds)
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2 Answers 2

Reset to default
14

I'm not sure it adds much, but I got the expected Caused by using the variation of takteek's answer shown below. I ran it from the command line to be sure the IDE wasn't "helping".

 $ java -cp build/classes TableWithExecutor StartShedule: PENDING -> STARTED java.util.concurrent.ExecutionException: java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 2 at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222) at java.util.concurrent.FutureTask.get(FutureTask.java:83) at javax.swing.SwingWorker.get(SwingWorker.java:582) at TableWithExecutor$MyTask.done(TableWithExecutor.java:103) at javax.swing.SwingWorker$5.run(SwingWorker.java:717) at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:814) at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:95) at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:824) at javax.swing.Timer.fireActionPerformed(Timer.java:291) at javax.swing.Timer$DoPostEvent.run(Timer.java:221) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:677) at java.awt.EventQueue.access$000(EventQueue.java:85) at java.awt.EventQueue$1.run(EventQueue.java:638) at java.awt.EventQueue$1.run(EventQueue.java:636) at java.security.AccessController.doPrivileged(Native Method) at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87) at java.awt.EventQueue.dispatchEvent(EventQueue.java:647) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) Caused by: java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 2 at java.util.Vector.get(Vector.java:694) at TableWithExecutor.changeTableValues(TableWithExecutor.java:64) at TableWithExecutor.access$100(TableWithExecutor.java:14) at TableWithExecutor$MyTask.doInBackground(TableWithExecutor.java:92) at TableWithExecutor$MyTask.doInBackground(TableWithExecutor.java:80) at javax.swing.SwingWorker$1.call(SwingWorker.java:277) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at javax.swing.SwingWorker.run(SwingWorker.java:316) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:680) StartShedule: STARTED -> DONE

Full code:

import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.event.ActionEvent; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.text.DateFormat; import java.util.Date; import java.util.List; import java.util.concurrent.Executor; import java.util.concurrent.Executors; import javax.swing.*; import javax.swing.table.*; /** @see https://stackoverflow.com/questions/7054627 */ public class TableWithExecutor extends JFrame { private static final int delay = 1000; private static final DateFormat df = DateFormat.getTimeInstance(); private String[] columnNames = {"Product", "Availability"}; private Object[][] data = {columnNames, columnNames, columnNames}; private DefaultTableModel model; private JTable table; private Executor executor = Executors.newCachedThreadPool(); private Timer timer; public TableWithExecutor() { model = new DefaultTableModel(data, columnNames); table = new JTable(model) { @Override public Class getColumnClass(int column) { return getValueAt(0, column).getClass(); } }; table.setDefaultRenderer(Date.class, new DefaultTableCellRenderer() { @Override protected void setValue(Object value) { setText((value == null) ? "" : df.format(value)); } }); table.setPreferredScrollableViewportSize(new Dimension(200, 100)); JScrollPane scrollPane = new JScrollPane(table); add(scrollPane, BorderLayout.CENTER); timer = new Timer(delay, startCycle()); timer.setRepeats(true); timer.start(); } private Action startCycle() { return new AbstractAction(MyTask.STARTSCHEDULE) { @Override public void actionPerformed(ActionEvent e) { executor.execute(new MyTask(MyTask.STARTSCHEDULE)); } }; } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { TableWithExecutor frame = new TableWithExecutor(); frame.setDefaultCloseOperation(EXIT_ON_CLOSE); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } private class MyTask extends SwingWorker<List<DateRecord>, DateRecord> { private static final String STARTSCHEDULE = "StartSchedule"; private String name = STARTSCHEDULE; MyTask(String name) { this.name = name; addPropertyChangeListener(new TaskListener(name)); } @Override protected List<DateRecord> doInBackground() throws Exception { for (int row = 0; row < model.getRowCount(); row++) { Date date = new Date(); date.setTime(date.getTime() + row * 1000); publish(new DateRecord(row, date)); } return null; } @Override protected void process(List<DateRecord> chunks) { for (DateRecord dr : chunks) { model.setValueAt(dr.date, dr.rowNumber, 1); } } @Override protected void done() { try { get(); } catch (Exception e) { e.printStackTrace(System.err); } } } private static class DateRecord { private int rowNumber; private Date date; public DateRecord(int recordNumber, Date date) { this.rowNumber = recordNumber; this.date = date; } } private static class TaskListener implements PropertyChangeListener { private String name; TaskListener(String name) { this.name = name; } @Override public void propertyChange(PropertyChangeEvent e) { System.out.println(name + ": " + e.getOldValue() + " -> " + e.getNewValue()); } } }
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4 Comments

there is about correctly naming proccess (most important) and then only to change protected Void doInBackground() throws Exception {...} to the standard try -> catch -> finally block, then by miracle works, thanks +1
@Eng.Fouad: I have to mention that this example was intended to display an error. Note that it (incorrectly) updated the GUI from doInBackground(). I've updated the code accordingly.
hmm .. you are accessing the model on the background thread, is that safe enough? (Wondering about that in my recent question :-)
@kleopatra: Good question. This works only because DefaultTableModel uses Vector, which is synchronized. A TableModel having some other internal data structure would have to make other arrangements.
11

I think the problem you're running into is that exceptions caught in the background thread are only re-thrown if you call get() when processing is complete. This seems to be a common problem with SwingWorker.

You can change your done() function to:

@Override protected void done() { if (str.equals("StartShedule")) { try { get(); } catch (Exception ex) { // This exception was thrown during processing ex.printStackTrace(); } } }

done() gets executed on the event dispatch thread so you can display any error messages you need to from there. I hope that helps some.

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4 Comments

thanks, that's right, but what/which of method return full printStackTrace(), because now I see only Got exception if exception(s) exists
hmmmm maybe I search on wrong places no idea how to get full printStackTrace(); btw +1
this is absolutely the thing you must ever do when you use SwingWorker. I think that the docs should hilight this fact better. An exception is considered a "final" result of a worker thread. This means that a SwingWorker<void, void> that doesn't return any object or value, should nevertheless been tested for a result with the get() method, which will reraise the exception arisen in the worker thread. Remember that exceptions go up the stack, but in a multi-threaded application there is a stack for each thread.
@AgostinoX thanks for comment, yes that would be half of true, in case of that you'll try example by (@trashgod) with remove throws exception and wrapping voids or classes inside try - catch bloks then Future returns exception(s), or if you can another issues with SwingWorker<void, void>, then don't hesitate and post that here as answer, because now I have some idea, (maybe with shadowed image) about fixies comings from Java1.6_021

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