Bagaimana untuk mendapatkan ArrayIndexOutOfBoundsException apabila menggunakan Executor dan SwingWorker untuk multi-threading
Soalan:
Saya menggunakan Executor untuk SwingWorker Saya menghadapi masalah dengan multithreading. Jika saya mengakses elemen daripada Vektor yang tidak wujud, kod tersebut seolah-olah mengabaikan elemen tersebut. Bagaimana untuk mendapatkan pengecualian ini?Jawapan:
Melempar semula pengecualian yang diperoleh daripada Future#get() dalam kaedah done() SwingWorker menjadikan pengecualian dalam soalan mungkin. Kaedah done() yang diubah suai kelihatan seperti ini:@Override protected void done() { try { get(); } catch (InterruptedException | ExecutionException | IllegalStateException e) { e.printStackTrace(); } }
Contoh kod penuh:
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 java.util.concurrent.Future; 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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