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POWhy is my code not thread safe?
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copied!<p>I'm creating a game where levels can be loaded from a file. This is done on a separate thread, while everything else is done on the Event Dispatch Thread.</p> <p>I tested the code by loading from a really large test file, and it turns out that the Event Dispatch Thread on occasions is unresponsive while the level is being loaded.</p> <p>I can't seem to figure out the cause. Here's some of my code:</p> <pre><code>public class LevelSelectionWrapper extends GamePanel { ... private JList list; private File[] files; ... //Lock object for synchronization private Object lock = new Object(); //Runnable for loading levels from files on a separate thread private Runnable loader = new Runnable() { @Override public void run() { synchronized(lock) { //Load levels from files List<Level> levels = LevelLoader.load(files); // <------------- ... SwingUtilities.invokeLater(new ListUpdater()); } } }; ... private void createOpenFileButton(Container container) { final JFileChooser fc = ... ... //Create open button JButton openButton = new JButton("Open file"); openButton.setFocusable(false); openButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { int returnVal = fc.showOpenDialog(LevelSelectionWrapper.this); if(returnVal == JFileChooser.APPROVE_OPTION) { synchronized(lock) { files = fc.getSelectedFiles(); } //Load files on separate thread new Thread(loader).start(); // <------------- } } }); container.add(openButton); } } </code></pre> <p>I've added two arrows to the code:</p> <ul> <li>The first one is the time consuming method (when the files are really large). On occasions, the Event Dispatch Thread is unresponsive while this code is running.</li> <li>The last one is where the runnable is invoked.</li> </ul>

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