Question

I have a function that executes when a button is clicked. Suppose there is a loop to add 1 to 10 to a JList. I add that data to DefaultListModel. It works perfectly and the numbers get added. Then I added a Thread.sleep(1000) within the loop. But the output is different. I wanted to add 1 element every second. But now it waits for 10secs and the add all 1 to 10 together at the end of 10th second. Am I wrong anywhere?

List processList = listNumbers.getSelectedValuesList();
DefaultListModel resultList = new DefaultListModel();
listResult.setModel(resultList);

for (int i = 0; i < processList.size(); i++) {
    resultList.addElement(String.valueOf(i));
    try {
        Thread.sleep(1000);
    }
    catch (InterruptedException ex) {
    }
}

Answer 1

You should update your list in a separate thread otherwise you end up blocking the event dispatch thread.

Try the following:

final DefaultListModel model = new DefaultListModel();
final JList list = new JList(model);

//another thread to update the model
final Thread updater = new Thread() {
    /* (non-Javadoc)
     * @see java.lang.Thread#run()
     */
    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            model.addElement(i);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
    }
};
updater.start();