Question

I’m trying to find the differences between SwingWorker execute() vs doInBackground().So I have written this simple program to test the difference.

 public static void main(String[] args) {
    // TODO code application logic here
    for(int i=0;i<10;i++){
        try {
            new Worker().execute();
        } catch (Exception ex) {
            Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

public static class Worker extends SwingWorker<Void,Void>{

    @Override
    protected Void doInBackground() throws Exception {
       System.out.println("Hello");
       return null;
    }

}

When I run this program I got the following exception:

Exception in thread "AWT-Windows" java.lang.IllegalStateException: Shutdown in progress
    at java.lang.ApplicationShutdownHooks.add(ApplicationShutdownHooks.java:39)
    at java.lang.Runtime.addShutdownHook(Runtime.java:192)
    at sun.awt.windows.WToolkit.run(WToolkit.java:281)
    at java.lang.Thread.run(Thread.java:619)

However when I tried to use the doInBackground()

new Worker().doInBackground();

the program works and prints the expected result. So what is my error? and should I use the doInBackground() method as I have read that it shouldn’t be used.

Thanks

Answer 1

The execute() method is called on the current thread. It schedules SwingWorker for the execution on a worker thread and returns immediately. In your case, the main thread exits before scheduled worker thread has a chance to execute doInBackground() method. You can wait for the SwingWorker to complete using the get() methods.