Question

In my SWT Java app I often want to return information from inside a Display.syncExec() call. The best way I’ve found so far to do this is:

final ArrayList<Integer> result = new ArrayList<Integer>(); GUI.display().syncExec(new Runnable(){ public void run() {    MessageBox mb = /* ... */;     /* set up messagebox */    result.add(mb.open()); }}); if (SWT.OK == result.get(0)) { /* ... */ } 

I think this is allowed because ArrayList is thread-safe, but is there a better container I should be using, or an easier way altogether?

Answer 1

ArrayList is not thread-safe. You can obtain a thread-safe List with Collections.synchronizedList. However, it is much simpler to use an AtomicInteger in your case or AtomicReference in a more general case.

final AtomicInteger resultAtomicInteger = new AtomicInteger(); Display.getCurrent().syncExec(new Runnable() {      public void run() {         MessageBox mb = /* ... */;             /* set up messagebox */         resultAtomicInteger.set(mb.open()); }}); if (SWT.OK == resultAtomicInteger.get()) { /* ... */ }