panel.setDelegate(ocProxy.id());
int button = panel.runModalForTypes(null);
// or, eg
// NSArray.CLASS.arrayWithObjects(
// NSString.stringWithString("txt"), null));
NSString filenameAsNSString = panel.filename();
if (button == NSOpenPanel.NSOKButton) {
assertTrue(filenameAsNSString.toString().startsWith("/Users"));
} else {
assertEquals(NSOpenPanel.NSCancelButton, button);
assertNull(filenameAsNSString);