public NSWindowController uniqueWindowControllerForClass(Class @class) { if (!(singleWindows != null)) singleWindows = NSMutableDictionary.dictionaryWithCapacity(5); NSWindowController w = singleWindows.objectForKey(@class); if (!(w != null)) { w = @class.alloc().init(); singleWindows.setObject(w) forKey(@class); } return w; }