Can't initialize queue

Question

I need to sort an array of File and then copy it into a queue, I need this queue to be global.
Let queue be _sortedDateQueue.
How can I do this, here is the method of my class which uses it:
public Queue sortArrayByDate(File[] allfiles)
          Arrays.sort(allfiles, new Comparator()
               public int compare(Object o1, Object o2) {
               File f1 = (File)o1;
               File f2 = (File)o2;
               return ((Long.valueOf(f1.lastModified())).compareTo(Long.valueOf(f2.lastModified())));
for(int i=0; i < allfiles.length ; i++)
               _sortedDateQueue.offer(allfiles); // I am getting null ointer exception here
               System.out.println("Sorted Queue :" + _sortedDateQueue.peek());
          for (Iterator iter = _sortedDateQueue.iterator(); iter.hasNext();)
               File element = (File) iter.next();
               System.out.println("Sorted Queue :" + element.getName());
          return _sortedDateQueue;
How can I intialaize queue as its an interface?

Answer 1

you just create an object of some class that you prefer which implements Queue; for example, here I use LinkedList
Queue<File> _sortedDateQueue = new LinkedList<File>();also when you add to it you probably wanted
_sortedDateQueue.offer(allfiles);