Question

I am trying to use priority queue to keep an ordered list of integers. in a simple exaple like this:

PriorityQueue<Integer> queue = new PriorityQueue<>();
queue.offer(3000);
queue.offer(1999);
queue.offer(999);
for(Integer i : queue)
    System.out.println(i);

This prints

999
3000
1999

This is not what I am expecting considering natural odering.

I simply want to iterate without removing or adding through the queue (which serves as a sorted list) WITH ordering. Can I still do that in a simple manner?

Answer 1

PriorityQueue is a collection optimized for finding the tail or head value quickly, using a partially ordered tree structure called heap (look it up on wikipedia). If you pop the elements, they will be ordered. If you want to iterate, use for example a SortedSet instead, which also stores the elements sorted.