How to keep the original sequence of a map

Question

I want the equivalent of a Hashtable or Map class (I need keys and corresponding objects) which, once fully populated, will guarantee to get the key/object pairs back out using the order in which they were added, rather than by sort order of the keys.
( The bigger objective is to compare two such collections, A and B, to see which key/object pairs exist in A but not B, and which exist in B but not A. However, for presentation purposes, I need to keep the original order in which everything was read.)
What's the most efficient way to do this ? I'm sure I've missed something really simplistic but, hey, it's Monday......

Answer 1

There is no way to retrieve objects from any map in the order they were incerted unless you add some logic to the way you are incering it.
Here is an example of such logic, where I want to retrieve "states" in the same order as I put them:
     public static void main(String[] args){
          HashMap map = new HashMap();
          map.put("1" + "PA", "Pensylvania");
          map.put("2" + "NJ", "New Jersey");
          map.put("3" + "CA", "California");
          map.put("4" + "TX", "Texas");
          LinkedList ls = new LinkedList(map.keySet());
          Collections.sort(ls);
          Iterator iter = ls.iterator();
         String stAbbrv = null;
          while (iter.hasNext()){
               stAbbrv = (String)iter.next();
               System.out.println(stAbbrv.substring(1) + " - " + map.get(stAbbrv));
     }the output is:
PA - Pensylvania
NJ - New Jersey
CA - California
TX - TexasHope it helps
Alex
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