How can I sort the keys of a Map in Java?

Question

This is a very basic question, I\'m just not that good with Java. I have a Map and I want to get a list or something of the keys in sorted order so I can iterate over them.

Answer 1

You have several options. Listed in order of preference:

1. Use a SortedMap:
   SortedMap myNewMap = new TreeMap(myOldMap);
   This is vastly preferable if you want to iterate more than once. It keeps the keys sorted so you don't have to sort them before iterating.
2. There is no #2.
3. There is no #3, either.
4. SortedSet keys = new TreeSet(myMap.keySet());
5. List keys = new ArrayList(myMap.keySet()); Collections.sort(keys);

The last two will get you what you want, but should only be used if you only want to iterate once and then forget the whole thing.