java - Is the order of values retrieved from a HashMap the insertion order

Question

I am trying figure out the order in which the values in a HashMap are/can be retrieved. Heres the code snippet for the same.

import java.util.HashMap;

public class HashMapExample {

   public static void main(String[] args) {
       HashMap<Integer, String> hashmap = new HashMap<Integer, String>();
       hashmap.put(1, "apple" );
       hashmap.put(2, "lemon" );
       hashmap.put(3, "orange" );
       hashmap.put(4, "banana" );
       hashmap.put(5, "litchi" );
       hashmap.put(6, "mango" );
       hashmap.put(7, "papaya" );

       System.out.println(hashmap.size());

       for (String key : hashmap.values()) {
           System.out.println(key);
       }
   }
}

output:

7
apple
lemon
orange
banana
litchi
mango
papaya

The values are printed in the order in which they have been inserted. Is this true in general? I was expecting the values to be printed in an arbitrary order. This is using Java 6.

Answer 1

From the Javadoc: HashMap "class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time."

If you need consistent ordering, you can use LinkedHashMap (for insertion/access order), or TreeMap (for comparision order). Please note, that these maintain the order of the keys, not the values.