How print out the contents of a HashMap in ascending order based on its values?

Question

I have this HashMap that I need to print out in ascending order according to the values contained in it (not the keys

Answer 1

You aren't going to be able to do this from the HashMap class alone.

I would take the Map codes, construct a reverse map of TreeMap reversedMap where you map the values of the codes Map to the keys (this would require your original Map to have a one-to-one mapping from key-to-value). Since the TreeMap provides Iterators which returns entries in ascending key order, this will give you the value/key combination of the first map in the order (sorted by values) you desire.

Map reversedMap = new TreeMap(codes);

//then you just access the reversedMap however you like...
for (Map.Entry entry : reversedMap.entrySet()) {
    System.out.println(entry.getKey() + ", " + entry.getValue());
}

There are several collections libraries (commons-collections, Google Collections, etc) which have similar bidirectional Map implementations.