Sorting a HashMap based on Value then Key? [duplicate]

Question

Possible Duplicate:
How to sort a Map<Key, Value> on the values in Java?

I have a HashMap of the type:

HashMap<String, Integer> h = new HashMap<String, Integer>();

The HashMap contains a list of Strings and the Integer is a counter for the number of times that String has been found. What I would like to be able to do is sort the HashMap based on the Integers, then on the alphabetical order of the Strings.

At the moment I am keeping a record of the largest occurrence of a word (variable named max) and displaying the values as follows:

public void print(){
    while(max > 0){
       for (String key : h.keySet()){
           if(h.get(key) == max){
               System.out.println(key + " " + h.get(key));
           }
       }
       max--;
    }
}

Which doesn't sort the values alphabetically, also it accesses the HashMap max*h(size) times.

What is the better solution?

Answer 1

Here's a Comparator that sorts Map.Entry objects with Comparable keys and values:

public class ValueThenKeyComparator<K extends Comparable<? super K>,
                                    V extends Comparable<? super V>>
    implements Comparator<Map.Entry<K, V>> {

    public int compare(Map.Entry<K, V> a, Map.Entry<K, V> b) {
        int cmp1 = a.getValue().compareTo(b.getValue());
        if (cmp1 != 0) {
            return cmp1;
        } else {
            return a.getKey().compareTo(b.getKey());
        }
    }

}

You'd put all of the map entries into a list and then sort that:

List<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(h.entrySet());
Collections.sort(list, new ValueThenKeyComparator<String, Integer>());