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 can use a list of the entry set rather than the key set and it is a more natural choice given you are sorting based on the value. This avoids a lot of unneeded lookups in the sorting and printing of the entries.

Map map = ...
List> listOfEntries = new ArrayList>(map.entrySet());
Collections.sort(listOfEntries, new SortByValueComparator());
for(Map.Entry entry: listOfEntries)
   System.out.println(entry);

static class SortByValueComparator implements Comparator> {
   public int compareTo(Map.Entry e1, Map.Entry e2) {
       return e1.getValue().compateTo(e2.getValue());
   }
}