LinkedHashMap ordered by value

Question

I'm trying find a structure similar to a LinkedHashMap that sorts it by its value. I'll need to be able to update the values. I'll be checking the order very often, so I need a solution that avoids sorting the Map every time.

something like this:

DynamicSortedMap<String,Integer> map = new DynamicSortedMap<String,Integer>();
map.put("key1",4);
map.put("key2",3);
map.put("key3",6);
System.out.println("Map: "+map);
map.update("key1",1);
System.out.println("Update:"+map);

Output:

Map: {key3=6, key1=4, key2=3}
Update: {key3=6, key2=3, key1=1}

Is there any stucture that allows this? If not, any ideas of how to do it?

Thanks for your help,

A `LinkedHashMap` is ordered by insertion not value. What you're looking for is [`TreeMap`](http://docs.oracle.com/javase/6/docs/api/java/util/TreeMap.html). — Ian Bishop, Aug 14 '12 at 12:26
I echo the recommendation of TreeMap. What features of LinkedHashMap made you pick it over other Maps? — Paul Tomblin, Aug 14 '12 at 12:28
`TreeMap` is sorted by key (but I think OP wants it like that). :) — dacwe, Aug 14 '12 at 12:28
I need to be sorted by value, and to be able to update the different elements (if there is not other solution, I may remove and re-insert the element with the new value) — magodiez, Aug 14 '12 at 12:49

score 1 · Answer 1 · answered Aug 14 '12 at 12:28

1

I think you are looking for something like TreeMap, which is sorted by key:

SortedMap<String, Integer> map = new TreeMap<String, Integer>();

answered Aug 14 '12 at 12:28

Reimeus

158,255
15
216
276

score 0 · Answer 2 · answered Aug 14 '12 at 13:17

0

Even though LinkedHashMap in fact could be a good base for this it's unfortunately very limited in manipulating the iteration order. I think with apache common-collections your better on.

answered Aug 14 '12 at 13:17

Bernd Ebertz

1,317
8
10

score 0 · Answer 3 · answered Aug 14 '12 at 14:41

class SortValueMap extends HashMap<String,Integer>{

    @Override
    public Set<Entry<String,Integer>> entrySet() {
        List<Entry<String,Integer>> entries = new ArrayList<Entry<String,Integer>>(super.entrySet());
        Collections.sort(entries, new Comparator<Entry<String,Integer>>(){

            @Override
            public int compare(Map.Entry<String,Integer> o1, Map.Entry<String,Integer> o2) {
                return o1.getValue().compareTo(o2.getValue());
            }});
        return new LinkedHashSet<Entry<String,Integer>>(entries);
    }
 }
    ...
SortValueMap  map = new SortValueMap();
map.put("key1",4);
map.put("key2",3);
map.put("key3",6);
map.put("key4",1);
System.out.println("Map: "+map);

LinkedHashMap ordered by value

3 Answers3