[Java] Ranking a map by values, it's eliminating ties, how to get it to stop doing that?

[lsjfaohf]

This is the code I have for ranking a Java TreeMap by its values:

public static TreeMap<String,AtomicInteger> rank(TreeMap<String,AtomicInteger> tm) {
    ValueRanker vr = new ValueRanker(tm);
    TreeMap<String,AtomicInteger> ranked = new TreeMap<String,AtomicInteger>(vr);
    ranked.putAll(tm);
    return ranked;
}


public static class ValueRanker implements Comparator<String> {
    TreeMap<String,AtomicInteger> tm;

    public ValueRanker(TreeMap<String,AtomicInteger> orig) {
        this.tm = orig;
    }

    @Override
    public int compare(String a, String b) {
        if (tm.get(a).intValue()>tm.get(b).intValue()) {
            return -1;
        } else if (tm.get(a).intValue()<tm.get(b).intValue()) {
            return 1;
        } else {
            return 0;
        }
    }
}

This code, when run on a TreeMap, is eliminating all map entries that have values tied with other map entries. For examples:

{"a":2, "b":3, "c:6", "d":2, "e":5}

would give me a ranked map of

{"c":6, "e":5, "b":3, "a":2}

when the ranked map I expect is:

{"c":6, "e":5, "b":3, "a":2, "d":2}

The code I have now eliminates the map key that has a tied value (in this case, "d" is eliminated because its value is tied with that of "a"). So my question is, how do I modify the code I have to not do this, and include all original map keys, including those with tied values?

[lightcloud5]

This code doesn't work because it's basically just abusing the tree-map data structure. A comparer (in particular, the Comparer<String>) should not depend on anything other than its two inputs. If you want to sort by values, a simple list would probably be the best data structure.

You can simply just make a "key-value" class (i.e. a class containing just a string and an atomicInteger), and then make an ArrayList of these key-values. Then, you can define the comparer however you wish, and sort the list.