java.util.NoSuchElementException - on iterating over sorted treemap

Question

I'm looping over my program, and for no certain reasons I've got the following error

Exception in thread "main" java.util.NoSuchElementException
    at java.util.TreeMap$PrivateEntryIterator.nextEntry(Unknown Source)
    at java.util.TreeMap$KeyIterator.next(Unknown Source)
    at EloRating.setNewSeason(EloRating.java:242)

This error points to the iterator loop.

TreeMap<String,Double> treeMap = new TreeMap<String,Double>();
                                    for (Entry<String, Double> team : teamsIntersection.entrySet()) {
                                        treeMap.put(team.getKey(), listTeams.get(team.getKey()).getRating());
                                        }

                                    SortedSet<Entry<String, Double>> listSorted = entriesSortedByValues(treeMap);
                                    Iterator<Entry<String, Double>> iter = listSorted.iterator();

                                    int stop = (amountOfIntersectTeams+1)/2;
                                    for(int i = 0; i < (stop-1); i++){
                        ----------->   iter.next();
                                    }
                                    double median = iter.next().getValue();

If I execute the program once, nothing special happens. But for some benchmark reasons I've to loop over the program 25.000 times with some slightly adjusted parameters. And when I try to start the program again with the parameters from after an error, it will go further. [At the moment of this error, iterator contained 10 values]

Goal

I want to have the upper median on the values of the Hashmap teamsIntersection. e.g. a-3 b-1 c-2 d-2 e-5 f-4 then I want the value of 3 back from a

entriesSortedByValue

static <K,V extends Comparable<? super V>>
    SortedSet<Map.Entry<K,V>> entriesSortedByValues(Map<K,V> map) {
        SortedSet<Map.Entry<K,V>> sortedEntries = new TreeSet<Map.Entry<K,V>>(
            new Comparator<Map.Entry<K,V>>() {
                @Override public int compare(Map.Entry<K,V> e1, Map.Entry<K,V> e2) {
                    return e1.getValue().compareTo(e2.getValue());
                }
            }
        );
        sortedEntries.addAll(map.entrySet());
        return sortedEntries;
    }

Why don't you use the same convention (i.e. `for (Entry team : teamsIntersection.entrySet()) {...}`) to iterate over your collection set? — Mohammad Najar, Oct 10 '14 at 17:24
Because I want the median of that set. - I shall put some extra info on it — Dieter, Oct 10 '14 at 17:27
Similar question as in http://stackoverflow.com/questions/4191687/how-to-calculate-mean-median-mode-and-range-from-a-set-of-numbers — Mohammad Najar, Oct 10 '14 at 17:34
Where is the value of `amountOfIntersectTeams` set? Why not just use `listSorted.size()`? — sumitsu, Oct 10 '14 at 17:48
Sumitsu - it helped me well, by realising to changing my code so that i avoid the treemap by using a simple arrylist. — Dieter, Oct 10 '14 at 18:10

score 2 · Accepted Answer · answered Oct 10 '14 at 17:50

If you have multiple entries with the same value, they will get merged by the comparator you've written, since TreeSet dedups elements relative to its comparator.

Assuming that amountOfIntersectTeams is the size of the map you're dealing with, that's my best bet as to what's going on.

To fix it, I'd consider adding a secondary comparison of the keys in your Comparator when the values compare as equal.

java.util.NoSuchElementException - on iterating over sorted treemap

Goal

entriesSortedByValue

1 Answers1

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