Adding a SimpleEntry to a SortedMap

Question

I wanted to create a variable I can iterate and sort later containing a "Move" and a double value. I thought my best shot would be the SortedMap with an integer (I read I need some kind of comparator) and an Entry containing my actual data. I have this method

    public SortedMap<Integer, Entry<Move, Double>> listFishMoves(Field fishField) {
    ArrayList<Move> fishMoves = getFishMoves(fishField);
    SortedMap<Integer, SimpleEntry<Move, Double>> moveMap = new SortedMap<Integer, SimpleEntry<Move, Double>>();
    int i = 0;
    for (Move move : fishMoves) {
        double turnValue = getMoveValue(move);
        moveMap.put(i, new SimpleEntry(move, turnValue));
        i++;
    }
}

My Problem is that I get an error in line 3 when initializing the SortedMap (Cannot instantiate the type SortedMap>). I also get 2 warnings when adding the new SimpleEntry: 1. Type safety: The expression of type AbstractMap.SimpleEntry needs unchecked conversion to conform to AbstractMap.SimpleEntry 2. Description Resource Path Location Type Type safety: The expression of type AbstractMap.SimpleEntry needs unchecked conversion to conform to AbstractMap.SimpleEntry

I am totally new to Maps and would really appreciate your help!

See also: [*How to use SortedMap interface in Java?*](https://stackoverflow.com/q/7427758/642706) — Basil Bourque, Dec 02 '18 at 22:44

score 1 · Accepted Answer · edited Dec 02 '18 at 22:43

1

Interface versus Implementation

Your problem is that SortedMap is an interface - you cannot instantiate it. You need to select an implementation that suits your need.

For instance, you could use a TreeMap.

SortedMap<Integer, SimpleEntry<Move, Double>> moveMap = new TreeMap<>();

For the warning, change your line to

moveMap.put(i, new SimpleEntry<>(move, turnValue));

Look for the words “interface”, “class”, and “implementing” when reading the JavaDoc.

edited Dec 02 '18 at 22:43

Basil Bourque

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answered Dec 02 '18 at 20:04

Ramsay Domloge

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looks like i missed that when reading the documentation, thank you! – NovaCaller Dec 02 '18 at 22:54

Adding a SimpleEntry to a SortedMap

1 Answers1

Interface versus Implementation