Create an array of HashMaps while specifying HashMap<String, Integer>

Question

I am trying to create an array of HashMaps within a class and then retrieve a hashmap from the array for calculation purposes. Here is my code:

HashMap<String, Integer>[] boardPopulation= (HashMap<String, Integer>[]) new HashMap[populationSize];
    for(int i=0; i < populationSize; i++){
        generateQueens();
        boardPopulation[i] = queenMap;
    }
    for(int i=0; i < populationSize; i++){
        queenMap = boardPopulation[i];
        printBoard();
    }

When I compile I get two issues:

Board.java uses unchecked or unsafe operations, recompile with -Xlint:unchecked.
When I compile with "Xlint:unchecked" I get

Warning: [unchecked] unchecked cast HashMap[] boardPop.......(same as line 1 of above code)

required: HashMap[] found: HashMap[]

Please help me ! :D

Ideally I would like to not have to use Xlint unchecked, but ultimately I really just need to be able to retrive a HashMap from the list and assign it to queenMap so I can do calculations within the class.

Thankyou

Try @SuppressWarnings("unchecked") before your declaration of boardPopulation — Stefan Warminski
– Stefan Warminski, Commented Apr 3, 2017 at 6:13
Marking as duplicate. Answer is here: stackoverflow.com/a/14917529/2390219 — kukis
– kukis, Commented Apr 3, 2017 at 6:19
Possible duplicate of "Cannot create generic array of .." - how to create an Array of Map<String, Object>? — kukis
– kukis, Commented Apr 3, 2017 at 6:19

muzzlator · Accepted Answer · 2017-04-03 06:21:23Z

2

Sorry for answering a slightly different question but if an array isn't essential, have you tried using a generic list:

List<Map<String, Integer>> boardPopulations = new ArrayList<>();
boardPopulations.add(new HashMap<>());

answered Apr 3, 2017 at 6:21

muzzlator

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4 Comments

Dylan Atkinson Over a year ago

I literally just found something very similar and I think it is doing what I need now. Code: < List<Map<String, Integer>> boardPopulation = new ArrayList<Map<String, Integer>>(); for(int i=0; i < populationSize; i++){ generateQueens(); boardPopulation.add(i, queenMap);

muzzlator Over a year ago

Cool, looks better. If you're using java 7 I think should be able to just do List<Map<String, Integer>> boardPopulation = new ArrayList<>(), the type of the ArrayList<T> constructor should be inferred from the declaration of boardPopulation as a List<Map<String, Integer>>

Dylan Atkinson Over a year ago

Using Java 8. I now have a new issue. Is there any chance I could ask you to private chat to go into more detail? I'm asking because the new issue is less related to this question and more related to understanding the problem I am solving.

muzzlator Over a year ago

Go ahead, I don't know how to start one but I assume you do

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