HashMap and int as key

Question

I am trying to build a HashMap which will have integer as keys and objects as values.

My syntax is:

HashMap myMap = new HashMap&         


        

Answer 1

For somebody who is interested in a such map because you want to reduce footprint of autoboxing in Java of wrappers over primitives types, I would recommend to use Eclipse collections. Trove isn't supported any more, and I believe it is quite unreliable library (though it is quite popular anyway) and couldn't be compared with Eclipse collections.

import org.eclipse.collections.impl.map.mutable.primitive.IntObjectHashMap;

public class Check {
    public static void main(String[] args) {
        IntObjectHashMap map = new IntObjectHashMap();

        map.put(5,"It works");
        map.put(6,"without");
        map.put(7,"boxing!");

        System.out.println(map.get(5));
        System.out.println(map.get(6));
        System.out.println(map.get(7));
    }
}

In this example above IntObjectHashMap.

As you need int->object mapping, also consider usage of YourObjectType[] array or List<YourObjectType> and access values by index, as map is, by nature, an associative array with int type as index.

Answer 2

Please use HashMap<Integer, myObject> myMap = new HashMap<Integer, myObject>();

Answer 3

I don't understand why I should add a dimension (ie: making the int into an array) since I only need to store a digit as key.

An array is also an Object, so HashMap<int[], MyObject> is a valid construct that uses int arrays as keys.

Compiler doesn't know what you want or what you need, it just sees a language construct that is almost correct, and warns what's missing for it to be fully correct.

Answer 4

use int as Object not as primitive type

HashMap<Integer, myObject> myMap = new HashMap<Integer, myObject>();

Answer 5

You may try to use Trove http://trove.starlight-systems.com/
TIntObjectHashMap is probably what you are looking for.

Answer 6

If you code in Android, there is SparseArray, mapping integer to object.