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Set<Integer> keys = map.keySet();
int[] array = new int[keys.size()];
int index = 0;
for(Integer element : keys) array[index++] = element.intValue();
for(int i : array) System.out.println(i);
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let myMap = new Map().set('a', 1).set('b', 2);
let keys = Array.from( myMap.keys() );
// ["a", "b"]
//or
let keys =[ myMap.keys() ];
// ["a", "b"]