Java: How to convert List to Map

Question

Recently I have conversation with a colleague about what would be the optimal way to convert List to Map in Java and if there any specific benefits of doing so.

I want to know optimal conversion approach and would really appreciate if any one can guide me.

Is this good approach:

List<Object[]> results;

Map<Integer, String> resultsMap = new HashMap<Integer, String>();

for (Object[] o : results) {

    resultsMap.put((Integer) o[0], (String) o[1]);

}

Answer 1

List<Item> list;

Map<Key,Item> map = new HashMap<Key,Item>();

for (Item i : list) map.put(i.getKey(),i);

Understanding of course that each Item has a getKey() method that delivers a key of the proper type.