Map key or key in object?

[nimo frey]

What is better:

To use something like this:

private Map<String, MyObject> myObject= new HashMap<String, MyObject>();
// getter/setter

or is it better, to replace the String-Key of the Map as a property of MyObject, doing this, I can replace my Map to a List:

private List<MyObject> myObject= new ArrayList<MyObject>();
// getter/setter

What is better? When should I prefer the first one?

[nimo frey]

Oh, I guess I have to use the Map, as I cannot access a Object within the list directly.

In a map I can say:

myMap.get('mykey')

and it returns the corresponding object. If I put the key as a property in MyObject, then I cannot retrieve this object directyl:

myList.get(???).