I think you only have to know situations when
you should use 'right' collection type.
just remember the Collection and Map interface hirachy. what are the concrete classes etc.
and characteristics of each collection type. like,
Set: only unique element. one null is allowed.
List: non-unique element.
Map: Key-value pairs. all keys must be unique and non-null.
Now there can be sorted/unsorted, ordered/unordered implementations of above interfaces.