I have a couple of questions about the code above.
1. Why line 4 gives compiler error, but line 3 does not. I notice a kind of similar between line 3 and line 4, see bold chars. Map<String, List<String> > map1 = new HashMap<String, List<String >>();
2. Map<String, List<String>> map1 = new HashMap<String, List<String>>(); How do I know List<String> is back by a an ArrayList, a LinkedList, or something else.
Thanks