You can use
Map<String, List<String>> myMap = new HashMap<>();
instead of
Map<String, List<String>> myMap = new HashMap<String, List<String>>();
However, you can't use
List<String> list = new ArrayList<>();
list.add("A");
// The following statement should fail since addAll expects
// Collection<? extends String>
list.addAll(new ArrayList<>());
because it can't compile. Note that the diamond often works in method calls; however, it is suggested that you use the diamond primarily for variable declarations.