java 8 list to map code example

Example 1: java map values to list

List<Value> list = new ArrayList<Value>(map.values());

Example 2: list to map of list java 8

Map<String,Set<String>> map =  list.stream().
           collect(Collectors.groupingBy(
                    Student::getName,
                    Collectors.mapping(e->getNum(e.getAddr()), Collectors.toSet())
                ));

   System.out.println("Map : "+map);