JAVA

convert list to map java

Map<String, Item> map = 
    list.stream().collect(Collectors.toMap(Item::getKey, item -> item));

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);

map list to hashmap java8

// convert List<Elem> into a Map<Elem::getName, Elem:getId>
Map<String, String> myMap = elemsList.stream()
  .collect(Collectors.toMap(elem -> elem.getName(), elem -> elem.getId()));
// you may pay attention of elem null cases