Set vs Map for lookup code example

Example 1: maptoint vs map

Stream stream = Stream.of(1, 2, 3); //Will compile fine
IntStream intStream = IntStream.of(4, 5, 6); //Will compile fine

Stream s = IntStream.of(4, 5, 6); //Does not compile
Stream s = IntStream.of(4, 5, 6).mapToObj(e -> e); //mapToObj method is needed
IntStream is = Stream.of(4, 5, 6).mapToInt(e -> e); //mapToInt method is needed

Example 2: list vs set vs map

LIST: Can store duplicate values,
      Keeps the insertion order. 
      It allows multiple null values, 
      Also we can read a certain value by index.
- ArrayList not syncronized, array based class 
- LinkedList not synchronized, doubly linked
- Vector is synchronized, thread safe

SET: Can only store unique values, 
     And does not maintain order
- HashSet can have null, order is not guaranteed
- LinkedHashSet can have null and keeps the order 
- TreeSet sorts the order and don't accept null 

QUQUE : Accepts duplicates, 
        Doesn't have index num,
        First in first our order.  
       
MAP : is a (key-value format) 
      and keys are always unique, 
      and value can be duplicated. 
- HashTable don't have null key, sychronized(thread-safe)
- LinkedHashMap can have null key, keeps order
- HasHMap can have null key, order is not guaranteed
- TreeMap doesn't have null key and keys are sorted