Java8 Imp stream Snippets:

(_grouping By):

1)  HashMap to Linked HashMap:

params.entrySet().stream()

.collect(Collectors.toMap(Map.Entry::getKey,Map.Entry::getValue,

        (e1,e2)->e2,LinkedHashMap::new));

2)Sum of HashMap Values:

  params.values().stream().mapToInt(Integer::valueOf).sum();

3)Grouping By:

   Map<Integer,List<String>> params=

users.stream().collect(Collectors.groupingBy(User::getId,

        Collectors.mapping(User::getName,Collectors.toList())));

 Map<Integer, EmployeeToMap> params=employees.stream()

.collect(Collectors.toMap(e-> e.getId(),

        Function.identity(),(o1, o2) -> o1, LinkedHashMap::new));

4)Summing Int:

   Map<Integer,Integer> params=

        users.stream().collect(Collectors.groupingBy(User::getId,
                Collectors.summingInt(e->1)));   

   Map<String,Integer> params = Stream.of(str.split(""))

.collect(Collectors.toList()).stream()

.collect(Collectors.groupingBy(String::valueOf,

        LinkedHashMap::new,Collectors.summingInt(e->1)));

(_flatmap):

User -> List<Address> = the Scenario we need to get only User details

 List<User> users1 = users.stream()

        .filter(employee -> employee.getAddresses().stream()
                .anyMatch(adr -> adr.getId().startsWith("1")))

        .collect(Collectors.toList());

List<Address> addresses1 =
        users.stream().map(User::getAddresses).flatMap(Collection::stream)

         .filter(ad -> ad.getId().equals("1")).collect(Collectors.toList());  

Finding Max & Min Value:

-> values.stream().max(Comparator.comparing(Integer::valueOf)).get()

-> values.stream().min(Comparator.comparing(Integer::valueOf)).get()

Sum of Values:

-> values.stream().mapToInt(Integer::intValue).sum()

Average Value:

values.stream().mapToInt(Integer::intValue).average().getAsDouble()