Create List of Object from Another Using Java 8 Streams

Create a list of objects from another list using Java 8 streams

You can do it with a custom collect(I added getters and some obvious constructors):

Map<String, OrganismeDTO> map = dt.stream().collect(HashMap::new, (m, t) -> {
    m.computeIfAbsent(t.getOrganismeLib(), x -> new OrganismeDTO(t.getOrganismeLib())).getRolesDTO().add(new RoleDTO(t.getRoleLib()));
}, (m1, m2) -> {
    m2.forEach((k,v) -> {
        OrganismeDTO organismeDTO = m1.get(k);
        if (organismeDTO != null ) {
            organismeDTO.getRolesDTO().addAll(v.getRolesDTO());
        } else {
            m1.put(k, v);
        }
    });
});

And then all that's left if to create List from the values.

List<OrganismeDTO> list = map.values().stream().collect(Collectors.toList());

Java : use Streams to convert List<Object> to another List<anotherObject>

You can use the Collectors.mapping along with groupingBy of samples(Sample instead of Object) to get an intermediate state of List<User> with the id they are associated to and them map each such entry to a ResultObject as:

List<ResultObject> resultObjects = samples.stream()
        .collect(Collectors.groupingBy(Sample::getId,
                Collectors.mapping(a -> new User(a.getUserName(), a.getAddress(), a.getEmail()),
                        Collectors.toList())))
        .entrySet().stream()
        .map(e -> new ResultObject(e.getKey(), e.getValue()))
        .collect(Collectors.toList());

Java 8 streams: getting lists of objects by property inside of an object in the object

It seems you want something like this:

List<User> result =  usersList.stream()
            .filter(user -> user.getBasket().getApplianceList().stream()
                 .anyMatch(appliance -> 
                          appliance.getApplianceName().equals("something1")))
            .collect(Collectors.toList());

How to convert list of object to another list object using streams?

Simple use map() method in stream api and collect results:

  List<Emp> employe = Arrays.asList(new Emp(1, 100), new Emp(2, 200), new Emp(3, 300));
  List<Emp> employeRise = employe.stream()
                                 .map(emp -> new Emp(emp.getId(), emp.getSalary * 100))
                                 .collect(Collectors.toList());
  employeRise.stream()
            .forEach(s -> System.out.println("Id :" + s.getId() + " Salary :" + s.getSalary()));

Fetch List of object from another list using java 8

Stream the contents, map to get the state and collect it as a List.

customers.stream()
    .map(Customer::getState)
    .collect(Collectors.toList());

If you need an ArrayList as the resultant list

customers.stream()
    .map(Customer::getState)
    .collect(Collectors.toCollection(ArrayList::new));

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