Java 8 lambda create list of Strings from list of objects

Question

I have the following qustion:

How can I convert the following code snipped to Java 8 lambda style?

List<String> tmpAdresses = new ArrayList<String>();
for (User user : users) {
    tmpAdresses.add(user.getAdress());
}

Have no idea and started with the following:

List<String> tmpAdresses = users.stream().map((User user) -> user.getAdress());

Solution 1

You need to collect your Stream into a List:

List<String> adresses = users.stream()
    .map(User::getAdress)
    .collect(Collectors.toList());

For more information on the different Collectors visit the documentation.

User::getAdress is just another form of writing (User user) -> user.getAdress() which could as well be written as user -> user.getAdress() (because the type User will be inferred by the compiler)

Solution 2

It is extended your idea:

List<String> tmpAdresses = users.stream().map(user ->user.getAdress())
.collect(Collectors.toList())

Solution 3

One more way of using lambda collectors like above answers

 List<String> tmpAdresses= users
                  .stream()
                  .collect(Collectors.mapping(User::getAddress, Collectors.toList()));

Comments

[Shubhendu Pramanik]

You should add a new answer if its better/ alternative than the other one. Explain how its better.

[Gaurav Khandelwal]

This was indeed helpful to get it from List<Map>, thanks.

[Lino]

This doesn't attempt to answer the OPs question, though. OP is explicitly asking to map a User to its adress. Also how is your question different to the already existing ones?