How to copy an attribute from a list in java

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How to copy an attribute from a list in java

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#1 by (5 votes)

0

Sample Copy:

List<MyObject> listaDeObjetos = new ArrayList<>();

List<String> nomes = new ArrayList<>();
for (MyObject obj : listaDeObjetos) {
   nomes.add(obj.getNome());
}

Is there anything in java that makes this easy?

java

asked by anonymous 05.10.2015 / 23:46

1 answer

Change scenarios with loop Loop to calculate the maximum value

score 5 · Accepted Answer

In Java 8 you can do this by using streams : / p>

List<MyObject> listaDeObjetos = new ArrayList<>();

List<String> nomes = listaDeObjetos.stream().map(MyObject::getNome)
                     .collect(Collectors.toList());

I do not know what exact type of the list this Collectors.toList() is returning. If you really need to be ArrayList , you can replace it with toCollection :

                     .collect(Collectors.toCollection(ArrayList::new));

Finally, if your list is too large maybe compensate replace stream() with parallelStream() , so Java can distribute multi-core processing (in this case simple do not make up).

I do not know anything about Java 7 or earlier that might make it easier, but the simplest thing is to do a loop, just like you already do. By the way, in the "performance" question I believe (but have not tested) that your loop is faster than the use of streams, and in that case, one is as concise as the other.