Java：如何将对象列表转换为字符串列表？

Question

I have a class named Pessoa

Classe Pessoa {
  Id Integer,
  Nome String
}

And in another part I have a list of objects of this class:

List<Pessoa> pessoas = getPessoas();

The above code works properly, but I need to transform it into a List<String> , where it only includes Nome field of class Pessoa .

How can I do that?

Answer 1

You can do it easily with Java 8 Streams :

List<String> names = pessoas.stream().map(Pessoa::getName).collect(Collectors.toList());

This is assuming your Pessoa class has a getName() method returning a String .

Answer 2

Assuming that the attribute Nome is public and "pessoas" is your list of Pessoa:

public List<String> getNomes(List<Pessoa> pessoasList) {
            List<String> nomes = new ArrayList<>();

            for(Pessoa pessoaObj : pessoasList){
                    nomes.add(pessoaObj.nome)
            }    

            return nomes;

}

If you didn't understand that for loop, I suggest for you to search a little about that loop syntax. It works very well for lists. Simple and easy.

Edit: As Eran said, it is easier using Streams, if using Java SDK 8 or newer :

List<String> names = pessoas.stream().map(Pessoa::getName).collect(Collectors.toList());

Or, using Kotlin:

val names = pessoas.map{it.name}