CODEWITHSUNDEEP
javafor-looplambdajava-8
user68883
user68883

Reputation: 838

Java 8 way of adding in custom elements to a collection?

Is there a java 8 way of doing the following?

for(int i;i<=100;i++){
    Person person=new Person();
    person.setId(i);
    person.setName("name"+i);
    list.add(person)
}

Upvotes: 3

Views: 219

Answers (2)

M A
M A

Reputation: 72844

Yes:

IntStream.rangeClosed(0, 100)
    .forEach(i -> {
       Person person=new Person();
       person.setId(i);
       person.setName("name"+i);
       list.add(person);
     });

EDIT:

As commented below, accessing an existing list inside the lambda expression parameter of the stream operation goes against functional programming. It's better to do:

List<Person> persons = IntStream.rangeClosed(0, 100)
    .mapToObj(i -> {
       Person person=new Person();
       person.setId(i);
       person.setName("name" + i);
       return person;
      })
      .collect(Collectors.toList());

See https://docs.oracle.com/javase/8/docs/api/java/util/stream/IntStream.html.

Upvotes: 4

Tunaki
Tunaki

Reputation: 137084

You can obtain a list of persons by mapping each int from 0 to 100 into a Person.

List<Person> persons = IntStream.rangeClosed(0, 100).mapToObj(i -> {
    Person person = new Person();
    person.setId(i);
    person.setName("name" + i);
    return person;
}).collect(Collectors.toList());

Then, you can append that persons list into an existing one for example.

IntStream.rangeClosed return a IntStream of primitive int. Each is mapped to the object Person with mapToObj and collected into a list with Collectors.toList().

It would be cleaner if you had a constructor of Person taking the id and the name. With such a constructor, you could write:

List<Person> persons = IntStream.rangeClosed(0, 100)
                                .mapToObj(i -> new Person(i, "name" + i))
                                .collect(Collectors.toList());

Upvotes: 7

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