Create object from list using stream/map java 8

Question

I have a list of objects. I would like to create individual objects from this list with a method and not calling always: personList.get(0), personList.get(1), etc. The object name should be the Person name from the list element.

List<Person> personList = ...;

I'd like to iterate over the personList and create new objects by name for each object from the list.

Person class contains name attribute with a getter.

How can I do that?

You want to return a list of Person where the persons object have only name! or what exactly? — Youcef LAIDANI
– Youcef LAIDANI, Commented Jun 27, 2018 at 18:44
your question is not very clear. Can you mention a sample list input and the sample expected output? What do you mean by "it works case by case"? what is not working in the above case? — gagan singh
– gagan singh, Commented Jun 27, 2018 at 19:04
I updated the description, and remove the misleading code. Hope it is clear now. Thanks! — arena
– arena, Commented Jun 27, 2018 at 19:56

Ousmane D. · Accepted Answer · 2018-06-27 19:59:17Z

7

Just stream the list and invoke the map operation as follows:

personList.stream()
          .map(x -> new T(x.getName()))
          .collect(Collectors.toList());

Where T is the new type of elements you want to create e.g. Student, Person, Employee etc..

answered Jun 27, 2018 at 19:59

Ousmane D.

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3 Comments

arena Over a year ago

but the collect is collecting to a list. My main point is to go through the list and get every elements as a new Person object. Or did I miss something? Thanks!

Ousmane D. Over a year ago

@arena Which is exactly what the code is doing. Going through all the elements and constructing new objects with the people names. If you don’t collect the new elements to a list then where will you store the new objects constructed ?

arena Over a year ago

Make sense! Thanks!

jkchu · Accepted Answer · 2018-06-27 23:25:41Z

-1

Just a simple forEach loop:

personList.forEach(p -> {
  T newObject = new T(p.getName());
  // Do what you need to do with each new object
});

If you are trying to do something more complicated, then Aonminè's answer is probably what you really need.

answered Jun 27, 2018 at 23:25

jkchu

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