Java 8 How to manipulate objects in one list and collect them in another list? [duplicate]

Question

I'm fairly new to Java8. I have a requirement to convert List of POJOs to group by a certain criteria and show it on UI.

Convert list of objects that belong to Children category to Person category.

Return the List.

Children.java
private String firstName;
private String lastName;
private String school;
private String personId;
// Setters and getters.

Person.java
private String fullName;
private String address;
// Setters and Getters.

private Person convertChildToPerson(Children child) {
         Person person = new Person();
         person.setFullName(child.getLastName() + ", " + child.getFirstName());
          ..
          return person;
 }

.. MAIN CODE.. ..

List<Person> personList;  // Is populated by other functions.

// Connect to DB and gets the output
List<Children> childrenList = (Children) criteria.list();  

for(Children children: childrenList) {
     personList.add(convertChildToPerson(children));
}
return personList;

Can't the FOR-LOOP present above be replaced by Java 8 Streams?

See the answer from Robert Bräutigam

Adesh Kumar
– Adesh Kumar

2018-02-27 19:14:48 +00:00
Commented Feb 27, 2018 at 19:14 — Adesh Kumar
– Adesh Kumar, Commented Feb 27, 2018 at 19:14

Eugene · Accepted Answer · 2018-02-28 08:55:49Z

4

 List<Person> newList = childrenList.stream()
             .map(this::convertChildToPerson)
             .collect(Collectors.toList());

 personList.addAll(newList);

Even shorter (and nicer), as suggested by Holger:

childrenList.stream()
            .map(this::convertChildToPerson)
            .forEachOrdered(personList::add);

edited Feb 28, 2018 at 8:55

answered Feb 27, 2018 at 19:01

Eugene

122k17 gold badges219 silver badges335 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Srinivas Lakshman Over a year ago

Thanks for the reply Eugene. But I already have personList which has been populated by other methods. I can't override that... So, should I have to do personList1 = ..... and then personList.addAll(personList1) ?

Eugene Over a year ago

@SrinivasLakshman right, see edit

Holger Over a year ago

forEachOrdered(personList::add) would work too. Collecting into a new list before adding them at once may look cleaner, but implies needing temporary storage.

Eugene Over a year ago

@Holger good suggestion, thx

Collectives™ on Stack Overflow

Java 8 How to manipulate objects in one list and collect them in another list? [duplicate]

1 Answer 1

4 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Linked

Related