Converting List of objects to an Array of Strings

Question

In my main class, I have: List<Person> allPeople = new ArrayList<>();

Then in the class I have a method which returns a String array of all the Id of people (Person has an accessor method getId() ).

What is the prettiest way to convert the list to an array with just the Ids as String?

This is my current solution:

public String[] getAllId() {

    Object[] allPeopleArray = allPeople.toArray();
    String allId[] = new String[allPeople.size()];              

    for(int i=0; i<=allPeople.size()-1; i++){
        allId[i] = ((Person)allPeopleArray [i]).getId();                    
    }

    return allId;
}

Above works, but is there a 'better' way to do this?

Do you need to return String[] or is List<String> acceptable? — user439793
– user439793, Commented Dec 29, 2014 at 16:10
possible duplicate of The easiest way to transform collection to array? — user289086
– user289086, Commented Dec 29, 2014 at 17:22
Not a duplicate, it's not just transforming to array, it's transforming to array of a specific property (in this case - id) — haimlit
– haimlit, Commented Dec 29, 2014 at 18:21

Marcelo Glasberg · Accepted Answer · 2014-12-29 23:19:40Z

6

public String[] getAllId() {
    return allPeople.stream().map(Person::getId).toArray(String[]::new);
}

edited Dec 29, 2014 at 23:19

answered Dec 28, 2014 at 17:47

Marcelo Glasberg

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1 Comment

user439793 Over a year ago

Please note that this answer requires new methods and syntax introduced in Java 8.

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