Question

This is what I have:

class Person {
  Integer id;
  String name;
}

// A list of persons:
List<Person> persons

// Now I have something like this:
List<Integer> ids  // where the ids are stored in an specific order

Basically I wanna sort the persons list in the same order like the ids.

Is there a better way then use like two loops and create a new Person-List?

regards && tia

noircc

Answer 1

Use Collections.sort using a custom Comparator as shown below. The comparator gets the ids of the persons being compared and works out in which order they appear in the ids list:

List<Person> persons = ...;
final List<Integer> ids = ...;

Collections.sort(persons, new Comparator<Person>() {
    @Override
    public int compare(Person p1, Person p2) {
        int index1 = ids.indexOf(p1.getId());
        int index2 = ids.indexOf(p2.getId());
        return index1 < index2 ? -1 : (index1 == index2 ? 0 : 1);
    }
});

Note: this code assumes that the ids of all persons in the list will appear in the ids list.