How to find the index of an arraylist item, using a property in a list item?

Question

//what is the best way to find out the index of a particular event using the Offer Id?
using core java or using a third-party library like (Guava/Commons Collection)?

  public class Event{
        private String title;
        //other attributes
        private ArrayList<Offers> lOffers;
    }

    public class Offers{
        private Sring Id;
        private String offerName;
    }


    //Code
    List<PayPerViewTitles>  PayPerViewTitleList = someMethod();

/*

offerId -> Offers Object id property
**/
    private int findEventPositionByOfferId(List<Event> eventList, String offerId){
       // how to implement this method to find the Main Event using the 
       offer->id
    }

This Object is used to Map the server JSON Response,

Answer 1

you can use a map to save id as key,object as value,then use list,like this:

List<Student> students = new ArrayList<>();
    Student student0 = Student.builder().id(1).name("wentjiang").age(23).build();
    Student student1 = Student.builder().id(2).name("wentjiang2").age(232).build();

    Map<Integer,Student> map = new HashMap<>();
    map.put(student0.getId(),student0);
    map.put(student1.getId(),student1);
    students.add(student0);
    students.add(student1);
    Integer findId = 2;
    Student student = map.get(findId);
    int index = students.indexOf(student);
    System.out.println(index);