Find specific object in a List by attribute

Question

I have a list:

List<UserItem> userList = new ArrayList<>();

Where I add the following:

User father = new User();
father.setName("Peter");

UserItem parent = new UserItem(father, null);
userList.add(parent);

I then create another user:

User daughter = new User();
daughter.setName("Emma");

UserItem child = new UserItem(daughter, <OBJECT IN LIST WHERE NAME IS "PETER">);
userList.add(child);

However, I need to change the text wrapped in <> above to the parent object I added before (the father), specified by the name ("Peter" in this case).

How can I find an object in a List by a specific attribute? In my case, how can I find the object in the List that has the name "Peter"?

Please note that I add hundreds, sometimes thousands, of different users like this to the list. Each "parent" has a unique name.

Answer 1

The obvious solution would be iterating on the list and when the condition is met, return the object:

for (User user : userList) {
    if ("peter".equals(user.getName()) {
        return user;
    }
}

And you can use filter (Java 8):

List<User> l = list.stream()
    .filter(s -> "peter".equals(s.getUser()))
    .collect(Collectors.toList());

to get a list with all "peter" users.

As suggested in comments, I think using Map is a better option here.