Find specific object in a List by attribute

Question

I have a list:

List userList = new ArrayList<>();

Where I add the following:

User father = new User()         


        

Answer 1

Answer to your question is here: https://stackoverflow.com/a/1385698/2068880

Stream peters = userList.stream().filter(p -> p.user.name.equals("Peter"))

However, as ruakh suggested, it's more reasonable to use Map<String, UserItem> to make it faster. Otherwise, it will iterate all the objects in the list to find users with name "Peter".

Answer 2

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.

Answer 3

Other way with parallelStream with findAny

Optional<UserItem> optional = userList.parallelStream().findAny(p -> p.user.getName().equalsIgnoreCase("Peter"));
UserItem user = optional.isPresent() ? optional.get() : null;