How to find Max Date in List<Object>?

Question

Consider a class User

public class User{
  int userId;
  String name;
  Date date;
}

Now I have a List

Answer 1

You should not call .get() directly. Optional<>, that Stream::max returns, was designed to benefit from .orElse... inline handling.

If you are sure your arguments have their size of 20:

list.stream()
    .map(u -> u.date)
    .max(Date::compareTo)
    .orElseThrow(() -> new IllegalArgumentException("Expected a list of size: 20. Was: 0"));

If you support empty lists, then return some default value, for example:

list.stream()
    .map(u -> u.date)
    .max(Date::compareTo)
    .orElse(new Date(Long.MIN_VALUE));

CREDITS to: @JimmyGeers, @assylias from the accepted answer.