Getting object with max date property from list of objects Java 8

Question

I have a class called Contact that has a Date lastUpdated; variable.

I would like to pull the Contact out of a List

Answer 1

and the Contact class should not always use the lastUpdated variable for comparing instances

So you will have to provide a custom comparator whenever you want to compare multiple instances by their lastUpdated property, as it implies that this class is not comparable by default with this field.

Comparator<Contact> cmp = Comparator.comparing(Contact::getLastUpdated);

As you know you can either use Collections.max or the Stream API to get the max instance according to this field, but you can't avoid writing a custom comparator.

Answer 2

Writing custom comparator in Java-8 is very simple. Use:

Comparator.comparing(c -> c.lastUpdated);

So if you have a List<Contact> contacts, you can use

Contact lastContact = Collections.max(contacts, Comparator.comparing(c -> c.lastUpdated));

Or, using method references:

Contact lastContact = Collections.max(contacts, Comparator.comparing(Contact::getLastUpdated));

Answer 3

Use List<T>.stream().max(Comparator<T>).get() after you defined a suitable Comparator.

Answer 4

Try the following (untested):

contacts.stream().max(Comparator.comparing(Contact::getLastUpdated)).get()