How can we compare objects by multiple fields in Java

Question

We have some objects which have several fields they can be compared by:

public class Person {

    private String firstName;
    private String lastName;
    private String age;

    /* Constructors */

    /* Methods */

}

So in this example, when you ask if:

a.compareTo(b) > 0

you might be asking if a's last name comes before b's, or if a is older than b, etc...

What is the cleanest way to enable multiple comparison between these kinds of objects without adding unnecessary clutter or overhead?

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Answer 1

You can implement a Comparator which compares two Person objects, and you can examine as many of the fields as you like. You can put in a variable in your comparator that tells it which field to compare to, although it would probably be simpler to just write multiple comparators.