Sort objects in ArrayList by date?

Question

Every example I find is about doing this alphabetically, while I need my elements sorted by date.

My ArrayList contains objects on which one of the datamembers is a

Answer 1

The Date class already implements Comparator interface. Assuming you have the class below:

public class A {

    private Date dateTime;

    public Date getDateTime() {
        return dateTime;
    }

    .... other variables

}

And let's say you have a list of A objects as List aList, you can easily sort it with Java 8's stream API (snippet below):

import java.util.Comparator;
import java.util.stream.Collectors;

...

aList = aList.stream()
        .sorted(Comparator.comparing(A::getDateTime))
        .collect(Collectors.toList())