How to sort an ArrayList of custom object by property in Java

Question

I want to sort an ArrayList of custom object by Date object property. How can I do it?

Answer 1

As we are using Date property of ArrayList, we can use compareTo() method, because Date implements comparable.

public class CustomComparator implements Comparator<MyObject> {
    @Override
    public int compare(MyObject o1, MyObject o2) {
        return o1.getStartDate().compareTo(o2.getStartDate());
    }
}

comapreTo() returns int value.

Collections.sort(Database.arrayList, new CustomComparator());

Answer 2

You can Sort using java 8

yourList.sort(Comparator.comparing(Classname::getName));

or 

yourList.stream().forEach(a -> a.getBObjects().sort(Comparator.comparing(Classname::getValue)));