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Mikki Halpin
Mikki Halpin

Total Post:23

Posted on    July-10-2015 1:00 AM

 Java Java  Collection  Array List 

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I read about sorting ArrayLists using a Comparator but in all of the examples people used compareTo which according to some research is a method for Strings.

I wanted to sort an ArrayList of custom objects by one of their properties: a Date object (getStartDay()). Normally I compare them by item1.getStartDate().before(item2.getStartDate()) so I was wondering whether I could write something like:
public class customComparator {
    public boolean compare(Object object1, Object object2) {
        return object1.getStartDate().before(object2.getStartDate());
public class randomName {
    Collections.sort(Database.arrayList, new customComparator);

Mayank Tripathi
Mayank Tripathi

Total Post:397

Posted on    July-10-2015 8:09 AM

With Java 8 you can use a method reference for your comparator:
import static java.util.Comparator.comparing;
Collections.sort(list, comparing(MyObject::getStartDate));\

JAVA 8 lambda expression
Collections.sort(studList, (Student s1, Student s2) ->{
        return s1.getFirstName().compareToIgnoreCase(s2.getFirstName());

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