Question

I have some lists that contain elements of type DataTime( Joda-time ). How can I sort them by date?
It will be great if somebody gave link to the example…

Answer 1

Because the objects of your list implement the Comparable interface, you can use

Collections.sort(list);

where list is your ArrayList.

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Relevant Javadocs:

• Collections
• DateTime
• Comparable

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Edit: If you want to sort a list of a custom class that contains a DateTime field in a similar way, you would have to implement the Comparable interface yourself. For example,

public class Profile implements Comparable<Profile> { 
    DateTime date;
    double age; 
    int id; 

    ...

    @Override
    public int compareTo(Profile other) {
        return date.compareTo(other.getDate());  // compare by date
    }
}

Now, if you had a List of Profile instances, you could employ the same method as above, namely Collections.sort(list) where list is the list of Profiles.