ArrayList sorting issue in Android

Question

I've an ArrayList of objects.

ArrayList<Item> blog_titles = new ArrayList<Item>();

I want to sort the ArrayList in the descending order of one of the datamembers which is a DateTime value stored as String (timestamp in the code below).

public class BlogItem implements Item, Comparable<BlogItem> {

    public final String id;
    public final String heading;
    public final String summary;
    public final String description;
    public final String thumbnail;
    public final String timestamp;  // format:- 2013-02-05T13:18:56-06:00
    public final String blog_link;

    public BlogItem(String id, String heading, String summary, String description, String thumbnail, String timestamp, String blog_link) {      
        this.id = id;
        this.heading = heading;
        this.summary = summary;
        this.description = description;
        this.thumbnail = thumbnail;
        this.timestamp = timestamp;   // format:- 2013-02-05T13:18:56-06:00
        this.blog_link = blog_link;
    }

    @Override
    public int compareTo(BlogItem o) {
        // TODO Auto-generated method stub
        return this.timestamp.compareTo(o.timestamp);
    }

}

Item is a generic interface:

public interface Item { 
   // TODO Auto-generated method stub
}

Now when i'm trying to sort the ArrayList like:

Collections.sort(blog_titles);

I get the following error message:

Bound mismatch: The generic method sort(List<T>) of type Collections is not applicable for the arguments (ArrayList<Item>). The inferred type Item is not a valid substitute for the bounded parameter <T extends Comparable<? super T>>

How do i fix the above error & is this the correct approach to sort the ArrayList in this case ?

Refer this link <a href="stackoverflow.com/questions/7514451/…> It will help you to sort out type data. — Sunil Kumar
– Sunil Kumar, Commented May 15, 2013 at 11:38
I've implemented the same concept which is mentioned in the solution...however i'm getting a different error msg here — Sourav
– Sourav, Commented May 15, 2013 at 12:10
Bound mismatch: The generic method sort(List<T>)... basically that's the issue here — Sourav
– Sourav, Commented May 15, 2013 at 12:30

njzk2 · Accepted Answer · 2013-05-15 11:32:25Z

3

Your blog_titles list is a list of Item.

Item itself is not Comparable, while BlogItem is.

Either declare blog_titles as a ArrayList<BlogItem>, or make Item extend Comparable

answered May 15, 2013 at 11:32

njzk2

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TheFlash · Accepted Answer · 2013-05-15 11:33:40Z

1

Try this..

Collections.sort(blog_titles, new Comparator<BlogItem>() {

        @Override
        public int compare(BlogItem lhs, BlogItem rhs) 
        {
            // TODO Auto-generated method stub
            return (int)(rhs.timestamp - lhs.timestamp);
        }
    });

answered May 15, 2013 at 11:33

TheFlash

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1 Comment

TheFlash Over a year ago

@Sourav here in my answer timestamp's datatype is long.

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