Android sort arraylist by properties

Question

I want to sort an ArrayList by a property. This is my code...

public class FishDB{

    public static Object Fish;
    public ArrayList<Fish> list = new ArrayList<Fish>();

    public class Fish{
        String name;
        int length;
        String LatinName;
        //etc. 

        public Vis (String name) {
            this.name = name;
        }
    }

    public FishDB() {
        Fish fish;

        fish = new Fish("Shark");
        fish.length = 200;
        fish.LatinName = "Carcharodon Carcharias";

        fish = new Fish("Rainbow Trout");
        fish.length = 80;
        fish.LatinName = "Oncorhynchus Mykiss";

        //etc.
        }
    }
}

Now I want in want to sort this ArrayList by a property e.g the latinname in another activity. But I don't know how to do that. Does anybody know how?

Solution 1

You need to implement a Comparator, for instance:

public class FishNameComparator implements Comparator<Fish>
{
    public int compare(Fish left, Fish right) {
        return left.name.compareTo(right.name);
    }
}

and then sort it like this:

Collections.sort(fishes, new FishNameComparator());

Solution 2

You can simply do it by this code:

Collections.sort(list, new Comparator<Fish>() {
    public int compare(Fish o1, Fish o2) {
        return o1.name.compareTo(o2.name);
    }
});

Solution 3

Kotlin code

list.sortWith(Comparator { o1, o2 -> o1.name!!.compareTo(o2.name!!) })

Comments

[Simon]

Thanks, but i still have one problem. I want to sort the arraylist in an activity. At the beginning stands: public class fishList extends ListActivity{ And when I write public class FishNameComparator implements Comparator<String>{ It gives two errors saying: illegal modifier for the local class FishNameComparator; only abstract or final is permitted. And: The type FishNameComparator must implement the inherited abstract method Comparator<String>.compare(String, String). I just did what stands in your answer.

[K-ballo]

@user1380611: If you are implementing this as a nested class, then it has to be a static class. And I messed up my example, it should be implements Comparator<Fish>.

[IgorGanapolsky]

Works perfectly for me. Sorts in ascending order here.

[imike]

This one much better!