Which gives better performance

Question

I have to two arraylists. I have to sort one based on the other. The way i did was to iterate one over the other. Or may be I have to load one arrylist into a hashmap and then do hashmap.get to get to the individual items?
MR

Answer 1

I find this an interesting problem so I had a go at it just to understand what one has to do -
import java.util.*;
public class Fred
    public static void main(String[] args)
        // Create the reference
        final ArrayList<Integer> reference = new ArrayList<Integer>();
        for (int index = 0; index < 100; index++)
            reference.add(index);
        Collections.shuffle(reference);
        // Now some data to work with
        final Random random = new Random();
        final ArrayList<Integer> data = new ArrayList<Integer>();
        for (int index = 0; index < 1000; index++)
            data.add(random.nextInt(100));
        // Build the map needed in the sort comparator
        final HashMap<Integer,Integer> sortHelper = new HashMap<Integer,Integer>();
        for (int index = 0; index < reference.size(); index++)
            sortHelper.put(reference.get(index), index);
        // The 'indirect' comparator
        final Comparator<Integer> comparator = new Comparator<Integer>()
            public int compare(Integer left, Integer right)
                Integer leftIndex = sortHelper.get(left);
                Integer rightIndex = sortHelper.get(right);
                if (leftIndex == null)
                    return 1;
                else
                    return leftIndex.compareTo(rightIndex);
        // Now sort
        Collections.sort(data, comparator);
        // Test the result - how?
}So how does one test the result?