Re: Comparing Collections

[James Perkins <jrperkinsjr@xxxxxxxxx>]

Good catch! I actually had that in my original code, but when I "cleaned" it
up I removed it for what ever reason.

Updated version:

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

/**
 * @author James R Perkins (JRP)
 * @version 1.0.0
 */
public class CollectionsUtil {
    private CollectionsUtil() {

    }

    /**
     * Compares the first collection against the second collection. Returns
a
     * negative integer, zero or positive integer.
     * <p>
     * If the size of the first collection is greater than the size of the
     * second collection, a positive integer is return. If the size of the
first
     * collection is less than the size of the second collection a negative
     * number is returned.
     * </p>
     *
     * <p>
     * If the size of the two collections is equal, then each element from
     * collection 1 is compared to the element in the same position from
     * collection 2.
     * </p>
     *
     * @param <T>
     *            the type of the collection. Both collections must be the
same
     *            type and implement {@code java.lang.Comparable}.
     * @param c1
     *            the first collection to be compared
     * @param c2
     *            the second collection to be compared
     * @return a negative integer, zero, or a positive integer as the first
     *         argument is less than, equal to, or greater than the second.
     */
    public static <T extends Comparable<? super T>> int compare(
            Collection<T> c1, Collection<T> c2) {
        int c = c1.size() - c2.size();
        if (c != 0)
            return c;
        List<T> l1 = new ArrayList<T>(c1);
        List<T> l2 = new ArrayList<T>(c2);
        for (int i = 0; i < l1.size(); i++) {
            c = l1.get(i).compareTo(l2.get(i));
            if (c != 0) {
                break;
            }
        }
        return c;
    }
}

--
James R. Perkins
http://twitter.com/the_jamezp


On Wed, Sep 2, 2009 at 16:13, M. Lazarus <mlazarus@xxxxxxxx> wrote:

> James,
>
>  Why not do the test for an unequal number of elements, and execute
> a return, before entering the loop?
>
>  -mark