import java.util.ArrayList;
import java.util.Collection;
public class Utils {
public static Collection diff(Collection c1, Collection c2) {
if (c1 == null || c1.size() == 0 || c2 == null || c2.size() == 0) {
return c1;
}
Collection difference = new ArrayList();
for (T item : c1) {
if (!c2.contains(item)) {
difference.add(item);
}
}
return difference;
}
}