1 
 2 public class CollectionModificationHelper {
 3 
 4 public static List getCommonElements(List oldCollection, List newCollection) {
 5 //iterate on oldCollection and find the common elements
 6 }
 7 
 8 public static List getNewElements(List oldCollection, List newCollection) {
 9 //iterate on newCollection and find the new elements
10 }
11 
12 public static List getRemovedElements(List oldCollection, List newCollection) {
13 //iterate on oldCollection and find the deleted elements
14 }
15 }