java find duplicate element in list
public static Set<String> findDuplicates(List<String> listContainingDuplicates) {
final Set<String> setToReturn = new HashSet<String>();
final Set<String> set1 = new HashSet<String>();
for (String yourInt : listContainingDuplicates) {
if (!set1.add(yourInt)) {
setToReturn.add(yourInt);
}
}
return setToReturn;
}