Java Utililty Methods List Merge

int total = 0;
for (int it : result) {
    total += it;
return total;

if (sourceList == null) {
    return filterSet;
for (Object ratinigAID : sourceList) {
    if (filterSet.contains(ratinigAID)) {
    } else {
        resultList.add(ratinigAID);
        filterSet.add(ratinigAID);
...

int size = list1.size() + list2.size();
for (List<? extends T> l : rest) {
    size += l.size();
List<T> result = new ArrayList<>(size);
result.addAll(list1);
result.addAll(list2);
for (List<? extends T> l : rest) {
...

list1.addAll(list2);
Collections.sort(list1);
return list1;

List<String> list = new ArrayList<String>(Arrays.asList(new String[list1.size()]));
Collections.copy(list, list1);
list.addAll(list2);
return list;

List<T> result = list == null ? new ArrayList<>() : new ArrayList<>(list);
for (List<T> other : others)
    result.addAll(other);
return result;

if (isAllNull(one, two))
    return null;
List<T> result = new ArrayList<>();
if (isAllNotNull(one, two)) {
    result.addAll(one);
    for (T t : two) {
        if (one.indexOf(t) == -1) {
            result.add(t);
...

final ArrayList<T> retValue = new ArrayList<T>();
Collections.addAll(retValue, array);
return retValue;