Java Utililty Methods Collection Union

List of utility methods to do Collection Union

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Description

The list of methods to do Collection Union are organized into topic(s).

Method

Listunion(Collection c1, Collection c2)
union 
List collection = new ArrayList();
collection.addAll(c1);
collection.addAll(c2);
return collection;
Setunion(Collection coll)
Returns the union of all the sets given in a collection. 
Set set = new HashSet();
for (Iterator i = coll.iterator(); i.hasNext();) {
    set.addAll((Collection) i.next());
return set;
Collectionunion(Collection collection1, Collection collection2)
Given two collections of elements of type , return a collection containing the items from both lists 
if (isEmpty(collection1)) {
    if (isEmpty(collection2)) {
        return Collections.emptyList();
    return new ArrayList<T>(collection2);
if (isEmpty(collection2)) {
    return new ArrayList<T>(collection1);
...
Listunion(Collection c1, Collection c2)
Adds all elements of two collections to a new LinkedList. 
List<E> result = new LinkedList<E>();
result.addAll(c1);
result.addAll(c2);
return result;
Setunion(Collection> sets)
Determines the union of a collection of sets. 
Set<T> result = new HashSet<>();
if (sets.isEmpty()) {
    return result;
Iterator<Set<T>> iter = sets.iterator();
result.addAll(iter.next());
if (sets.size() == 1) {
    return result;
...
Collectionunion(Collection a, Collection b)
Union of two collections with duplicates 
return null;
Listunion(Collection c1, Collection c2)
intersection of c1 and c2, does not change input collections, returns new collection (list) 
if (c1 == null && c2 == null) {
    return Collections.emptyList();
if (c1 == null) {
    return new ArrayList<>(c2);
if (c2 == null) {
    return new ArrayList<>(c1);
...
Listunion(Collection initial, Collection other)
returns a List of union objects, i.e. 
ArrayList<T> union = new ArrayList<T>();
for (T obj : initial) {
    if (other.contains(obj))
        union.add(obj);
return union;
Setunion(Collection lhs, Collection rhs)
union 
HashSet<T> results = new HashSet<>(lhs.size() + rhs.size());
results.addAll(lhs);
results.addAll(rhs);
return results;
Collectionunion(Collection set1, Collection set2)
union 
Collection<T> union = new ArrayList<>();
for (T t : set1) {
    union.add(t);
for (T t : set2) {
    union.add(t);
return union;
...