Set.addAll()
Merges a set with another collection (union).
Available since: Java 1.2
Syntax
boolean addAll(Collection<? extends E> c)Parameters
| Parameter | Type | Description |
|---|---|---|
| c | Collection<? extends E> | The collection of elements to add. |
Return value
boolean`true` if the set changed.
Examples
The union of two sets:
void main() {
Set<String> union = new TreeSet<>(Set.of("java", "sql"));
union.addAll(Set.of("sql", "git"));
IO.println(union);
}Output:
[git, java, sql]Notes
The method changes the set it is called on. To keep the source data intact, copy it first: new HashSet<>(a), then addAll(b). retainAll() gives the intersection and removeAll() the difference.
See also
- Set.retainAll() — Keeps only the elements that are also in another collection (intersection).
- Set.removeAll() — Removes all elements of another collection from a set (difference).
- List.addAll() — Adds all elements of another collection to a list.
In the tutorial
- Sets: Set — Sets in Java: HashSet without duplicates, LinkedHashSet and TreeSet with ordering, union and intersection of sets.