SplayTreeSet<E> class Null safety

A Set of objects that can be ordered relative to each other.

The set is based on a self-balancing binary tree. It allows most operations in amortized logarithmic time.

Elements of the set are compared using the compare function passed in the constructor, both for ordering and for equality. If the set contains only an object a, then set.contains(b) will return true if and only if compare(a, b) == 0, and the value of a == b is not even checked. If the compare function is omitted, the objects are assumed to be Comparable, and are compared using their Comparable.compareTo method. Non-comparable objects (including null) will not work as an element in that case.

Note: Do not modify a set (add or remove elements) while an operation is being performed on that set, for example in functions called during a forEach or containsAll call, or while iterating the set.

Do not modify elements in a way which changes their equality (and thus their hash code) while they are in the set. Some specialized kinds of sets may be more permissive with regards to equality, in which case they should document their different behavior and restrictions.

Example:

final planets = SplayTreeSet<String>((a, b) => a.compareTo(b));

To add data to a set, use add or addAll.

planets.add('Neptune');
planets.addAll({'Venus', 'Mars', 'Earth', 'Jupiter'});
print(planets); // {Earth, Jupiter, Mars, Neptune, Venus}

To check if the set is empty, use isEmpty or isNotEmpty. To find the number of elements in the set, use length.

final isEmpty = planets.isEmpty; // false
final length = planets.length; // 5

To check whether the set contains a specific element, use contains.

final marsExists = planets.contains('Mars'); // true

To get element value using index, use elementAt.

final elementAt = planets.elementAt(1);
print(elementAt); // Jupiter

To make a copy of set, use toSet.

final copySet = planets.toSet(); // a `SplayTreeSet` with the same ordering.
print(copySet); // {Earth, Jupiter, Mars, Neptune, Venus}

To remove an element, use remove.

final removedValue = planets.remove('Mars'); // true
print(planets); // {Earth, Jupiter, Neptune, Venus}

To remove multiple elements at the same time, use removeWhere.

planets.removeWhere((element) => element.startsWith('J'));
print(planets); // {Earth, Neptune, Venus}

To removes all elements in this set that do not meet a condition, use retainWhere.

planets.retainWhere((element) => element.contains('Earth'));
print(planets); // {Earth}

To remove all elements and empty the set, use clear.

planets.clear();
print(planets.isEmpty); // true
print(planets); // {}

See also:

• Set is a base-class for collection of objects.
• HashSet the order of the objects in the iterations is not guaranteed.
• LinkedHashSet objects stored based on insertion order.