A TreeSet is implemented as a Red-Black Tree, a self-balancing binary search tree, so most of its operations have logarithmic complexity O(log n).
Constructor Summary
| Constructor | Description |
| TreeSet() | Constructs a new, empty tree set, sorted according to the natural ordering of its elements. |
| TreeSet(Collection<? extends E> c) | Constructs a new tree set containing the elements in the specified collection, sorted according to the natural ordering of its elements. |
| TreeSet(Comparator<? super E> comparator) | Constructs a new, empty tree set, sorted according to the specified comparator. |
| TreeSet(SortedSet<E> s) | Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set. |
Method Summary:
| Method | Complexity |
| add(E e) | O(logn) |
| addAll(Collection<? extends E> c) | O(m⋅log(n+m)) |
| remove(Object o) | O(logn) |
| pollFirst() | O(logn) |
| pollLast() | O(logn) |
| contains(Object o) | O(logn) |
| first() | O(1) |
| last() | O(1) |
| higher(E e) | O(logn) ; Returns the least element in this set strictly greater than the given element, or null if there is no such element. |
| lower(E e) | O(logn) ; Returns the greatest element in this set strictly less than the given element, or null if there is no such element. |
| size() | O(1) |
Iterating over TreeSet:
TreeSet<String> treeSet = new TreeSet<>();
treeSet.add("Apple");
treeSet.add("Banana");
treeSet.add("Cherry");
// Enhanced for loop
for (String element : treeSet) {
System.out.println(element);
}
// Using Iterator
Iterator<String> iterator = treeSet.iterator();
while (iterator.hasNext()) {
String element = iterator.next();
System.out.println(element);
}
// Using Lambda expression
treeSet.forEach(element -> System.out.println(element));
// Using stream
treeSet.stream().forEach(System.out::println);