A {@link NavigableSet} implementation based on a {@link TreeMap}. The elements are ordered using their {@linkplain Comparable naturalordering}, or by a {@link Comparator} provided at set creationtime, depending on which constructor is used.
This implementation provides guaranteed log(n) time cost for the basic operations ( {@code add}, {@code remove} and {@code contains}).
Note that the ordering maintained by a set (whether or not an explicit comparator is provided) must be consistent with equals if it is to correctly implement the {@code Set} interface. (See {@code Comparable}or {@code Comparator} for a precise definition of consistent withequals.) This is so because the {@code Set} interface is defined interms of the {@code equals} operation, but a {@code TreeSet} instanceperforms all element comparisons using its {@code compareTo} (or{@code compare}) method, so two elements that are deemed equal by this method are, from the standpoint of the set, equal. The behavior of a set is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the {@code Set} interface.
Note that this implementation is not synchronized. If multiple threads access a tree set concurrently, and at least one of the threads modifies the set, it must be synchronized externally. This is typically accomplished by synchronizing on some object that naturally encapsulates the set. If no such object exists, the set should be "wrapped" using the {@link Collections#synchronizedSortedSet Collections.synchronizedSortedSet}method. This is best done at creation time, to prevent accidental unsynchronized access to the set:
SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));
The iterators returned by this class's {@code iterator} method arefail-fast: if the set is modified at any time after the iterator is created, in any way except through the iterator's own {@code remove}method, the iterator will throw a {@link ConcurrentModificationException}. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.
Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw {@code ConcurrentModificationException} on a best-effort basis.Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.
This class is a member of the Java Collections Framework.
@param < E> the type of elements maintained by this set
@author Josh Bloch
@version 1.37, 05/10/06
@see Collection
@see Set
@see HashSet
@see Comparable
@see Comparator
@see TreeMap
@since 1.2