A Red-Black tree based NavigableMap implementation.
The map is sorted according to the natural of its keys, or by a Comparator provided at map
creation time, depending on which constructor is used.
This implementation provides guaranteed log(n) time cost for the
containsKey, get, put and remove
operations. Algorithms are adaptations of those in Cormen, Leiserson, and
Rivest's Introduction to Algorithms.
Note that the ordering maintained by a tree map, like any sorted map, and
whether or not an explicit comparator is provided, must be consistent
with equals if this sorted map is to correctly implement the
Map interface. (See Comparable or Comparator for a
precise definition of consistent with equals.) This is so because
the Map interface is defined in terms of the equals
operation, but a sorted map performs all key comparisons using its
compareTo (or compare) method, so two keys that are deemed equal by
this method are, from the standpoint of the sorted map, equal. The behavior
of a sorted map is well-defined even if its ordering is
inconsistent with equals; it just fails to obey the general contract
of the Map interface.
Note that this implementation is not synchronized.
If multiple threads access a map concurrently, and at least one of the
threads modifies the map structurally, it must be synchronized
externally. (A structural modification is any operation that adds or
deletes one or more mappings; merely changing the value associated
with an existing key is not a structural modification.) This is
typically accomplished by synchronizing on some object that naturally
encapsulates the map.
If no such object exists, the map should be "wrapped" using the
Collections.synchronizedSortedMap
method. This is best done at creation time, to prevent accidental
unsynchronized access to the map:
SortedMap m = Collections.synchronizedSortedMap(new TreeMap(...));
The iterators returned by the iterator method of the collections
returned by all of this class's "collection view methods" are
fail-fast: if the map is structurally modified at any time after
the iterator is created, in any way except through the iterator's own
remove method, the iterator will throw a 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 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.
All Map.Entry pairs returned by methods in this class
and its views represent snapshots of mappings at the time they were
produced. They do not support the Entry.setValue
method. (Note however that it is possible to change mappings in the
associated map using put.)
This class is a member of the Java Collections Framework.
extends
<K> | the type of keys maintained by this map | |
<V> | the type of mapped values |
Map, HashMap, Hashtable, Comparable, Comparator, Collection