A scalable concurrent
ConcurrentNavigableMap
implementation.
The map is sorted according to the
natural
ordering of its keys, or by a
Comparator
provided at map
creation time, depending on which constructor is used.
This class implements a concurrent variant of SkipLists providing
expected average log(n) time cost for the
containsKey, get, put and
remove operations and their variants. Insertion, removal,
update, and access operations safely execute concurrently by
multiple threads. Iterators are weakly consistent, returning
elements reflecting the state of the map at some point at or since
the creation of the iterator. They do not throw ConcurrentModificationException
, and may proceed concurrently with
other operations. Ascending key ordered views and their iterators
are faster than descending ones.
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, putIfAbsent, or
replace, depending on exactly which effect you need.)
Beware that, unlike in most collections, the size
method is not a constant-time operation. Because of the
asynchronous nature of these maps, determining the current number
of elements requires a traversal of the elements. Additionally,
the bulk operations putAll, equals, and
clear are not guaranteed to be performed
atomically. For example, an iterator operating concurrently with a
putAll operation might view only some of the added
elements.
This class and its views and iterators implement all of the
optional methods of the Map
and Iterator
interfaces. Like most other concurrent collections, this class does
not permit the use of null keys or values because some
null return values cannot be reliably distinguished from the absence of
elements.
This class is a member of the
Java Collections Framework.