Package org.apache.commons.collections4.trie

Class PatriciaTrie<V>

java.lang.Object
java.util.AbstractMap<K,V>
org.apache.commons.collections4.trie.AbstractBitwiseTrie<K,V>
org.apache.commons.collections4.trie.AbstractPatriciaTrie<String,V>
org.apache.commons.collections4.trie.PatriciaTrie<V>
Type Parameters:
V - the type of the values in this map
All Implemented Interfaces:
Serializable, Map<String,V>, SortedMap<String,V>, Get<String,V>, IterableGet<String,V>, IterableMap<String,V>, IterableSortedMap<String,V>, OrderedMap<String,V>, Put<String,V>, Trie<String,V>
public class PatriciaTrie<V> extends AbstractPatriciaTrie<String,V>
Implementation of a PATRICIA Trie (Practical Algorithm to Retrieve Information Coded in Alphanumeric).

A PATRICIA Trie is a compressed Trie. Instead of storing all data at the edges of the Trie (and having empty internal nodes), PATRICIA stores data in every node. This allows for very efficient traversal, insert, delete, predecessor, successor, prefix, range, and AbstractPatriciaTrie.select(Object) operations. All operations are performed at worst in O(K) time, where K is the number of bits in the largest item in the tree. In practice, operations actually take O(A(K)) time, where A(K) is the average number of bits of all items in the tree.

Most importantly, PATRICIA requires very few comparisons to keys while doing any operation. While performing a lookup, each comparison (at most K of them, described above) will perform a single bit comparison against the given key, instead of comparing the entire key to another key.

The Trie can return operations in lexicographical order using the 'prefixMap', 'submap', or 'iterator' methods. The Trie can also scan for items that are 'bitwise' (using an XOR metric) by the 'select' method. Bitwise closeness is determined by the KeyAnalyzer returning true or false for a bit being set or not in a given key.

This PATRICIA Trie supports both variable length & fixed length keys. Some methods, such as Trie.prefixMap(Object) are suited only to variable length keys.

Since:
4.0
See Also: