java.util.AbstractMap<K,V>
org.apache.commons.collections4.trie.AbstractBitwiseTrie<K,V>
org.apache.commons.collections4.trie.PatriciaTrie<E>
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java.lang.Object
public class PatriciaTrie<E>
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 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 prefixMap(Object) are suited only
to variable length keys.
| Nested Class Summary | |
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protected static class |
AbstractPatriciaTrie.TrieEntry<K,V>
A Trie is a set of AbstractPatriciaTrie.TrieEntry nodes. |
| Field Summary | |
|---|---|
protected int |
modCount
The number of times this Trie has been modified. |
| Constructor Summary | |
|---|---|
PatriciaTrie()
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PatriciaTrie(Map<? extends String,? extends E> m)
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| Method Summary | |
|---|---|
void |
clear()
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Comparator<? super K> |
comparator()
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boolean |
containsKey(Object k)
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Set<Map.Entry<K,V>> |
entrySet()
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K |
firstKey()
Gets the first key currently in this map. |
V |
get(Object k)
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int |
hashCode()
Gets the standard Map hashCode. |
SortedMap<K,V> |
headMap(K toKey)
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Set<K> |
keySet()
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K |
lastKey()
Gets the last key currently in this map. |
OrderedMapIterator<K,V> |
mapIterator()
Obtains a MapIterator over the map. |
K |
nextKey(K key)
Gets the next key after the one specified. |
SortedMap<K,V> |
prefixMap(K key)
Returns a view of this Trie of all elements that are prefixed
by the given key. |
K |
previousKey(K key)
Gets the previous key before the one specified. |
V |
put(K key,
V value)
Note that the return type is Object, rather than V as in the Map interface. |
V |
remove(Object k)
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Map.Entry<K,V> |
select(K key)
Returns the AbstractPatriciaTrie.TrieEntry whose key is closest in a bitwise XOR
metric to the given key. |
K |
selectKey(K key)
Returns the key that is closest in a bitwise XOR metric to the provided key. |
V |
selectValue(K key)
Returns the value whose key is closest in a bitwise XOR metric to the provided key. |
int |
size()
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SortedMap<K,V> |
subMap(K fromKey,
K toKey)
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SortedMap<K,V> |
tailMap(K fromKey)
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Collection<V> |
values()
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| Methods inherited from class org.apache.commons.collections4.trie.AbstractBitwiseTrie |
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getKeyAnalyzer, toString |
| Methods inherited from class java.util.AbstractMap |
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clone, containsValue, equals, isEmpty, putAll |
| Methods inherited from class java.lang.Object |
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finalize, getClass, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface org.apache.commons.collections4.Trie |
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prefixMap |
| Methods inherited from interface java.util.SortedMap |
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comparator, firstKey, headMap, lastKey, subMap, tailMap |
| Methods inherited from interface org.apache.commons.collections4.OrderedMap |
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firstKey, lastKey, mapIterator, nextKey, previousKey |
| Methods inherited from interface org.apache.commons.collections4.Put |
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clear, put, putAll |
| Methods inherited from interface org.apache.commons.collections4.Get |
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containsKey, containsValue, entrySet, get, isEmpty, keySet, remove, size, values |
| Field Detail |
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protected transient int modCount
Trie has been modified.
It's used to detect concurrent modifications and fail-fast the Iterators.
| Constructor Detail |
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public PatriciaTrie()
public PatriciaTrie(Map<? extends String,? extends E> m)
| Method Detail |
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public void clear()
clear in interface Map<K,V>clear in interface Put<K,V>clear in class AbstractMap<K,V>Map.clear()public int size()
size in interface Map<K,V>size in interface Get<K,V>size in class AbstractMap<K,V>Map.size()
public V put(K key,
V value)
Put
put in interface Map<K,V>put in interface Put<K,V>put in class AbstractMap<K,V>Map.put(Object, Object)public V get(Object k)
get in interface Map<K,V>get in interface Get<K,V>get in class AbstractMap<K,V>Map.get(Object)public Map.Entry<K,V> select(K key)
AbstractPatriciaTrie.TrieEntry whose key is closest in a bitwise XOR
metric to the given key. This is NOT lexicographic closeness.
For example, given the keys:
Trie contained 'H' and 'L', a lookup of 'D' would
return 'L', because the XOR distance between D & L is smaller
than the XOR distance between D & H.
key - the key to use in the search
AbstractPatriciaTrie.TrieEntry whose key is closest in a bitwise XOR metric
to the provided keypublic K selectKey(K key)
Trie contained 'H' and 'L', a lookup of 'D' would
return 'L', because the XOR distance between D & L is smaller
than the XOR distance between D & H.
key - the key to use in the search
public V selectValue(K key)
Trie contained 'H' and 'L', a lookup of 'D' would
return 'L', because the XOR distance between D & L is smaller
than the XOR distance between D & H.
key - the key to use in the search
public boolean containsKey(Object k)
containsKey in interface Map<K,V>containsKey in interface Get<K,V>containsKey in class AbstractMap<K,V>Map.containsKey(Object)public Set<Map.Entry<K,V>> entrySet()
entrySet in interface Map<K,V>entrySet in interface Get<K,V>entrySet in class AbstractMap<K,V>Map.entrySet()public Set<K> keySet()
keySet in interface Map<K,V>keySet in interface Get<K,V>keySet in class AbstractMap<K,V>Map.keySet()public Collection<V> values()
values in interface Map<K,V>values in interface Get<K,V>values in class AbstractMap<K,V>Map.values()public V remove(Object k)
remove in interface Map<K,V>remove in interface Get<K,V>remove in class AbstractMap<K,V>ClassCastException - if provided key is of an incompatible typeMap.remove(Object)public int hashCode()
hashCode in interface Map<K,V>hashCode in class AbstractMap<K,V>public Comparator<? super K> comparator()
comparator in interface SortedMap<K,V>public K firstKey()
OrderedMap
firstKey in interface SortedMap<K,V>firstKey in interface OrderedMap<K,V>public K lastKey()
OrderedMap
lastKey in interface SortedMap<K,V>lastKey in interface OrderedMap<K,V>public K nextKey(K key)
OrderedMap
nextKey in interface OrderedMap<K,V>key - the key to search for next from
public K previousKey(K key)
OrderedMap
previousKey in interface OrderedMap<K,V>key - the key to search for previous from
public OrderedMapIterator<K,V> mapIterator()
IterableGetMapIterator over the map.
A map iterator is an efficient way of iterating over maps. There is no need to access the entry set or use Map Entry objects.