org.apache.mahout.cf.taste.impl.common
Class FastMap<K,V>

java.lang.Object
  extended by org.apache.mahout.cf.taste.impl.common.FastMap<K,V>
All Implemented Interfaces:
Serializable, Cloneable, Map<K,V>

public final class FastMap<K,V>
extends Object
implements Map<K,V>, Serializable, Cloneable

This is an optimized Map implementation, based on algorithms described in Knuth's "Art of Computer Programming", Vol. 3, p. 529.

It should be faster than HashMap in some cases, but not all. Its main feature is a "max size" and the ability to transparently, efficiently and semi-intelligently evict old entries when max size is exceeded.

This class is not a bit thread-safe.

This implementation does not allow null as a key or value.

See Also:
Serialized Form

Nested Class Summary
 
Nested classes/interfaces inherited from interface java.util.Map
Map.Entry<K,V>
 
Field Summary
static int NO_MAX_SIZE
           
 
Constructor Summary
FastMap()
          Creates a new FastMap with default capacity.
FastMap(int size)
           
FastMap(int size, float loadFactor)
           
FastMap(int size, int maxSize)
           
FastMap(int size, int maxSize, float loadFactor)
          Creates a new whose capacity can accommodate the given number of entries without rehash.
FastMap(Map<K,V> other)
           
 
Method Summary
 void clear()
           
 FastMap<K,V> clone()
           
 boolean containsKey(Object key)
           
 boolean containsValue(Object value)
           
 Set<Map.Entry<K,V>> entrySet()
           
 boolean equals(Object other)
           
 V get(Object key)
           
 int hashCode()
           
 boolean isEmpty()
           
 Set<K> keySet()
           
 V put(K key, V value)
           
 void putAll(Map<? extends K,? extends V> map)
           
 void rehash()
           
 V remove(Object key)
           
 int size()
           
 String toString()
           
 Collection<V> values()
           
 
Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

NO_MAX_SIZE

public static final int NO_MAX_SIZE
See Also:
Constant Field Values
Constructor Detail

FastMap

public FastMap()
Creates a new FastMap with default capacity.


FastMap

public FastMap(int size)

FastMap

public FastMap(Map<K,V> other)

FastMap

public FastMap(int size,
               float loadFactor)

FastMap

public FastMap(int size,
               int maxSize)

FastMap

public FastMap(int size,
               int maxSize,
               float loadFactor)
Creates a new whose capacity can accommodate the given number of entries without rehash.

Parameters:
size - desired capacity
maxSize - max capacity
Throws:
IllegalArgumentException - if size is less than 0, maxSize is less than 1 or at least half of RandomUtils.MAX_INT_SMALLER_TWIN_PRIME, or loadFactor is less than 1
Method Detail

get

public V get(Object key)
Specified by:
get in interface Map<K,V>

size

public int size()
Specified by:
size in interface Map<K,V>

isEmpty

public boolean isEmpty()
Specified by:
isEmpty in interface Map<K,V>

containsKey

public boolean containsKey(Object key)
Specified by:
containsKey in interface Map<K,V>

containsValue

public boolean containsValue(Object value)
Specified by:
containsValue in interface Map<K,V>

put

public V put(K key,
             V value)
Specified by:
put in interface Map<K,V>
Throws:
NullPointerException - if key or value is null

putAll

public void putAll(Map<? extends K,? extends V> map)
Specified by:
putAll in interface Map<K,V>

remove

public V remove(Object key)
Specified by:
remove in interface Map<K,V>

clear

public void clear()
Specified by:
clear in interface Map<K,V>

keySet

public Set<K> keySet()
Specified by:
keySet in interface Map<K,V>

values

public Collection<V> values()
Specified by:
values in interface Map<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()
Specified by:
entrySet in interface Map<K,V>

rehash

public void rehash()

clone

public FastMap<K,V> clone()
Overrides:
clone in class Object

hashCode

public int hashCode()
Specified by:
hashCode in interface Map<K,V>
Overrides:
hashCode in class Object

equals

public boolean equals(Object other)
Specified by:
equals in interface Map<K,V>
Overrides:
equals in class Object

toString

public String toString()
Overrides:
toString in class Object


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