org.apache.commons.collections
Class FastTreeMap

java.lang.Object
  extended byjava.util.AbstractMap
      extended byjava.util.TreeMap
          extended byorg.apache.commons.collections.FastTreeMap
All Implemented Interfaces:
java.lang.Cloneable, java.util.Map, java.io.Serializable, java.util.SortedMap

public class FastTreeMap
extends java.util.TreeMap

A customized implementation of java.util.TreeMap designed to operate in a multithreaded environment where the large majority of method calls are read-only, instead of structural changes. When operating in "fast" mode, read calls are non-synchronized and write calls perform the following steps:

When first created, objects of this class default to "slow" mode, where all accesses of any type are synchronized but no cloning takes place. This is appropriate for initially populating the collection, followed by a switch to "fast" mode (by calling setFast(true)) after initialization is complete.

NOTE: If you are creating and accessing a TreeMap only within a single thread, you should use java.util.TreeMap directly (with no synchronization), for maximum performance.

NOTE: This class is not cross-platform. Using it may cause unexpected failures on some architectures. It suffers from the same problems as the double-checked locking idiom. In particular, the instruction that clones the internal collection and the instruction that sets the internal reference to the clone can be executed or perceived out-of-order. This means that any read operation might fail unexpectedly, as it may be reading the state of the internal collection before the internal collection is fully formed. For more information on the double-checked locking idiom, see the Double-Checked Locking Idiom Is Broken Declartion.

Since:
1.0
Version:
$Revision: 1.10 $ $Date: 2002/10/12 22:15:18 $
Author:
Craig R. McClanahan
See Also:
Serialized Form

Field Summary
protected  boolean fast
          Are we operating in "fast" mode?
protected  java.util.TreeMap map
          The underlying map we are managing.
 
Constructor Summary
FastTreeMap()
          Construct a an empty map.
FastTreeMap(java.util.Comparator comparator)
          Construct an empty map with the specified comparator.
FastTreeMap(java.util.Map map)
          Construct a new map with the same mappings as the specified map, sorted according to the keys's natural order
FastTreeMap(java.util.SortedMap map)
          Construct a new map with the same mappings as the specified map, sorted according to the same ordering
 
Method Summary
 void clear()
          Remove all mappings from this map.
 java.lang.Object clone()
          Return a shallow copy of this FastTreeMap instance.
 java.util.Comparator comparator()
          Return the comparator used to order this map, or null if this map uses its keys' natural order.
 boolean containsKey(java.lang.Object key)
          Return true if this map contains a mapping for the specified key.
 boolean containsValue(java.lang.Object value)
          Return true if this map contains one or more keys mapping to the specified value.
 java.util.Set entrySet()
          Return a collection view of the mappings contained in this map.
 boolean equals(java.lang.Object o)
          Compare the specified object with this list for equality.
 java.lang.Object firstKey()
          Return the first (lowest) key currently in this sorted map.
 java.lang.Object get(java.lang.Object key)
          Return the value to which this map maps the specified key.
 boolean getFast()
          Returns true if this map is operating in fast mode.
 int hashCode()
          Return the hash code value for this map.
 java.util.SortedMap headMap(java.lang.Object key)
          Return a view of the portion of this map whose keys are strictly less than the specified key.
 boolean isEmpty()
          Test if this list has no elements.
 java.util.Set keySet()
          Return a set view of the keys contained in this map.
 java.lang.Object lastKey()
          Return the last (highest) key currently in this sorted map.
 java.lang.Object put(java.lang.Object key, java.lang.Object value)
          Associate the specified value with the specified key in this map.
 void putAll(java.util.Map in)
          Copy all of the mappings from the specified map to this one, replacing any mappings with the same keys.
 java.lang.Object remove(java.lang.Object key)
          Remove any mapping for this key, and return any previously mapped value.
 void setFast(boolean fast)
          Sets whether this map is operating in fast mode.
 int size()
          Return the number of key-value mappings in this map.
 java.util.SortedMap subMap(java.lang.Object fromKey, java.lang.Object toKey)
          Return a view of the portion of this map whose keys are in the range fromKey (inclusive) to toKey (exclusive).
 java.util.SortedMap tailMap(java.lang.Object key)
          Return a view of the portion of this map whose keys are greater than or equal to the specified key.
 java.util.Collection values()
          Return a collection view of the values contained in this map.
 
Methods inherited from class java.util.AbstractMap
toString
 
Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

fast

protected boolean fast
Are we operating in "fast" mode?


map

protected java.util.TreeMap map
The underlying map we are managing.

Constructor Detail

FastTreeMap

public FastTreeMap()
Construct a an empty map.


FastTreeMap

public FastTreeMap(java.util.Comparator comparator)
Construct an empty map with the specified comparator.

Parameters:
comparator - The comparator to use for ordering tree elements

FastTreeMap

public FastTreeMap(java.util.Map map)
Construct a new map with the same mappings as the specified map, sorted according to the keys's natural order

Parameters:
map - The map whose mappings are to be copied

FastTreeMap

public FastTreeMap(java.util.SortedMap map)
Construct a new map with the same mappings as the specified map, sorted according to the same ordering

Parameters:
map - The map whose mappings are to be copied
Method Detail

clear

public void clear()
Remove all mappings from this map.


clone

public java.lang.Object clone()
Return a shallow copy of this FastTreeMap instance. The keys and values themselves are not copied.


comparator

public java.util.Comparator comparator()
Return the comparator used to order this map, or null if this map uses its keys' natural order.


containsKey

public boolean containsKey(java.lang.Object key)
Return true if this map contains a mapping for the specified key.

Parameters:
key - Key to be searched for

containsValue

public boolean containsValue(java.lang.Object value)
Return true if this map contains one or more keys mapping to the specified value.

Parameters:
value - Value to be searched for

entrySet

public java.util.Set entrySet()
Return a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry.


equals

public boolean equals(java.lang.Object o)
Compare the specified object with this list for equality. This implementation uses exactly the code that is used to define the list equals function in the documentation for the Map.equals method.

Parameters:
o - Object to be compared to this list

firstKey

public java.lang.Object firstKey()
Return the first (lowest) key currently in this sorted map.


get

public java.lang.Object get(java.lang.Object key)
Return the value to which this map maps the specified key. Returns null if the map contains no mapping for this key, or if there is a mapping with a value of null. Use the containsKey() method to disambiguate these cases.

Parameters:
key - Key whose value is to be returned

getFast

public boolean getFast()
Returns true if this map is operating in fast mode.

Returns:
true if this map is operating in fast mode

hashCode

public int hashCode()
Return the hash code value for this map. This implementation uses exactly the code that is used to define the list hash function in the documentation for the Map.hashCode method.


headMap

public java.util.SortedMap headMap(java.lang.Object key)
Return a view of the portion of this map whose keys are strictly less than the specified key.

Parameters:
key - Key higher than any in the returned map

isEmpty

public boolean isEmpty()
Test if this list has no elements.


keySet

public java.util.Set keySet()
Return a set view of the keys contained in this map.


lastKey

public java.lang.Object lastKey()
Return the last (highest) key currently in this sorted map.


put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object value)
Associate the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced and returned.

Parameters:
key - The key with which the value is to be associated
value - The value to be associated with this key

putAll

public void putAll(java.util.Map in)
Copy all of the mappings from the specified map to this one, replacing any mappings with the same keys.

Parameters:
in - Map whose mappings are to be copied

remove

public java.lang.Object remove(java.lang.Object key)
Remove any mapping for this key, and return any previously mapped value.

Parameters:
key - Key whose mapping is to be removed

setFast

public void setFast(boolean fast)
Sets whether this map is operating in fast mode.

Parameters:
fast - true if this map should operate in fast mode

size

public int size()
Return the number of key-value mappings in this map.


subMap

public java.util.SortedMap subMap(java.lang.Object fromKey,
                                  java.lang.Object toKey)
Return a view of the portion of this map whose keys are in the range fromKey (inclusive) to toKey (exclusive).

Parameters:
fromKey - Lower limit of keys for the returned map
toKey - Upper limit of keys for the returned map

tailMap

public java.util.SortedMap tailMap(java.lang.Object key)
Return a view of the portion of this map whose keys are greater than or equal to the specified key.

Parameters:
key - Key less than or equal to any in the returned map

values

public java.util.Collection values()
Return a collection view of the values contained in this map.



Copyright © 2001-2002 Apache Software Foundation. Documenation generated July 6 2004.