Package org.apache.commons.collections

Class FastTreeMap

java.lang.Object
java.util.AbstractMap<K,V>
java.util.TreeMap
org.apache.commons.collections.FastTreeMap
All Implemented Interfaces:
Serializable, Cloneable, Map, NavigableMap, SortedMap
public class FastTreeMap extends 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:

  • Clone the existing collection
  • Perform the modification on the clone
  • Replace the existing collection with the (modified) clone

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 Declaration.

Since:
Commons Collections 1.0
Version:
$Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
Author:
Craig R. McClanahan, Stephen Colebourne
See Also:

  • Field Details

    • map

      protected TreeMap map
      The underlying map we are managing.

    • fast

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

  • Constructor Details

    • FastTreeMap

      public FastTreeMap()
      Construct a an empty map.

    • FastTreeMap

      public FastTreeMap(Comparator comparator)
      Construct an empty map with the specified comparator.
      Parameters:
      comparator - the comparator to use for ordering tree elements

    • FastTreeMap

      public FastTreeMap(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(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 Details

    • getFast

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

    • 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

    • get

      public Object get(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.
      Specified by:
      get in interface Map
      Overrides:
      get in class TreeMap
      Parameters:
      key - the key whose value is to be returned
      Returns:
      the value mapped to that key, or null

    • size

      public int size()
      Return the number of key-value mappings in this map.
      Specified by:
      size in interface Map
      Overrides:
      size in class TreeMap
      Returns:
      the current size of the map

    • isEmpty

      public boolean isEmpty()
      Return true if this map contains no mappings.
      Specified by:
      isEmpty in interface Map
      Overrides:
      isEmpty in class AbstractMap
      Returns:
      is the map currently empty

    • containsKey

      public boolean containsKey(Object key)
      Return true if this map contains a mapping for the specified key.
      Specified by:
      containsKey in interface Map
      Overrides:
      containsKey in class TreeMap
      Parameters:
      key - the key to be searched for
      Returns:
      true if the map contains the key

    • containsValue

      public boolean containsValue(Object value)
      Return true if this map contains one or more keys mapping to the specified value.
      Specified by:
      containsValue in interface Map
      Overrides:
      containsValue in class TreeMap
      Parameters:
      value - the value to be searched for
      Returns:
      true if the map contains the value

    • comparator

      public Comparator comparator()
      Return the comparator used to order this map, or null if this map uses its keys' natural order.
      Specified by:
      comparator in interface SortedMap
      Overrides:
      comparator in class TreeMap
      Returns:
      the comparator used to order the map, or null if natural order

    • firstKey

      public Object firstKey()
      Return the first (lowest) key currently in this sorted map.
      Specified by:
      firstKey in interface SortedMap
      Overrides:
      firstKey in class TreeMap
      Returns:
      the first key in the map

    • lastKey

      public Object lastKey()
      Return the last (highest) key currently in this sorted map.
      Specified by:
      lastKey in interface SortedMap
      Overrides:
      lastKey in class TreeMap
      Returns:
      the last key in the map

    • put

      public Object put(Object key, 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.
      Specified by:
      put in interface Map
      Overrides:
      put in class TreeMap
      Parameters:
      key - the key with which the value is to be associated
      value - the value to be associated with this key
      Returns:
      the value previously mapped to the key, or null

    • putAll

      public void putAll(Map in)
      Copy all of the mappings from the specified map to this one, replacing any mappings with the same keys.
      Specified by:
      putAll in interface Map
      Overrides:
      putAll in class TreeMap
      Parameters:
      in - the map whose mappings are to be copied

    • remove

      public Object remove(Object key)
      Remove any mapping for this key, and return any previously mapped value.
      Specified by:
      remove in interface Map
      Overrides:
      remove in class TreeMap
      Parameters:
      key - the key whose mapping is to be removed
      Returns:
      the value removed, or null

    • clear

      public void clear()
      Remove all mappings from this map.
      Specified by:
      clear in interface Map
      Overrides:
      clear in class TreeMap

    • equals

      public boolean equals(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.
      Specified by:
      equals in interface Map
      Overrides:
      equals in class AbstractMap
      Parameters:
      o - the object to be compared to this list
      Returns:
      true if the two maps are equal

    • 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.
      Specified by:
      hashCode in interface Map
      Overrides:
      hashCode in class AbstractMap
      Returns:
      a suitable integer hash code

    • clone

      public Object clone()
      Return a shallow copy of this FastTreeMap instance. The keys and values themselves are not copied.
      Overrides:
      clone in class TreeMap
      Returns:
      a clone of this map

    • headMap

      public SortedMap headMap(Object key)
      Return a view of the portion of this map whose keys are strictly less than the specified key.
      Specified by:
      headMap in interface NavigableMap
      Specified by:
      headMap in interface SortedMap
      Overrides:
      headMap in class TreeMap
      Parameters:
      key - Key higher than any in the returned map
      Returns:
      a head map

    • subMap

      public SortedMap subMap(Object fromKey, Object toKey)
      Return a view of the portion of this map whose keys are in the range fromKey (inclusive) to toKey (exclusive).
      Specified by:
      subMap in interface NavigableMap
      Specified by:
      subMap in interface SortedMap
      Overrides:
      subMap in class TreeMap
      Parameters:
      fromKey - Lower limit of keys for the returned map
      toKey - Upper limit of keys for the returned map
      Returns:
      a sub map

    • tailMap

      public SortedMap tailMap(Object key)
      Return a view of the portion of this map whose keys are greater than or equal to the specified key.
      Specified by:
      tailMap in interface NavigableMap
      Specified by:
      tailMap in interface SortedMap
      Overrides:
      tailMap in class TreeMap
      Parameters:
      key - Key less than or equal to any in the returned map
      Returns:
      a tail map

    • entrySet

      public Set entrySet()
      Return a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry.
      Specified by:
      entrySet in interface Map
      Specified by:
      entrySet in interface SortedMap
      Overrides:
      entrySet in class TreeMap

    • keySet

      public Set keySet()
      Return a set view of the keys contained in this map.
      Specified by:
      keySet in interface Map
      Specified by:
      keySet in interface SortedMap
      Overrides:
      keySet in class TreeMap

    • values

      public Collection values()
      Return a collection view of the values contained in this map.
      Specified by:
      values in interface Map
      Specified by:
      values in interface SortedMap
      Overrides:
      values in class TreeMap