org.apache.commons.collections

## Class FastTreeMap

- java.lang.Object
- - java.util.AbstractMap
  - - 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:
    Serialized Form

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class java.util.AbstractMap

      `AbstractMap.SimpleEntry, AbstractMap.SimpleImmutableEntry`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected boolean` | `fast` Are we operating in "fast" mode?
    `protected TreeMap` | `map` The underlying map we are managing.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `FastTreeMap()` Construct a an empty map.
    `FastTreeMap(Comparator comparator)` Construct an empty map with the specified comparator.
    `FastTreeMap(Map map)` Construct a new map with the same mappings as the specified map, sorted according to the keys's natural order
    `FastTreeMap(SortedMap map)` Construct a new map with the same mappings as the specified map, sorted according to the same ordering

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `clear()` Remove all mappings from this map.
    `Object` | `clone()` Return a shallow copy of this `FastTreeMap` instance.
    `Comparator` | `comparator()` Return the comparator used to order this map, or `null` if this map uses its keys' natural order.
    `boolean` | `containsKey(Object key)` Return `true` if this map contains a mapping for the specified key.
    `boolean` | `containsValue(Object value)` Return `true` if this map contains one or more keys mapping to the specified value.
    `Set` | `entrySet()` Return a collection view of the mappings contained in this map.
    `boolean` | `equals(Object o)` Compare the specified object with this list for equality.
    `Object` | `firstKey()` Return the first (lowest) key currently in this sorted map.
    `Object` | `get(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.
    `SortedMap` | `headMap(Object key)` Return a view of the portion of this map whose keys are strictly less than the specified key.
    `boolean` | `isEmpty()` Return `true` if this map contains no mappings.
    `Set` | `keySet()` Return a set view of the keys contained in this map.
    `Object` | `lastKey()` Return the last (highest) key currently in this sorted map.
    `Object` | `put(Object key, Object value)` Associate the specified value with the specified key in this map.
    `void` | `putAll(Map in)` Copy all of the mappings from the specified map to this one, replacing any mappings with the same keys.
    `Object` | `remove(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.
    `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).
    `SortedMap` | `tailMap(Object key)` Return a view of the portion of this map whose keys are greater than or equal to the specified key.
    `Collection` | `values()` Return a collection view of the values contained in this map.

    - ### Methods inherited from class java.util.TreeMap

      `ceilingEntry, ceilingKey, descendingKeySet, descendingMap, firstEntry, floorEntry, floorKey, headMap, higherEntry, higherKey, lastEntry, lowerEntry, lowerKey, navigableKeySet, pollFirstEntry, pollLastEntry, subMap, tailMap`

    - ### Methods inherited from class java.util.AbstractMap

      `toString`

    - ### Methods inherited from class java.lang.Object

      `finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### map

          protected TreeMap map

      The underlying map we are managing.

    - #### fast

          protected boolean fast

      Are we operating in "fast" mode?

  - ### Constructor Detail

    - #### 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 Detail

    - #### 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`

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