org.apache.commons.collections.map
public class Flat3Map extends Object implements IterableMap, Serializable, Cloneable
Map
implementation that stores data in simple fields until
the size is greater than 3.
This map is designed for performance and can outstrip HashMap. It also has good garbage collection characteristics.
The performance gains on puts are due to not needing to create a Map Entry object. This is a large saving not only in performance but in garbage collection.
Whilst in flat mode this map is also easy for the garbage collector to dispatch. This is because it contains no complex objects or arrays which slow the progress.
Do not use Flat3Map
if the size is likely to grow beyond 3.
Note that Flat3Map is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using java.util.Collections#synchronizedMap(Map). This class may throw exceptions when accessed by concurrent threads without synchronization.
Since: Commons Collections 3.0
Version: $Revision: 348007 $ $Date: 2005-11-21 22:52:57 +0000 (Mon, 21 Nov 2005) $
Constructor Summary | |
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Flat3Map()
Constructor. | |
Flat3Map(Map map)
Constructor copying elements from another map.
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Method Summary | |
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void | clear()
Clears the map, resetting the size to zero and nullifying references
to avoid garbage collection issues. |
Object | clone()
Clones the map without cloning the keys or values.
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boolean | containsKey(Object key)
Checks whether the map contains the specified key.
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boolean | containsValue(Object value)
Checks whether the map contains the specified value.
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protected AbstractHashedMap | createDelegateMap()
Create an instance of the map used for storage when in delegation mode.
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Set | entrySet()
Gets the entrySet view of the map.
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boolean | equals(Object obj)
Compares this map with another.
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Object | get(Object key)
Gets the value mapped to the key specified.
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int | hashCode()
Gets the standard Map hashCode.
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boolean | isEmpty()
Checks whether the map is currently empty.
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Set | keySet()
Gets the keySet view of the map.
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MapIterator | mapIterator()
Gets an iterator over the map.
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Object | put(Object key, Object value)
Puts a key-value mapping into this map.
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void | putAll(Map map)
Puts all the values from the specified map into this map.
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Object | remove(Object key)
Removes the specified mapping from this map.
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int | size()
Gets the size of the map.
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String | toString()
Gets the map as a String.
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Collection | values()
Gets the values view of the map.
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Parameters: map the map to copy
Throws: NullPointerException if the map is null
Returns: a shallow clone
Since: Commons Collections 3.1
Parameters: key the key to search for
Returns: true if the map contains the key
Parameters: value the value to search for
Returns: true if the map contains the key
This can be overridden by subclasses to provide a different map implementation. Not every AbstractHashedMap is suitable, identity and reference based maps would be poor choices.
Returns: a new AbstractHashedMap or subclass
Since: Commons Collections 3.1
Returns: the entrySet view
Parameters: obj the object to compare to
Returns: true if equal
Parameters: key the key
Returns: the mapped value, null if no match
Returns: the hash code defined in the Map interface
Returns: true if the map is currently size zero
Returns: the keySet view
A MapIterator returns the keys in the map. It also provides convenient methods to get the key and value, and set the value. It avoids the need to create an entrySet/keySet/values object. It also avoids creating the Map Entry object.
Returns: the map iterator
Parameters: key the key to add value the value to add
Returns: the value previously mapped to this key, null if none
Parameters: map the map to add
Throws: NullPointerException if the map is null
Parameters: key the mapping to remove
Returns: the value mapped to the removed key, null if key not in map
Returns: the size
Returns: a string version of the map
Returns: the values view