org.apache.commons.collections.map
public class SingletonMap extends Object implements OrderedMap, BoundedMap, KeyValue, Serializable, Cloneable
Map
implementation that holds a single item and is fixed size.
The single key/value pair is specified at creation.
The map is fixed size so any action that would change the size is disallowed.
However, the put
or setValue
methods can change
the value associated with the key.
If trying to remove or clear the map, an UnsupportedOperationException is thrown. If trying to put a new mapping into the map, an IllegalArgumentException is thrown. The put method will only suceed if the key specified is the same as the singleton key.
The key and value can be obtained by:
MapIterator
, see mapIterator
KeyValue
interface (just cast - no object creation)
Since: Commons Collections 3.1
Version: $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $
Constructor Summary | |
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SingletonMap()
Constructor that creates a map of null to null . | |
SingletonMap(Object key, Object value)
Constructor specifying the key and value.
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SingletonMap(KeyValue keyValue)
Constructor specifying the key and value as a KeyValue .
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SingletonMap(Entry mapEntry)
Constructor specifying the key and value as a MapEntry .
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SingletonMap(Map map)
Constructor copying elements from another map.
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Method Summary | |
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void | clear()
Unsupported operation. |
Object | clone()
Clones the map without cloning the key or value.
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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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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 | firstKey()
Gets the first (and only) key in the map.
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Object | get(Object key)
Gets the value mapped to the key specified.
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Object | getKey()
Gets the key.
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Object | getValue()
Gets the value.
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int | hashCode()
Gets the standard Map hashCode.
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boolean | isEmpty()
Checks whether the map is currently empty, which it never is.
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protected boolean | isEqualKey(Object key)
Compares the specified key to the stored key.
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protected boolean | isEqualValue(Object value)
Compares the specified value to the stored value.
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boolean | isFull()
Is the map currently full, always true.
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Set | keySet()
Gets the unmodifiable keySet view of the map.
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Object | lastKey()
Gets the last (and only) key in the map.
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MapIterator | mapIterator()
Gets an iterator over the map.
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int | maxSize()
Gets the maximum size of the map, always 1.
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Object | nextKey(Object key)
Gets the next key after the key specified, always null.
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OrderedMapIterator | orderedMapIterator()
Obtains an OrderedMapIterator over the map.
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Object | previousKey(Object key)
Gets the previous key before the key specified, always null.
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Object | put(Object key, Object value)
Puts a key-value mapping into this map where the key must match the existing key.
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void | putAll(Map map)
Puts the values from the specified map into this map.
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Object | remove(Object key)
Unsupported operation.
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Object | setValue(Object value)
Sets the value.
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int | size()
Gets the size of the map, always 1.
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String | toString()
Gets the map as a String.
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Collection | values()
Gets the unmodifiable values view of the map.
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null
to null
.Parameters: key the key to use value the value to use
KeyValue
.
Parameters: keyValue the key value pair to use
MapEntry
.
Parameters: mapEntry the mapEntry to use
Parameters: map the map to copy, must be size 1
Throws: NullPointerException if the map is null IllegalArgumentException if the size is not 1
Returns: a shallow clone
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
setValue
affect this map.
To simply iterate through the entries, use mapIterator.
Returns: the entrySet view
Parameters: obj the object to compare to
Returns: true if equal
Returns: the key
Parameters: key the key
Returns: the mapped value, null if no match
Returns: the key
Returns: the value
Returns: the hash code defined in the Map interface
Returns: false always
Parameters: key the key to compare
Returns: true if equal
Parameters: value the value to compare
Returns: true if equal
Returns: true always
Returns: the keySet view
Returns: the key
setValue
affect this map.
The remove
method is unsupported.
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
Returns: 1 always
Parameters: key the next key
Returns: null always
OrderedMapIterator
over the map.
A ordered map iterator is an efficient way of iterating over maps in both directions.
Returns: an ordered map iterator
Parameters: key the next key
Returns: null always
An IllegalArgumentException is thrown if the key does not match as the map is fixed size.
Parameters: key the key to set, must be the key of the map value the value to set
Returns: the value previously mapped to this key, null if none
Throws: IllegalArgumentException if the key does not match
The map must be of size 0 or size 1. If it is size 1, the key must match the key of this map otherwise an IllegalArgumentException is thrown.
Parameters: map the map to add, must be size 0 or 1, and the key must match
Throws: NullPointerException if the map is null IllegalArgumentException if the key does not match
Parameters: key the mapping to remove
Returns: the value mapped to the removed key, null if key not in map
Throws: UnsupportedOperationException always
Parameters: value the new value to set
Returns: the old value
Returns: the size of 1
Returns: a string version of the map
Returns: the values view