Class IdentityMap
- java.lang.Object
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- java.util.AbstractMap
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- org.apache.commons.collections.map.AbstractHashedMap
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- org.apache.commons.collections.map.IdentityMap
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- All Implemented Interfaces:
java.io.Serializable
,java.lang.Cloneable
,java.util.Map
,IterableMap
public class IdentityMap extends AbstractHashedMap implements java.io.Serializable, java.lang.Cloneable
AMap
implementation that matches keys and values based on==
notequals()
.This map will violate the detail of various Map and map view contracts. As a general rule, don't compare this map to other maps.
Note that IdentityMap 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
Collections.synchronizedMap(Map)
. This class may throw exceptions when accessed by concurrent threads without synchronization.- Since:
- Commons Collections 3.0
- Version:
- $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
- See Also:
- Serialized Form
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Nested Class Summary
Nested Classes Modifier and Type Class Description protected static class
IdentityMap.IdentityEntry
HashEntry-
Nested classes/interfaces inherited from class org.apache.commons.collections.map.AbstractHashedMap
AbstractHashedMap.EntrySet, AbstractHashedMap.EntrySetIterator, AbstractHashedMap.HashEntry, AbstractHashedMap.HashIterator, AbstractHashedMap.HashMapIterator, AbstractHashedMap.KeySet, AbstractHashedMap.KeySetIterator, AbstractHashedMap.Values, AbstractHashedMap.ValuesIterator
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Field Summary
Fields Modifier and Type Field Description private static long
serialVersionUID
Serialisation version-
Fields inherited from class org.apache.commons.collections.map.AbstractHashedMap
data, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD, entrySet, GETKEY_INVALID, GETVALUE_INVALID, keySet, loadFactor, MAXIMUM_CAPACITY, modCount, NO_NEXT_ENTRY, NO_PREVIOUS_ENTRY, NULL, REMOVE_INVALID, SETVALUE_INVALID, size, threshold, values
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Constructor Summary
Constructors Constructor Description IdentityMap()
Constructs a new empty map with default size and load factor.IdentityMap(int initialCapacity)
Constructs a new, empty map with the specified initial capacity.IdentityMap(int initialCapacity, float loadFactor)
Constructs a new, empty map with the specified initial capacity and load factor.IdentityMap(java.util.Map map)
Constructor copying elements from another map.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Object
clone()
Clones the map without cloning the keys or values.protected AbstractHashedMap.HashEntry
createEntry(AbstractHashedMap.HashEntry next, int hashCode, java.lang.Object key, java.lang.Object value)
Creates an entry to store the data.protected int
hash(java.lang.Object key)
Gets the hash code for the key specified.protected boolean
isEqualKey(java.lang.Object key1, java.lang.Object key2)
Compares two keys for equals.protected boolean
isEqualValue(java.lang.Object value1, java.lang.Object value2)
Compares two values for equals.private void
readObject(java.io.ObjectInputStream in)
Read the map in using a custom routine.private void
writeObject(java.io.ObjectOutputStream out)
Write the map out using a custom routine.-
Methods inherited from class org.apache.commons.collections.map.AbstractHashedMap
addEntry, addMapping, calculateNewCapacity, calculateThreshold, checkCapacity, clear, containsKey, containsValue, convertKey, createEntrySetIterator, createKeySetIterator, createValuesIterator, destroyEntry, doReadObject, doWriteObject, ensureCapacity, entryHashCode, entryKey, entryNext, entrySet, entryValue, equals, get, getEntry, hashCode, hashIndex, init, isEmpty, keySet, mapIterator, put, putAll, remove, removeEntry, removeMapping, reuseEntry, size, toString, updateEntry, values
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Field Detail
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serialVersionUID
private static final long serialVersionUID
Serialisation version- See Also:
- Constant Field Values
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Constructor Detail
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IdentityMap
public IdentityMap()
Constructs a new empty map with default size and load factor.
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IdentityMap
public IdentityMap(int initialCapacity)
Constructs a new, empty map with the specified initial capacity.- Parameters:
initialCapacity
- the initial capacity- Throws:
java.lang.IllegalArgumentException
- if the initial capacity is less than one
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IdentityMap
public IdentityMap(int initialCapacity, float loadFactor)
Constructs a new, empty map with the specified initial capacity and load factor.- Parameters:
initialCapacity
- the initial capacityloadFactor
- the load factor- Throws:
java.lang.IllegalArgumentException
- if the initial capacity is less than onejava.lang.IllegalArgumentException
- if the load factor is less than zero
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IdentityMap
public IdentityMap(java.util.Map map)
Constructor copying elements from another map.- Parameters:
map
- the map to copy- Throws:
java.lang.NullPointerException
- if the map is null
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Method Detail
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hash
protected int hash(java.lang.Object key)
Gets the hash code for the key specified. This implementation uses the identity hash code.- Overrides:
hash
in classAbstractHashedMap
- Parameters:
key
- the key to get a hash code for- Returns:
- the hash code
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isEqualKey
protected boolean isEqualKey(java.lang.Object key1, java.lang.Object key2)
Compares two keys for equals. This implementation uses==
.- Overrides:
isEqualKey
in classAbstractHashedMap
- Parameters:
key1
- the first key to comparekey2
- the second key to compare- Returns:
- true if equal by identity
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isEqualValue
protected boolean isEqualValue(java.lang.Object value1, java.lang.Object value2)
Compares two values for equals. This implementation uses==
.- Overrides:
isEqualValue
in classAbstractHashedMap
- Parameters:
value1
- the first value to comparevalue2
- the second value to compare- Returns:
- true if equal by identity
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createEntry
protected AbstractHashedMap.HashEntry createEntry(AbstractHashedMap.HashEntry next, int hashCode, java.lang.Object key, java.lang.Object value)
Creates an entry to store the data. This implementation creates an IdentityEntry instance.- Overrides:
createEntry
in classAbstractHashedMap
- Parameters:
next
- the next entry in sequencehashCode
- the hash code to usekey
- the key to storevalue
- the value to store- Returns:
- the newly created entry
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clone
public java.lang.Object clone()
Clones the map without cloning the keys or values.- Overrides:
clone
in classAbstractHashedMap
- Returns:
- a shallow clone
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writeObject
private void writeObject(java.io.ObjectOutputStream out) throws java.io.IOException
Write the map out using a custom routine.- Throws:
java.io.IOException
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readObject
private void readObject(java.io.ObjectInputStream in) throws java.io.IOException, java.lang.ClassNotFoundException
Read the map in using a custom routine.- Throws:
java.io.IOException
java.lang.ClassNotFoundException
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