java.lang.Object
- java.util.AbstractMap
- - freemarker.ext.util.IdentityHashMap

All Implemented Interfaces:

Serializable, Cloneable, Map
```
public class IdentityHashMap
extends AbstractMap
implements Map, Cloneable, Serializable
```
A variant of HashMap that uses System.identityHashCode(Object) for hashing, and reference comparison instead of Object.equals(Object). Note that this applies only to keys, and not to values, i.e. containsValue(Object) still uses Object.equals(Object).

See Also:

Serialized Form

Nested Class Summary
- Nested classes/interfaces inherited from class java.util.AbstractMap
  AbstractMap.SimpleEntry<K extends Object,V extends Object>, AbstractMap.SimpleImmutableEntry<K extends Object,V extends Object>

Field Summary

Fields
Modifier and Type Field Description

static long serialVersionUID

Constructor Summary

Constructors
Constructor	Description
`IdentityHashMap()`	Constructs a new, empty map with a default capacity and load factor, which is `0.75`.
`IdentityHashMap(int initialCapacity)`	Constructs a new, empty map with the specified initial capacity and default load factor, which is `0.75`.
`IdentityHashMap(int initialCapacity, float loadFactor)`	Constructs a new, empty map with the specified initial capacity and the specified load factor.
`IdentityHashMap(Map t)`	Constructs a new map with the same mappings as the given map.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`clear()`	Removes all mappings from this map.
`Object`	`clone()`	Returns a shallow copy of this `IdentityHashMap` instance: the keys and values themselves are not cloned.
`boolean`	`containsKey(Object key)`	Returns `true` if this map contains a mapping for the specified key.
`boolean`	`containsValue(Object value)`	Returns `true` if this map maps one or more keys to the specified value.
`Set`	`entrySet()`	Returns a collection view of the mappings contained in this map.
`Object`	`get(Object key)`	Returns the value to which this map maps the specified key.
`boolean`	`isEmpty()`	Returns `true` if this map contains no key-value mappings.
`Set`	`keySet()`	Returns a set view of the keys contained in this map.
`Object`	`put(Object key, Object value)`	Associates the specified value with the specified key in this map.
`void`	`putAll(Map t)`	Copies all of the mappings from the specified map to this one.
`Object`	`remove(Object key)`	Removes the mapping for this key from this map if present.
`int`	`size()`	Returns the number of key-value mappings in this map.
`Collection`	`values()`	Returns a collection view of the values contained in this map.

Methods inherited from class java.util.AbstractMap
equals, hashCode, toString

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map
compute, computeIfAbsent, computeIfPresent, equals, forEach, getOrDefault, hashCode, merge, putIfAbsent, remove, replace, replace, replaceAll

- Field Detail
  - serialVersionUID
```
public static final long serialVersionUID
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - IdentityHashMap
```
public IdentityHashMap(int initialCapacity,
                       float loadFactor)
```
    Constructs a new, empty map with the specified initial capacity and the specified load factor.
    
    Parameters:
    
    initialCapacity - the initial capacity of the IdentityHashMap.
    
    loadFactor - the load factor of the IdentityHashMap
    
    Throws:
    
    IllegalArgumentException - if the initial capacity is less than zero, or if the load factor is nonpositive.
  - IdentityHashMap
```
public IdentityHashMap(int initialCapacity)
```
    Constructs a new, empty map with the specified initial capacity and default load factor, which is 0.75.
    
    Parameters:
    
    initialCapacity - the initial capacity of the IdentityHashMap.
    
    Throws:
    
    IllegalArgumentException - if the initial capacity is less than zero.
  - IdentityHashMap
```
public IdentityHashMap()
```
    Constructs a new, empty map with a default capacity and load factor, which is 0.75.
  - IdentityHashMap
```
public IdentityHashMap(Map t)
```
    Constructs a new map with the same mappings as the given map. The map is created with a capacity of twice the number of mappings in the given map or 11 (whichever is greater), and a default load factor, which is 0.75.
    
    Parameters:
    
    t - the map whose mappings are to be placed in this map.
- Method Detail
  - size
```
public int size()
```
    Returns the number of key-value mappings in this map.
    
    Specified by:
    
    size in interface Map
    
    Overrides:
    
    size in class AbstractMap
    
    Returns:
    
    the number of key-value mappings in this map.
  - isEmpty
```
public boolean isEmpty()
```
    Returns true if this map contains no key-value mappings.
    
    Specified by:
    
    isEmpty in interface Map
    
    Overrides:
    
    isEmpty in class AbstractMap
    
    Returns:
    
    true if this map contains no key-value mappings.
  - containsValue
```
public boolean containsValue(Object value)
```
    Returns true if this map maps one or more keys to the specified value.
    
    Specified by:
    
    containsValue in interface Map
    
    Overrides:
    
    containsValue in class AbstractMap
    
    Parameters:
    
    value - value whose presence in this map is to be tested.
    
    Returns:
    
    true if this map maps one or more keys to the specified value.
  - containsKey
```
public boolean containsKey(Object key)
```
    Returns true if this map contains a mapping for the specified key.
    
    Specified by:
    
    containsKey in interface Map
    
    Overrides:
    
    containsKey in class AbstractMap
    
    Parameters:
    
    key - key whose presence in this Map is to be tested.
    
    Returns:
    
    true if this map contains a mapping for the specified key.
  - get
```
public Object get(Object key)
```
    Returns the value to which this map maps the specified key. Returns null if the map contains no mapping for this key. A return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.
    
    Specified by:
    
    get in interface Map
    
    Overrides:
    
    get in class AbstractMap
    
    Parameters:
    
    key - key whose associated value is to be returned.
    
    Returns:
    
    the value to which this map maps the specified key.
  - put
```
public Object put(Object key,
                  Object value)
```
    Associates 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.
    
    Specified by:
    
    put in interface Map
    
    Overrides:
    
    put in class AbstractMap
    
    Parameters:
    
    key - key with which the specified value is to be associated.
    
    value - value to be associated with the specified key.
    
    Returns:
    
    previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the IdentityHashMap previously associated null with the specified key.
  - remove
```
public Object remove(Object key)
```
    Removes the mapping for this key from this map if present.
    
    Specified by:
    
    remove in interface Map
    
    Overrides:
    
    remove in class AbstractMap
    
    Parameters:
    
    key - key whose mapping is to be removed from the map.
    
    Returns:
    
    previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key.
  - putAll
```
public void putAll(Map t)
```
    Copies all of the mappings from the specified map to this one. These mappings replace any mappings that this map had for any of the keys currently in the specified Map.
    
    Specified by:
    
    putAll in interface Map
    
    Overrides:
    
    putAll in class AbstractMap
    
    Parameters:
    
    t - Mappings to be stored in this map.
  - clear
```
public void clear()
```
    Removes all mappings from this map.
    
    Specified by:
    
    clear in interface Map
    
    Overrides:
    
    clear in class AbstractMap
  - clone
```
public Object clone()
```
    Returns a shallow copy of this IdentityHashMap instance: the keys and values themselves are not cloned.
    
    Overrides:
    
    clone in class AbstractMap
    
    Returns:
    
    a shallow copy of this map.
  - keySet
```
public Set keySet()
```
    Returns a set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice versa. The set supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.
    
    Specified by:
    
    keySet in interface Map
    
    Overrides:
    
    keySet in class AbstractMap
    
    Returns:
    
    a set view of the keys contained in this map.
  - values
```
public Collection values()
```
    Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice versa. The collection supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.
    
    Specified by:
    
    values in interface Map
    
    Overrides:
    
    values in class AbstractMap
    
    Returns:
    
    a collection view of the values contained in this map.
  - entrySet
```
public Set entrySet()
```
    Returns a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry. The collection is backed by the map, so changes to the map are reflected in the collection, and vice versa. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.
    
    Specified by:
    
    entrySet in interface Map
    
    Specified by:
    
    entrySet in class AbstractMap
    
    Returns:
    
    a collection view of the mappings contained in this map.
    
    See Also:
    
    Map.Entry

Class IdentityHashMap

Nested Class Summary

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

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.util.AbstractMap

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Field Detail

serialVersionUID

Constructor Detail

IdentityHashMap

IdentityHashMap

IdentityHashMap

IdentityHashMap

Method Detail

size

isEmpty

containsValue

containsKey

get

put

remove

putAll

clear

clone

keySet

values

entrySet