| com.go.trove.util.IdentityMap
| IdentityMap | | public class IdentityMap extends AbstractMap implements Cloneable(Code) | | An IdentityMap is like WeakHashMap, except it uses a key's identity
hashcode and equals methods. IdentityMap is not thread-safe and must be
wrapped with Collections.synchronizedMap to be made thread-safe. Most of the
implementation for this class is ripped off from java.util.HashMap, but not
java.util.WeakHashMap, in order to acheive greater efficiency.
The documentation for WeakHashMap states that it is intended primarily
for use with key objects whose equals methods test for object identity
using the == operator. Because WeakHashMap uses a key's own equals and
hashcode methods, it is better suited for implementing methods that behave
like
String.intern . However, because WeakHashMap stongly references
values,
Utils.intern Utils.intern provides a safer intern mechanism.
In this implementation, all key objects are tested for equality using the
== operator, and null keys are not permitted. IdentityMap is therefore
better suited for "canonicalized" mappings.
Note: Weakly referenced entries may be automatically removed during
either accessor or mutator operations, possibly causing a concurrent
modification to be detected. Therefore, even if multiple threads are only
accessing this map, be sure to synchronize this map first. Also, do not
rely on the value returned by size() when using an iterator from this map.
The iterators may return less entries than the amount reported by size().
parametrized for GJ by Stefan Reich (doc@drjava.de)
author:
Brian S O'Neill
version:
, 00/12/18
See Also: java.util.WeakHashMap
See Also: java.util.HashMap |
| Constructor Summary | |
| public | IdentityMap(int initialCapacity, float loadFactor)
Constructs a new, empty map with the specified initial
capacity and the specified load factor. | | public | IdentityMap(int initialCapacity)
Constructs a new, empty map with the specified initial capacity
and default load factor, which is 0.75. | | public | IdentityMap()
Constructs a new, empty map with a default capacity and load
factor, which is 0.75. | | public | IdentityMap(Map t)
Constructs a new map with the same mappings as the given map. |
| Method Summary | |
| public void | clear()
Removes all mappings from this map. | | public Object | clone()
Returns a shallow copy of this HashMap instance: the keys and
values themselves are not cloned. | | public boolean | containsKey(A key)
Returns true if this map contains a mapping for the specified
key. | | public boolean | containsValue(B value)
Returns true if this map maps one or more keys to the
specified value.
Parameters:
value - value whose presence in this map is to be tested. | | public Set<Map.Entry<A, B>> | entrySet()
Returns a collection view of the mappings contained in this map. | | public B | get(A key)
Returns the value to which this map maps the specified key. | | public boolean | isEmpty()
Returns true if this map contains no key-value mappings. | | public Set<A> | keySet()
Returns a set view of the keys contained in this map. | | public B | put(A key, B 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.
Parameters:
key - key with which the specified value is to be associated.
Parameters:
value - value to be associated with the specified key. | | public void | putAll(Map<A, B> t)
Copies all of the mappings from the specified map to this one. | | public B | remove(A key)
Removes the mapping for this key from this map if present.
Parameters:
key - key whose mapping is to be removed from the map. | | public int | size()
Returns the number of key-value mappings in this map, but this value
may be larger than actual amount of entries produced by an iterator. | | static String | toString(Collection c)
Converts a string to a collection without calling size(). | | public String | toString()
| | public Collection<B> | values()
Returns a collection view of the values contained in this map. |
| ENTRIES | | final static int ENTRIES(Code) | | |
| KEYS | | final static int KEYS(Code) | | |
| VALUES | | final static int VALUES(Code) | | |
| IdentityMap | | public IdentityMap(int initialCapacity, float loadFactor)(Code) | | Constructs a new, empty map with the specified initial
capacity and the specified load factor.
Parameters:
initialCapacity - the initial capacity of the HashMap.
Parameters:
loadFactor - the load factor of the HashMap
throws:
IllegalArgumentException - if the initial capacity is lessthan zero, or if the load factor is nonpositive. |
| IdentityMap | | public IdentityMap(int initialCapacity)(Code) | | 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 HashMap.
throws:
IllegalArgumentException - if the initial capacity is lessthan zero. |
| IdentityMap | | public IdentityMap()(Code) | | Constructs a new, empty map with a default capacity and load
factor, which is 0.75.
|
| IdentityMap | | public IdentityMap(Map t)(Code) | | 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.
|
| clear | | public void clear()(Code) | | Removes all mappings from this map.
|
| clone | | public Object clone()(Code) | | Returns a shallow copy of this HashMap instance: the keys and
values themselves are not cloned.
a shallow copy of this map. |
| containsKey | | public boolean containsKey(A key)(Code) | | Returns true if this map contains a mapping for the specified
key.
true if this map contains a mapping for the specifiedkey.
Parameters:
key - key whose presence in this Map is to be tested. |
| containsValue | | public boolean containsValue(B value)(Code) | | Returns true if this map maps one or more keys to the
specified value.
Parameters:
value - value whose presence in this map is to be tested. true if this map maps one or more keys to thespecified value. |
| entrySet | | public Set<Map.Entry<A, B>> entrySet()(Code) | | 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.
a collection view of the mappings contained in this map.
See Also: Map.Entry |
| get | | public B get(A key)(Code) | | 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.
the value to which this map maps the specified key.
Parameters:
key - key whose associated value is to be returned. |
| isEmpty | | public boolean isEmpty()(Code) | | Returns true if this map contains no key-value mappings.
true if this map contains no key-value mappings. |
| keySet | | public Set<A> keySet()(Code) | | 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.
a set view of the keys contained in this map. |
| put | | public B put(A key, B value)(Code) | | 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.
Parameters:
key - key with which the specified value is to be associated.
Parameters:
value - value to be associated with the specified key. previous value associated with specified key, or nullif there was no mapping for key. A null return canalso indicate that the HashMap previously associatednull with the specified key. |
| putAll | | public void putAll(Map<A, B> t)(Code) | | 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.
Parameters:
t - Mappings to be stored in this map. |
| remove | | public B remove(A key)(Code) | | Removes the mapping for this key from this map if present.
Parameters:
key - key whose mapping is to be removed from the map. previous value associated with specified key, or nullif there was no mapping for key. A null return canalso indicate that the map previously associated nullwith the specified key. |
| size | | public int size()(Code) | | Returns the number of key-value mappings in this map, but this value
may be larger than actual amount of entries produced by an iterator.
the number of key-value mappings in this map. |
| toString | | static String toString(Collection c)(Code) | | Converts a string to a collection without calling size(). Iterators from
this map may return less entries than the amount reported by size().
|
| values | | public Collection<B> values()(Code) | | 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.
a collection view of the values contained in this map. |
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