java.lang.Object | |||
↳ | java.util.AbstractMap <K, V> | ||
↳ | java.util.HashMap <K, V> | ||
↳ | java.util.LinkedHashMap<K, V> |
LinkedHashMap is an implementation of
Map
that guarantees iteration order.
All optional operations are supported.
All elements are permitted as keys or values, including null.
Entries are kept in a doubly-linked list. The iteration order is, by default, the
order in which keys were inserted. Reinserting an already-present key doesn't change the
order. If the three argument constructor is used, and
accessOrder
is specified as
true
, the iteration will be in the order that entries were accessed.
The access order is affected by
put
,
get
, and
putAll
operations,
but not by operations on the collection views.
Note: the implementation of
LinkedHashMap
is not synchronized.
If one thread of several threads accessing an instance modifies the map
structurally, access to the map needs to be synchronized. For
insertion-ordered instances a structural modification is an operation that
removes or adds an entry. Access-ordered instances also are structurally
modified by
put
,
get
, and
putAll
since these methods
change the order of the entries. Changes in the value of an entry are not structural changes.
The
Iterator
created by calling the
iterator
method
may throw a
ConcurrentModificationException
if the map is structurally
changed while an iterator is used to iterate over the elements. Only the
remove
method that is provided by the iterator allows for removal of
elements during iteration. It is not possible to guarantee that this
mechanism works in all cases of unsynchronized concurrent modification. It
should only be used for debugging purposes.
Public Constructors | |||||||||||
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Constructs a new empty
LinkedHashMap
instance.
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Constructs a new
LinkedHashMap
instance with the specified
capacity.
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Constructs a new
LinkedHashMap
instance with the specified
capacity and load factor.
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Constructs a new
LinkedHashMap
instance with the specified
capacity, load factor and a flag specifying the ordering behavior.
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Constructs a new
LinkedHashMap
instance containing the mappings
from the specified map.
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Public Methods | |||||||||||
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Removes all mappings from this hash map, leaving it empty.
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This override is done for LinkedHashMap performance: iteration is cheaper
via LinkedHashMap nxt links.
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Returns the value of the mapping with the specified key.
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Protected Methods | |||||||||||
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[Expand]
Inherited Methods
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From class
java.util.HashMap
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From class
java.util.AbstractMap
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From class
java.lang.Object
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From interface
java.util.Map
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Constructs a new
LinkedHashMap
instance with the specified
capacity.
initialCapacity | the initial capacity of this map. |
---|
IllegalArgumentException | when the capacity is less than zero. |
---|
Constructs a new
LinkedHashMap
instance with the specified
capacity and load factor.
initialCapacity | the initial capacity of this map. |
---|---|
loadFactor | the initial load factor. |
IllegalArgumentException | when the capacity is less than zero or the load factor is less or equal to zero. |
---|
Constructs a new
LinkedHashMap
instance with the specified
capacity, load factor and a flag specifying the ordering behavior.
initialCapacity | the initial capacity of this hash map. |
---|---|
loadFactor | the initial load factor. |
accessOrder |
true
if the ordering should be done based on the last
access (from least-recently accessed to most-recently
accessed), and
false
if the ordering should be the
order in which the entries were inserted.
|
IllegalArgumentException | when the capacity is less than zero or the load factor is less or equal to zero. |
---|
Constructs a new
LinkedHashMap
instance containing the mappings
from the specified map. The order of the elements is preserved.
map | the mappings to add. |
---|
Removes all mappings from this hash map, leaving it empty.
This override is done for LinkedHashMap performance: iteration is cheaper via LinkedHashMap nxt links.
value | the value to search for. |
---|
true
if this map contains the specified value,
false
otherwise.
Returns the value of the mapping with the specified key.
key | the key. |
---|
null
if no mapping for the specified key is found.