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Added in API level 1

LinkedHashMap

public class LinkedHashMap
extends HashMap<K, V>

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.

Summary

Public constructors

LinkedHashMap()

Constructs a new empty LinkedHashMap instance.

LinkedHashMap(int initialCapacity)

Constructs a new LinkedHashMap instance with the specified capacity.

LinkedHashMap(int initialCapacity, float loadFactor)

Constructs a new LinkedHashMap instance with the specified capacity and load factor.

LinkedHashMap(int initialCapacity, float loadFactor, boolean accessOrder)

Constructs a new LinkedHashMap instance with the specified capacity, load factor and a flag specifying the ordering behavior.

LinkedHashMap(Map<? extends K, ? extends V> map)

Constructs a new LinkedHashMap instance containing the mappings from the specified map.

Public methods

void clear()

Removes all mappings from this hash map, leaving it empty.

boolean containsValue(Object value)

This override is done for LinkedHashMap performance: iteration is cheaper via LinkedHashMap nxt links.

V get(Object key)

Returns the value of the mapping with the specified key.

Protected methods

boolean removeEldestEntry(Entry<K, V> eldest)

Inherited methods

From class java.util.HashMap
From class java.util.AbstractMap
From class java.lang.Object
From interface java.util.Map

Public constructors

LinkedHashMap

Added in API level 1
LinkedHashMap ()

Constructs a new empty LinkedHashMap instance.

LinkedHashMap

Added in API level 1
LinkedHashMap (int initialCapacity)

Constructs a new LinkedHashMap instance with the specified capacity.

Parameters
initialCapacity int: the initial capacity of this map.
Throws
IllegalArgumentException when the capacity is less than zero.

LinkedHashMap

Added in API level 1
LinkedHashMap (int initialCapacity, 
                float loadFactor)

Constructs a new LinkedHashMap instance with the specified capacity and load factor.

Parameters
initialCapacity int: the initial capacity of this map.
loadFactor float: the initial load factor.
Throws
IllegalArgumentException when the capacity is less than zero or the load factor is less or equal to zero.

LinkedHashMap

Added in API level 1
LinkedHashMap (int initialCapacity, 
                float loadFactor, 
                boolean accessOrder)

Constructs a new LinkedHashMap instance with the specified capacity, load factor and a flag specifying the ordering behavior.

Parameters
initialCapacity int: the initial capacity of this hash map.
loadFactor float: the initial load factor.
accessOrder boolean: 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.
Throws
IllegalArgumentException when the capacity is less than zero or the load factor is less or equal to zero.

LinkedHashMap

Added in API level 1
LinkedHashMap (Map<? extends K, ? extends V> map)

Constructs a new LinkedHashMap instance containing the mappings from the specified map. The order of the elements is preserved.

Parameters
map Map: the mappings to add.

Public methods

clear

Added in API level 1
void clear ()

Removes all mappings from this hash map, leaving it empty.

containsValue

Added in API level 1
boolean containsValue (Object value)

This override is done for LinkedHashMap performance: iteration is cheaper via LinkedHashMap nxt links.

Parameters
value Object: the value to search for.
Returns
boolean true if this map contains the specified value, false otherwise.

get

Added in API level 1
V get (Object key)

Returns the value of the mapping with the specified key.

Parameters
key Object: the key.
Returns
V the value of the mapping with the specified key, or null if no mapping for the specified key is found.

Protected methods

removeEldestEntry

Added in API level 1
boolean removeEldestEntry (Entry<K, V> eldest)

Parameters
eldest Entry
Returns
boolean
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