Class LinkedHashMap<K,V>

public LinkedHashMap()

Construct a new insertion-ordered LinkedHashMap with the default capacity (11) and the default load factor (0.75).

public LinkedHashMap(extends K,
 V> m)

Construct a new insertion-ordered LinkedHashMap from the given Map, with initial capacity the greater of the size of m or the default of 11.

Every element in Map m will be put into this new HashMap, in the order of m's iterator.

Parameters:

m - a Map whose key / value pairs will be put into the new HashMap. NOTE: key / value pairs are not cloned in this constructor.

Throws:

NullPointerException - if m is null

public LinkedHashMap(int initialCapacity)

Construct a new insertion-ordered LinkedHashMap with a specific inital capacity and default load factor of 0.75.

Parameters:

initialCapacity - the initial capacity of this HashMap (>= 0)

Throws:

IllegalArgumentException - if (initialCapacity < 0)

public LinkedHashMap(int initialCapacity,
 float loadFactor)

Construct a new insertion-orderd LinkedHashMap with a specific inital capacity and load factor.

Parameters:

initialCapacity - the initial capacity (>= 0)

loadFactor - the load factor (> 0, not NaN)

Throws:

IllegalArgumentException - if (initialCapacity < 0) || ! (loadFactor > 0.0)

public LinkedHashMap(int initialCapacity,
 float loadFactor,
 boolean accessOrder)

Construct a new LinkedHashMap with a specific inital capacity, load factor, and ordering mode.

Parameters:

initialCapacity - the initial capacity (>=0)

loadFactor - the load factor (>0, not NaN)

accessOrder - true for access-order, false for insertion-order

Throws:

IllegalArgumentException - if (initialCapacity < 0) || ! (loadFactor > 0.0)

public void clear()

Clears the Map so it has no keys. This is O(1).

Specified by:

clear in interface Map<K,V>

Overrides:

clear in interface HashMap<K,V>

public boolean containsValue(Object value)

Returns true if this HashMap contains a value o, such that o.equals(value).

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in interface HashMap<K,V>

Parameters:

value - the value to search for in this HashMap

Returns:

true if at least one key maps to the value

public V get(Object key)

Return the value in this Map associated with the supplied key, or null if the key maps to nothing. If this is an access-ordered Map and the key is found, this performs structural modification, moving the key to the newest end of the list. NOTE: Since the value could also be null, you must use containsKey to see if this key actually maps to something.

Specified by:

get in interface Map<K,V>

Overrides:

get in interface HashMap<K,V>

Parameters:

key - the key for which to fetch an associated value

Returns:

what the key maps to, if present

See Also:

put(Object, Object), containsKey(Object)

protected boolean removeEldestEntry(java.util.Map.Entry eldest)

Returns true if this map should remove the eldest entry. This method is invoked by all calls to put and putAll which place a new entry in the map, providing the implementer an opportunity to remove the eldest entry any time a new one is added. This can be used to save memory usage of the hashtable, as well as emulating a cache, by deleting stale entries.

For example, to keep the Map limited to 100 entries, override as follows:

 private static final int MAX_ENTRIES = 100;
 protected boolean removeEldestEntry(Map.Entry eldest)
 {
 return size() > MAX_ENTRIES;
 }
 

Typically, this method does not modify the map, but just uses the return value as an indication to put whether to proceed. However, if you override it to modify the map, you must return false (indicating that put should leave the modified map alone), or you face unspecified behavior. Remember that in access-order mode, even calling get is a structural modification, but using the collections views (such as keySet) is not.

This method is called after the eldest entry has been inserted, so if put was called on a previously empty map, the eldest entry is the one you just put in! The default implementation just returns false, so that this map always behaves like a normal one with unbounded growth.

Parameters:

eldest - the eldest element which would be removed if this returns true. For an access-order map, this is the least recently accessed; for an insertion-order map, this is the earliest element inserted.

Returns:

true if eldest should be removed