com.neeve.util
Class UtlLinkedHashMap<K,V>

java.lang.Object
  com.neeve.util.UtlLinkedHashMap<K,V>

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>

public class UtlLinkedHashMap<K,V>
extends Object
implements Map<K,V>, Cloneable, Serializable

This class represents a Map collection with real-time behavior. Unless the map's size exceeds its current capacity, no dynamic memory allocation is ever performed and response time is extremely fast and consistent.

UtlLinkedHashMap has a predictable iteration order, which is the order in which keys were inserted into the map (similar to java.util.LinkedHashMap collection class). A bi-directional list iterator over the map entries is also provided, this iterator can be moved to the first or to the last entry for unlimited reuse.

Applications may change the resizing policy of UtlLinkedHashMap by overriding the sizeChanged() method. For example, to reduce memory footprint, the map's capacity could be maitained at ±50% of the current map's size.

This implementation is not synchronized. Multiple threads accessing or modifying the collection must be synchronized externally.

Note: To avoid dynamic memory allocations, UtlLinkedHashMap maintains an internal pool of Map.Entry objects. The size of the pool is determined by the map's capacity. When an entry is removed from the map, it is automatically restored to the pool.

Modified from: http://www.java2s.com/Code/Java/Collections-Data-Structure/AMapcollectionwithrealtimebehavior.htm

This class IS NOT intended to be used by end users.

See Also:

Serialized Form

Threading:

This class is not safe for concurrent access by multiple threads.

Nested Class Summary

class

UtlLinkedHashMap.FastIterator This inner class represents a reusable list iterator over UtlLinkedHashMap entries.

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Constructor Summary

UtlLinkedHashMap()
Creates a UtlLinkedHashMap with a capacity of 16 entries.

UtlLinkedHashMap(int capacity)
Creates a UtlLinkedHashMap with the specified capacity.

UtlLinkedHashMap(Map<K,V> map)
Creates a UtlLinkedHashMap, copy of the specified Map.

Method Summary

int	capacity() Returns the capacity of this UtlLinkedHashMap.
void	clear() Removes all mappings from this UtlLinkedHashMap.
Object	clone() Returns a shallow copy of this UtlLinkedHashMap.
boolean	containsKey(Object key) Indicates if this UtlLinkedHashMap contains a mapping for the specified key.
boolean	containsValue(Object value) Indicates if this UtlLinkedHashMap maps one or more keys to the specified value.
Set<Map.Entry<K,V>>	entrySet() Returns a collection view of the mappings contained in this UtlLinkedHashMap.
boolean	equals(Object obj) Compares the specified object with this UtlLinkedHashMap for equality.
UtlLinkedHashMap.FastIterator	fastIterator() Returns a reusable UtlLinkedHashMap.FastIterator over this UtlLinkedHashMap entries (unique instance per map).
V	get(Object key) Returns the value to which this UtlLinkedHashMap maps the specified key.
Map.Entry<K,V>	getEntry(K key) Returns the entry with the specified key.
int	hashCode() Returns the hash code value for this UtlLinkedHashMap.
boolean	isEmpty() Indicates if this UtlLinkedHashMap contains no key-value mappings.
Set<K>	keySet() Returns a set view of the keys contained in this UtlLinkedHashMap.
V	put(K key, V value) Associates the specified value with the specified key in this UtlLinkedHashMap.
void	putAll(Map<? extends K,? extends V> map) Copies all of the mappings from the specified map to this UtlLinkedHashMap.
V	remove(Object key) Removes the mapping for this key from this UtlLinkedHashMap if present.
void	setCapacity(int newCapacity) Changes the current capacity of this UtlLinkedHashMap.
int	size() Returns the number of key-value mappings in this UtlLinkedHashMap.
String	toString() Returns a String representation of this UtlLinkedHashMap.
Collection<V>	values() Returns a collection view of the values contained in this UtlLinkedHashMap.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

UtlLinkedHashMap

public UtlLinkedHashMap()

Creates a UtlLinkedHashMap with a capacity of 16 entries.

UtlLinkedHashMap

public UtlLinkedHashMap(Map<K,V> map)

Creates a UtlLinkedHashMap, copy of the specified Map. If the specified map is not an instance of UtlLinkedHashMap, the newly created map has a capacity set to the specified map's size. The copy has the same order as the original, regardless of the original map's implementation:

     TreeMap dictionary = ...;
     UtlLinkedHashMap dictionaryLookup = new UtlLinkedHashMap(dictionary);
 

Parameters:

map - the map whose mappings are to be placed in this map.

UtlLinkedHashMap

public UtlLinkedHashMap(int capacity)

Creates a UtlLinkedHashMap with the specified capacity. Unless the capacity is exceeded, operations on this map do not allocate entries. For optimum performance, the capacity should be of the same order of magnitude or larger than the expected map's size.

Parameters:

capacity - the number of buckets in the hash table; it also defines the number of pre-allocated entries.

Method Detail

size

public int size()

Returns the number of key-value mappings in this UtlLinkedHashMap.

Specified by:

size in interface Map<K,V>

Returns:

this map's size.

capacity

public int capacity()

Returns the capacity of this UtlLinkedHashMap. The capacity defines the number of buckets in the hash table, as well as the maximum number of entries the map may contain without allocating memory.

Returns:

this map's capacity.

isEmpty

public boolean isEmpty()

Indicates if this UtlLinkedHashMap contains no key-value mappings.

Specified by:

isEmpty in interface Map<K,V>

Returns:

true if this map contains no key-value mappings; false otherwise.

containsKey

public boolean containsKey(Object key)

Indicates if this UtlLinkedHashMap contains a mapping for the specified key.

Specified by:

containsKey in interface Map<K,V>

Parameters:

key - the key whose presence in this map is to be tested.

Returns:

true if this map contains a mapping for the specified key; false otherwise.

Throws:

NullPointerException - if the key is null.

containsValue

public boolean containsValue(Object value)

Indicates if this UtlLinkedHashMap maps one or more keys to the specified value.

Specified by:

containsValue in interface Map<K,V>

Parameters:

value - the value whose presence in this map is to be tested.

Returns:

true if this map maps one or more keys to the specified value.

Throws:

NullPointerException - if the key is null.

get

public V get(Object key)

Returns the value to which this UtlLinkedHashMap maps the specified key.

Specified by:

get in interface Map<K,V>

Parameters:

key - the key whose associated value is to be returned.

Returns:

the value to which this map maps the specified key, or null if there is no mapping for the key.

Throws:

NullPointerException - if key is null.

getEntry

public Map.Entry<K,V> getEntry(K key)

Returns the entry with the specified key.

Parameters:

key - the key whose associated entry is to be returned.

Returns:

the entry for the specified key or null if none.

put

public V put(K key,
             V value)

Associates the specified value with the specified key in this UtlLinkedHashMap. If the UtlLinkedHashMap previously contained a mapping for this key, the old value is replaced.

Specified by:

put in interface Map<K,V>

Parameters:

key - the key with which the specified value is to be associated.

value - the value to be associated with the specified key.

Returns:

the 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.

Throws:

NullPointerException - if the key is null.

fastIterator

public UtlLinkedHashMap.FastIterator fastIterator()

Returns a reusable UtlLinkedHashMap.FastIterator over this UtlLinkedHashMap entries (unique instance per map). For example:

 
     // Iteration without memory allocation!
     for (FastIterator i=map.fastIterator().toFirst(); i.hasNext();) {
         Entry entry = i.nextEntry();
         ...
     }

Returns:

an iterator which can be reset for reuse over and over.

See Also:

UtlLinkedHashMap.FastIterator

putAll

public void putAll(Map<? extends K,? extends V> map)

Copies all of the mappings from the specified map to this UtlLinkedHashMap.

Specified by:

putAll in interface Map<K,V>

Parameters:

map - the mappings to be stored in this map.

Throws:

NullPointerException - the specified map is null, or the specified map contains null keys.

remove

public V remove(Object key)

Removes the mapping for this key from this UtlLinkedHashMap if present.

Specified by:

remove in interface Map<K,V>

Parameters:

key - the 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.

Throws:

NullPointerException - if the key is null.

clear

public void clear()

Removes all mappings from this UtlLinkedHashMap.

Specified by:

clear in interface Map<K,V>

setCapacity

public void setCapacity(int newCapacity)

Changes the current capacity of this UtlLinkedHashMap. If the capacity is increased, new entries are allocated and added to the pool. If the capacity is decreased, entries from the pool are deallocated (and are garbage collected eventually). The capacity also determined the number of buckets for the hash table.

Parameters:

newCapacity - the new capacity of this map.

clone

public Object clone()

Returns a shallow copy of this UtlLinkedHashMap. The keys and the values themselves are not cloned.

Overrides:

clone in class Object

Returns:

a shallow copy of this map.

equals

public boolean equals(Object obj)

Compares the specified object with this UtlLinkedHashMap for equality. Returns true if the given object is also a map and the two maps represent the same mappings (regardless of collection iteration order).

Specified by:

equals in interface Map<K,V>

Overrides:

equals in class Object

Parameters:

obj - the object to be compared for equality with this map.

Returns:

true if the specified object is equal to this map; false otherwise.

hashCode

public int hashCode()

Returns the hash code value for this UtlLinkedHashMap.

Specified by:

hashCode in interface Map<K,V>

Overrides:

hashCode in class Object

Returns:

the hash code value for this map.

toString

public String toString()

Returns a String representation of this UtlLinkedHashMap.

Overrides:

toString in class Object

Returns:

this.entrySet().toString();

values

public Collection<V> values()

Returns a collection view of the values contained in this UtlLinkedHashMap. 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<K,V>

Returns:

a collection view of the values contained in this map.

entrySet

public Set<Map.Entry<K,V>> entrySet()

Returns a collection view of the mappings contained in this UtlLinkedHashMap. 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 this 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<K,V>

Returns:

a collection view of the mappings contained in this map.

keySet

public Set<K> keySet()

Returns a set view of the keys contained in this UtlLinkedHashMap. 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, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

keySet in interface Map<K,V>

Returns:

a set view of the keys contained in this map.