org.gudy.azureus2.core3.util
Class LightHashMap<S,T>

java.lang.Object
  java.util.AbstractMap<S,T>
      org.gudy.azureus2.core3.util.LightHashMap<S,T>

All Implemented Interfaces:

java.lang.Cloneable, java.util.Map<S,T>

Direct Known Subclasses:

JSONObject, LightHashMapEx

public class LightHashMap<S,T>
extends java.util.AbstractMap<S,T>
implements java.lang.Cloneable

A lighter (on memory) hash map
Advantages over HashMap:

• Lower memory footprint
• Everything is stored in a single array, this might improve cache performance (not verified)
• Read-only operations on Key and Value iterators should be concurrency-safe (Entry iterators are not) but they might return null values unexpectedly under concurrent modification (not verified)

Disadvantages:

• removal is implemented with thombstone-keys, this can significantly increase the lookup time if many values are removed. Use compactify() for scrubbing
• entry set iterators and thus transfers to other maps are slower than compareable implementations
• the map does not store hashcodes and relies on either the key-objects themselves caching them (such as strings) or a fast computation of hashcodes
• concurrent modification detection is not as fail-fast as HashMap as no modification counter is used and only structural differences are noted

Author:

Aaron Grunthal

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

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

java.util.Map.Entry<K,V>

Constructor Summary

LightHashMap()

LightHashMap(int initialCapacity)

LightHashMap(int initialCapacity, float loadFactor)

LightHashMap(java.util.Map m)

Method Summary

int	capacity()
void	clear()
java.lang.Object	clone()
void	compactify(float compactingLoadFactor) will shrink the internal storage size to the least possible amount, should be used after removing many entries for example
boolean	containsKey(java.lang.Object key)
boolean	containsValue(java.lang.Object value)
java.util.Set	entrySet()
T	get(java.lang.Object key)
java.util.Set<S>	keySet()
static void	main(java.lang.String[] args)
T	put(java.lang.Object key, java.lang.Object value)
void	putAll(java.util.Map m)
T	remove(java.lang.Object key)
java.util.Collection<T>	values()

Methods inherited from class java.util.AbstractMap

equals, hashCode, isEmpty, size, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

LightHashMap

public LightHashMap()

LightHashMap

public LightHashMap(int initialCapacity)

LightHashMap

public LightHashMap(java.util.Map m)

LightHashMap

public LightHashMap(int initialCapacity,
                    float loadFactor)

Method Detail

clone

public java.lang.Object clone()

Overrides:

clone in class java.util.AbstractMap<S,T>

entrySet

public java.util.Set entrySet()

Specified by:

entrySet in interface java.util.Map<S,T>

Specified by:

entrySet in class java.util.AbstractMap<S,T>

put

public T put(java.lang.Object key,
             java.lang.Object value)

Specified by:

put in interface java.util.Map<S,T>

Overrides:

put in class java.util.AbstractMap<S,T>

putAll

public void putAll(java.util.Map m)

Specified by:

putAll in interface java.util.Map<S,T>

Overrides:

putAll in class java.util.AbstractMap<S,T>

keySet

public java.util.Set<S> keySet()

Specified by:

keySet in interface java.util.Map<S,T>

Overrides:

keySet in class java.util.AbstractMap<S,T>

values

public java.util.Collection<T> values()

Specified by:

values in interface java.util.Map<S,T>

Overrides:

values in class java.util.AbstractMap<S,T>

capacity

public int capacity()

get

public T get(java.lang.Object key)

Specified by:

get in interface java.util.Map<S,T>

Overrides:

get in class java.util.AbstractMap<S,T>

remove

public T remove(java.lang.Object key)

Specified by:

remove in interface java.util.Map<S,T>

Overrides:

remove in class java.util.AbstractMap<S,T>

clear

public void clear()

Specified by:

clear in interface java.util.Map<S,T>

Overrides:

clear in class java.util.AbstractMap<S,T>

containsKey

public boolean containsKey(java.lang.Object key)

Specified by:

containsKey in interface java.util.Map<S,T>

Overrides:

containsKey in class java.util.AbstractMap<S,T>

containsValue

public boolean containsValue(java.lang.Object value)

Specified by:

containsValue in interface java.util.Map<S,T>

Overrides:

containsValue in class java.util.AbstractMap<S,T>

compactify

public void compactify(float compactingLoadFactor)

will shrink the internal storage size to the least possible amount, should be used after removing many entries for example

Parameters:

compactingLoadFactor - load factor for the compacting operation. Use 0f to compact with the load factor specified during instantiation. Use negative values of the desired load factors to compact only when it would reduce the storage size.

main

public static void main(java.lang.String[] args)