Package com.sun.jdo.spi.persistence.utility

Class BucketizedHashtable

java.lang.Object

com.sun.jdo.spi.persistence.utility.BucketizedHashtable

All Implemented Interfaces:

Serializable, Cloneable, Map

public class BucketizedHashtable
extends Object
implements Cloneable, Map, Serializable

This class implements bucketize hashtable, which subdivide the key collection stored into several hashtables (buckets) of smaller size. This will reduce the contention of hashtable.

Author:

Shing Wai Chan

See Also:

Serialized Form

Nested Class Summary

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

Map.Entry<K extends Object,V extends Object>

Constructor Summary

Constructors

Constructor	Description
BucketizedHashtable()	Constructs a new, empty BucketizedHashtable with the default bucket size 11, default initial capacity (11 * bucketSize) and default load factor 0.75.
BucketizedHashtable(int bucketSize)	Constructs a new, empty BucketizedHashtable with the specified bucket size, default initial capacity (11 * bucketSize) and default load factor 0.75.
BucketizedHashtable(int bucketSize, int initialCapacity)	Constructs a new, empty BucketizedHashtable with the specified bucket size, initial capacity and default load factor 0.75.
BucketizedHashtable(int bucketSize, int initialCapacity, float loadFactor)	Constructs a new, empty BucketizedHashtable with the specified bucket size, initial capacity and load factor.

Method Summary

Modifier and Type	Method	Description
void	clear()	Clears this BucketizedHashtable so that it contains no key.
Object	clone()	Creates and returns a shallow copy of this object.
boolean	containsKey(Object key)
boolean	containsValue(Object value)
Set	entrySet()	The return set is backed by the map, so changes to the map are reflected in the set, and vice-versa.
boolean	equals(Object o)	Compares the specified object with this map for equality.
Object	get(Object key)
int	hashCode()
boolean	isEmpty()
Set	keySet()	The return set is backed by the map, so changes to the map are reflected in the set, and vice-versa.
Object	put(Object key, Object value)	Maps the specified key to the specified value in this hashtable.
void	putAll(Map t)
Object	remove(Object key)	Remove the key and its corresponding value.
int	size()
String	toString()
Collection	values()	The return collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Constructor Detail

BucketizedHashtable

public BucketizedHashtable(int bucketSize,
                           int initialCapacity,
                           float loadFactor)

Constructs a new, empty BucketizedHashtable with the specified bucket size, initial capacity and load factor.

Parameters:

bucketSize - the number of buckets used for hashing

initialCapacity - the initial capacity of BucketizedHashtable

loadFactor - the load factor of hashtable

BucketizedHashtable

public BucketizedHashtable(int bucketSize,
                           int initialCapacity)

Constructs a new, empty BucketizedHashtable with the specified bucket size, initial capacity and default load factor 0.75.

Parameters:

bucketSize - the number of buckets used for hashing

initialCapacity - the initial capacity of hashtable

BucketizedHashtable

public BucketizedHashtable(int bucketSize)

Constructs a new, empty BucketizedHashtable with the specified bucket size, default initial capacity (11 * bucketSize) and default load factor 0.75.

Parameters:

bucketSize - the number of buckets used for hashing

BucketizedHashtable

public BucketizedHashtable()

Constructs a new, empty BucketizedHashtable with the default bucket size 11, default initial capacity (11 * bucketSize) and default load factor 0.75.

Method Detail

get

public Object get(Object key)

Specified by:

get in interface Map

Parameters:

key - a key in the hashtable

Returns:

the value to which the specified key is mapped.

remove

public Object remove(Object key)

Remove the key and its corresponding value.

Specified by:

remove in interface Map

Parameters:

key - the key that needs to be removed

Returns:

the value to which the key had been mapped, or null if the key did not have a mapping.

put

public Object put(Object key,
                  Object value)

Maps the specified key to the specified value in this hashtable. Neither the key nor the value can be null.

Specified by:

put in interface Map

Parameters:

key - the hashtable key

value - the value

Returns:

the previous value of the specified key in hashtables, or null if it did not have one.

putAll

public void putAll(Map t)

Specified by:

putAll in interface Map

Parameters:

t - BucketizedHashtable or a Map with a supported operation entrySet

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map

Parameters:

key - possible key

Returns:

true if and only if the specified object is a key in one of of the hashtables

containsValue

public boolean containsValue(Object value)

Specified by:

containsValue in interface Map

Parameters:

value - possible value

Returns:

true if and only if the specified object is a value in one of of the hashtables

size

public int size()

Specified by:

size in interface Map

Returns:

the total number of key-value mappings of all buckets

hashCode

public int hashCode()

Specified by:

hashCode in interface Map

Overrides:

hashCode in class Object

Returns:

the hash code value for this map

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map

Returns:

true if this map contains no key-value mappings

clear

public void clear()

Clears this BucketizedHashtable so that it contains no key.

Specified by:

clear in interface Map

entrySet

public Set entrySet()

The return set is backed by the map, so changes to the map are reflected in the set, and vice-versa.

Specified by:

entrySet in interface Map

Returns:

a set of Map.Entry when bucketSet equal 1

Throws:

UnsupportedOperationException - when bucketSize is greater one

keySet

public Set keySet()

The return set is backed by the map, so changes to the map are reflected in the set, and vice-versa.

Specified by:

keySet in interface Map

Returns:

a set of keys when bucketSet equal 1

Throws:

UnsupportedOperationException - when bucketSize is greater one

values

public Collection values()

The return collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa.

Specified by:

values in interface Map

Returns:

a collection of values when bucketSet equal 1

Throws:

UnsupportedOperationException - when bucketSize is greater one

equals

public boolean equals(Object o)

Compares the specified object with this map for equality.

Specified by:

equals in interface Map

Overrides:

equals in class Object

Returns:

true if the specified object is a BucketizedHashtable with hashtables represent the same set of mappings.

clone

public Object clone()

Creates and returns a shallow copy of this object. The keys and values are not cloned.

Overrides:

clone in class Object

Returns:

a clone of BucketizedHashtable

toString

public String toString()

Overrides:

toString in class Object

Returns:

a string representation of this BucketizedHashtable