net.rim.device.api.util
Class LongHashtable

java.lang.Object
  net.rim.device.api.util.LongHashtable

All Implemented Interfaces:

Persistable

Direct Known Subclasses:

UserAuthenticatorContextObject

public class LongHashtable
extends Object
implements Persistable

This class implements a hashtable, which maps keys to values.

Any value can be used as a key.

A hashtable has two parameters that affect its efficiency: its capacity and its load factor. The load factor should be between 0.0 and 1.0. When the number of entries in the hashtable exceeds the product of the load factor and the current capacity, the capacity is increased by invoking LongHashtable.rehash(). Larger load factors use memory more efficiently, at the expense of larger expected time per lookup.

If many entries are to be made into a hashtable, creating it with a sufficiently large capacity may allow the entries to be inserted more efficiently than letting it perform automatic rehashing as needed to grow the table.

Constructor Summary

LongHashtable()
Construct a new, empty hashtable with a default capacity and load factor.

LongHashtable(int initialCapacity)
Construct a new, empty hashtable with the specified capacity.

LongHashtable(LongHashtable hashtable)
Construct a new hashtable based on the contents of the given hashtable.

Method Summary
void	clear() Flush this hashtable.
boolean	contains(Object value) Determines if some key maps into the specified value in this hashtable.
boolean	containsKey(long key) Determines if the argument specified is a key in this hashtable.
Enumeration	elements() Retrieves an enumeration of the values in this hashtable.
Object	get(long key) Retrieves value by key.
long	getKey(Object obj) Retrieves key by value.
boolean	isEmpty() Determines if this hashtable maps no keys to values.
LongEnumeration	keys() Retrieves an enumeration of the keys in this hashtable.
int	keysToArray(long[] array) Extract keys into an array.
Object	put(long key, Object value) Maps value to key in this hashtable.
protected void	rehash() Rehashes the contents of this hashtable.
Object	remove(long key) Removes value by key.
void	resetElements(Enumeration e) Resets an enumeration of the values in this hashtable as it would be after a call to LongHashtable.elements().
int	size() Retrieves the number of keys in this hashtable.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LongHashtable

public LongHashtable(int initialCapacity)

Construct a new, empty hashtable with the specified capacity.

Parameters:

initialCapacity - Initial capacity of the hashtable.

Throws:

IllegalArgumentException - If the initial capacity is less than zero

LongHashtable

public LongHashtable()

Construct a new, empty hashtable with a default capacity and load factor.

LongHashtable

public LongHashtable(LongHashtable hashtable)

Construct a new hashtable based on the contents of the given hashtable.

The hashtable itself is copied, however, the references to the objects in the original hashtable are referred to by the new hashtable.

Parameters:

hashtable - Source hashtable.

Method Detail

size

public int size()

Retrieves the number of keys in this hashtable.

Returns:

Number of keys in this hashtable.

isEmpty

public boolean isEmpty()

Determines if this hashtable maps no keys to values.

Returns:

True if this hashtable has no keys mapped to values; otherwise, false.

keys

public LongEnumeration keys()

Retrieves an enumeration of the keys in this hashtable.

Returns:

Enumeration of keys in this hashtable.

See Also:

Enumeration, LongHashtable.elements()

elements

public Enumeration elements()

Retrieves an enumeration of the values in this hashtable.

Use the Enumeration methods on the returned object to fetch the elements sequentially.

Returns:

Enumeration of the values in this hashtable.

See Also:

Enumeration, LongHashtable.keys()

resetElements

public void resetElements(Enumeration e)

Resets an enumeration of the values in this hashtable as it would be after a call to LongHashtable.elements().

Parameters:

e - Enumeration in question.

contains

public boolean contains(Object value)

Determines if some key maps into the specified value in this hashtable.

This operation is more expensive than LongHashtable.containsKey(long).

Parameters:

value - Value to search for.

Returns:

True if some key maps to the provided value in this hashtable; otherwise, false.

Throws:

NullPointerException - If null value provided.

containsKey

public boolean containsKey(long key)

Determines if the argument specified is a key in this hashtable.

Parameters:

key - Key to test.

Returns:

True if the provided argument is a key in this hashtable; otherwise, false.

See Also:

LongHashtable.contains(java.lang.Object)

getKey

public long getKey(Object obj)

Retrieves key by value.

Note: The use of this method is only valid if the element has been verified to be in the table.

Parameters:

obj - Object to locate.

Returns:

The key, or 0 if the element wasn't found.

clear

public void clear()

Flush this hashtable.

Invoke this method to remove all keys and values from this hashtable.

remove

public Object remove(long key)

Removes value by key.

If the key does not exist in this hashtable, then this method does nothing.

Parameters:

key - Key for value to remove.

Returns:

Value that had been associated with key, or null if no value had been associated with key.

get

public Object get(long key)

Retrieves value by key.

Parameters:

key - Key in this hashtable.

Returns:

Value associated with provided key, or null if no value associated with the key.

rehash

protected void rehash()

Rehashes the contents of this hashtable.

Invoke this method to rehash this hashtable into one with a larger capacity. This hashtable invokes this method automatically when the number of keys exceeds its capacity and load factor.

put

public Object put(long key,
                  Object value)

Maps value to key in this hashtable.

The value can be retrieved by invoking LongHashtable.get(long) with a key that is equal to the original key.

Parameters:

key - Key to associate with the value.

value - Value to put into table.

Returns:

Previous value associated with key, or null if key had no previous associated value.

Throws:

NullPointerException - If null key or null value.

keysToArray

public int keysToArray(long[] array)

Extract keys into an array.

Parameters:

array - Array to contain the keys; the array must be large enough to contain all the keys.

Returns:

Number of keys actually extracted.

Throws:

ArrayIndexOutOfBoundsException - If the array isn't big enough.

Since:

BlackBerry API 4.3.0