Opus5
Class AbstractHashTable

java.lang.Object
  |
  +--Opus5.AbstractObject
        |
        +--Opus5.AbstractContainer
              |
              +--Opus5.AbstractSearchableContainer
                    |
                    +--Opus5.AbstractHashTable

All Implemented Interfaces:

Comparable, Container, HashTable, SearchableContainer

Direct Known Subclasses:

ChainedHashTable, ChainedScatterTable, OpenScatterTable

public abstract class AbstractHashTable

extends AbstractSearchableContainer

implements HashTable

The AbstractHashTable class is the base class from which all concrete hash and scatter table classes are derived. This abstract class provides default implementations for various methods declared in the HashTable interface.

Version:

$Id: AbstractHashTable.java,v 3.2 1998/07/28 13:00:41 brpreiss Exp $

Author:

Bruno R. Preiss, P.Eng.

See Also:

HashTable

Fields inherited from class Opus5.AbstractContainer

count

Fields inherited from interface Opus5.HashTable

copyright

Constructor Summary

AbstractHashTable()

Method Summary

protected int	f(java.lang.Object object) Returns the hashcode for the specified object.
protected int	g(int x) Hashes an integer using the division method of hashing.
abstract int	getLength() Returns the length of this hash table.
double	getLoadFactor() Computes the current load factor for this hash table.
protected int	h(java.lang.Object object) Hashes the specified object using the composition of the methods f and g.

Methods inherited from class Opus5.AbstractContainer

accept, getCount, hashCode, isEmpty, isFull, toString

Methods inherited from class Opus5.AbstractObject

compare, compareTo, equals, isEQ, isGE, isGT, isLE, isLT, isNE

Methods inherited from class java.lang.Object

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

Methods inherited from interface Opus5.SearchableContainer

find, insert, isMember, withdraw

Methods inherited from interface Opus5.Container

accept, getCount, getEnumeration, isEmpty, isFull, purge

Methods inherited from interface Opus5.Comparable

compare, isEQ, isGE, isGT, isLE, isLT, isNE

Constructor Detail

AbstractHashTable

public AbstractHashTable()

Method Detail

getLength

public abstract int getLength()

Returns the length of this hash table.

Returns:

The length of this hash table.

f

protected final int f(java.lang.Object object)

Returns the hashcode for the specified object. Implemented as follows:

 return object.hashCode ();
 

Parameters:

object - The object the hashcode of which is returned.

Returns:

The hashcode for the specified object.

g

protected final int g(int x)

Hashes an integer using the division method of hashing. Implemented as follows:

 return Math.abs (x) % getLength ();
 

Parameters:

x - The integer to be hashed.

Returns:

A positive integer in the interval [0,Length()-1].

h

protected final int h(java.lang.Object object)

Hashes the specified object using the composition of the methods f and g. Implemented as follows:

 return g(f(object));
 

Parameters:

object - The object to be hashed.

Returns:

A positive integer in the interval [0,Length()-1].

getLoadFactor

public final double getLoadFactor()

Computes the current load factor for this hash table. Implemented as follows:

 return (double) getCount () / getLength ();
 

Specified by:

getLoadFactor in interface HashTable

Returns:

The current load factor for this hash table.