edu.umass.cs.mallet.base.types

Class Alphabet

java.lang.Object

edu.umass.cs.mallet.base.types.Alphabet

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

LabelAlphabet

public class Alphabet
extends Object
implements Serializable

A mapping between integers and objects where the mapping in each direction is efficient. Integers are assigned consecutively, starting at zero, as objects are added to the Alphabet. Objects can not be deleted from the Alphabet and thus the integers are never reused.

The most common use of an alphabet is as a dictionary of feature names associated with a FeatureVector in an Instance. In a simple document classification usage, each unique word in a document would be a unique entry in the Alphabet with a unique integer associated with it. FeatureVectors rely on the integer part of the mapping to efficiently represent the subset of the Alphabet present in the FeatureVector.

See Also:

FeatureVector, Instance, Pipe, Serialized Form

Constructor Summary

Constructors

Constructor and Description
Alphabet()
Alphabet(Class entryClass)
Alphabet(int capacity)
Alphabet(int capacity, Class entryClass)

Method Summary

Modifier and Type	Method and Description
Object	clone()
boolean	contains(Object entry)
void	dump()
void	dump(PrintStream out)
void	dump(PrintWriter out)
Class	entryClass()
VMID	getInstanceId()
boolean	growthStopped()
Iterator	iterator()
int	lookupIndex(Object entry)
int	lookupIndex(Object entry, boolean addIfNotPresent) Return -1 if entry isn't present.
int[]	lookupIndices(Object[] objects, boolean addIfNotPresent)
Object	lookupObject(int index)
Object[]	lookupObjects(int[] indices)
Object[]	lookupObjects(int[] indices, Object[] buf) Returns an array of the objects corresponding to
Object	readResolve() This gets called after readObject; it lets the object decide whether to return itself or return a previously read in version.
void	setInstanceId(VMID id)
int	size()
void	startGrowth()
void	stopGrowth()
Object[]	toArray()
Object[]	toArray(Object[] in) Returns an array containing all the entries in the Alphabet.
String	toString() Return String representation of all Alphabet entries, each separated by a newline.

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Alphabet

public Alphabet(int capacity,
                Class entryClass)

Alphabet

public Alphabet(Class entryClass)

Alphabet

public Alphabet(int capacity)

Alphabet

public Alphabet()

Method Detail

clone

public Object clone()

Overrides:

clone in class Object

lookupIndex

public int lookupIndex(Object entry,
                       boolean addIfNotPresent)

Return -1 if entry isn't present.

lookupIndex

public int lookupIndex(Object entry)

lookupObject

public Object lookupObject(int index)

toArray

public Object[] toArray()

toArray

public Object[] toArray(Object[] in)

Returns an array containing all the entries in the Alphabet. The runtime type of the returned array is the runtime type of in. If in is large enough to hold everything in the alphabet, then it it used. The returned array is such that for all entries obj, ret[lookupIndex(obj)] = obj .

iterator

public Iterator iterator()

lookupObjects

public Object[] lookupObjects(int[] indices)

lookupObjects

public Object[] lookupObjects(int[] indices,
                              Object[] buf)

Returns an array of the objects corresponding to

Parameters:

indices - An array of indices to look up

buf - An array to store the returned objects in.

Returns:

An array of values from this Alphabet. The runtime type of the array is the same as buf

lookupIndices

public int[] lookupIndices(Object[] objects,
                           boolean addIfNotPresent)

contains

public boolean contains(Object entry)

size

public int size()

stopGrowth

public void stopGrowth()

startGrowth

public void startGrowth()

growthStopped

public boolean growthStopped()

entryClass

public Class entryClass()

toString

public String toString()

Return String representation of all Alphabet entries, each separated by a newline.

Overrides:

toString in class Object

dump

public void dump()

dump

public void dump(PrintStream out)

dump

public void dump(PrintWriter out)

getInstanceId

public VMID getInstanceId()

setInstanceId

public void setInstanceId(VMID id)

readResolve

public Object readResolve()
                   throws ObjectStreamException

This gets called after readObject; it lets the object decide whether to return itself or return a previously read in version. We use a hashMap of instanceIds to determine if we have already read in this object.

Returns:

Throws:

ObjectStreamException