es.upm.etsisi.cf4j.data

Class Item

java.lang.Object

es.upm.etsisi.cf4j.data.Item

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

TestItem

public class Item
extends Object
implements Serializable

Defines a composition of an Item. An item is composed by:

• Item unique identifier.
• Item index in the DataModel which stores it.
• Array of ratings made by users.

It is not recommended that developers generate new instances of this class since this is a memory-structural class.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected double	average Average (training) rating
protected DataBank	dataBank DataBank to store heterogeneous information
protected String	id Item unique identifier
protected int	itemIndex Item index in the DataModel
protected double	max Maximum (training) rating value
protected double	min Minimum (training) rating value
protected SortedRatingList	usersRatings Users that have rated the item

Constructor Summary

Constructors

Constructor and Description
Item(String id, int index) Creates a new instance of an item.

Method Summary

Modifier and Type	Method and Description
void	addRating(int userIndex, double rating) Adds a new rating of an user to the item.
int	findUser(int userIndex) Finds position of a rating that an user has made to the item given the index of the User in the DataModel.
DataBank	getDataBank() Gets the DataBank instance that stores heterogeneous information related to the Item.
String	getId() Returns the item unique identifier
int	getItemIndex() Return the item index inside the DataModel
double	getMaxRating() Gets the maximum rating received by the item.
double	getMinRating() Gets the minimum rating received by the item.
int	getNumberOfRatings() Gets the number of ratings that the item have received
double	getRatingAt(int pos) Returns the rating of the user to the item at the pos position
double	getRatingAverage() Gets the average value of ratings
int	getUserAt(int pos) Returns the index of the User that have rated the Item at the given position

Methods inherited from class java.lang.Object

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

Field Detail

id

protected String id

Item unique identifier

itemIndex

protected int itemIndex

Item index in the DataModel

min

protected double min

Minimum (training) rating value

max

protected double max

Maximum (training) rating value

average

protected double average

Average (training) rating

dataBank

protected DataBank dataBank

DataBank to store heterogeneous information

usersRatings

protected SortedRatingList usersRatings

Users that have rated the item

Constructor Detail

Item

public Item(String id,
            int index)

Creates a new instance of an item. This constructor should not be used by developers.

Parameters:

id - Item unique identifier

index - Index of the item in the Items' array of the DataModel

Method Detail

getDataBank

public DataBank getDataBank()

Gets the DataBank instance that stores heterogeneous information related to the Item.

Returns:

DataBank instance

getId

public String getId()

Returns the item unique identifier

Returns:

Item identifier

getItemIndex

public int getItemIndex()

Return the item index inside the DataModel

Returns:

Item index inside the DataModel

getUserAt

public int getUserAt(int pos)

Returns the index of the User that have rated the Item at the given position

Parameters:

pos - Position

Returns:

Index of the user in the Users' array of the DataModel

getRatingAt

public double getRatingAt(int pos)

Returns the rating of the user to the item at the pos position

Parameters:

pos - Position

Returns:

Rating at indicated position

findUser

public int findUser(int userIndex)

Finds position of a rating that an user has made to the item given the index of the User in the DataModel.

Parameters:

userIndex - User index

Returns:

User position if the item has been rated by the user or -1 if do not

getNumberOfRatings

public int getNumberOfRatings()

Gets the number of ratings that the item have received

Returns:

Number of ratings

addRating

public void addRating(int userIndex,
                      double rating)

Adds a new rating of an user to the item. You cannot overwrite an existing rating, otherwise this method will throws an IllegalArgumentException. It is not recommended to use this method, use DataModel.addRating(...) instead.

Parameters:

userIndex - User index which identifies the specific user in the DataModel

rating - Rating value

getMinRating

public double getMinRating()

Gets the minimum rating received by the item.

Returns:

Minimum rating

getMaxRating

public double getMaxRating()

Gets the maximum rating received by the item.

Returns:

Maximum rating

getRatingAverage

public double getRatingAverage()

Gets the average value of ratings

Returns:

Rating average