org.dspace.content

Class ItemComparator

java.lang.Object

org.dspace.content.ItemComparator

All Implemented Interfaces:

Serializable, Comparator

public class ItemComparator
extends Object
implements Comparator, Serializable

Compare two Items by their DCValues. The DCValues to be compared are specified by the element, qualifier and language parameters to the constructor. If the Item has more than one matching Metadatum, then the max parameter to the constructor specifies whether the maximum or minimum lexicographic value will be used.

Version:

$Revision$

Author:

Peter Breton

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected String	element Dublin Core element
protected ItemService	itemService
protected String	language Language
protected boolean	max Whether maximum or minimum value will be used
protected String	qualifier Dublin Core qualifier

Constructor Summary

Constructors

Constructor and Description
ItemComparator(String element, String qualifier, String language, boolean max) Constructor.

Method Summary

Modifier and Type	Method and Description
int	compare(Object first, Object second) Compare two Items by checking their DCValues for element, qualifier, and language.
boolean	equals(Object obj) Return true if the object is equal to this one, false otherwise.
protected boolean	equalsWithNull(String first, String second)
protected String	getValue(Item item) Choose the canonical value from an item for comparison.
int	hashCode()
protected String	normalizeTitle(MetadataValue value) Normalize the title of a Metadatum.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Field Detail

element

protected String element

Dublin Core element

qualifier

protected String qualifier

Dublin Core qualifier

language

protected String language

Language

max

protected boolean max

Whether maximum or minimum value will be used

itemService

protected transient ItemService itemService

Constructor Detail

ItemComparator

public ItemComparator(String element,
                      String qualifier,
                      String language,
                      boolean max)

Constructor.

Parameters:

element - The Dublin Core element

qualifier - The Dublin Core qualifier

language - The language for the DCValues

max - If true, and there is more than one Metadatum for element, qualifier and language, then use the maximum value lexicographically; otherwise use the minimum value.

Method Detail

compare

public int compare(Object first,
                   Object second)

Compare two Items by checking their DCValues for element, qualifier, and language.

Return greater than or equal to 1 if the first is lexicographically greater than the second; less than or equal to -1 if the second is lexicographically greater than the first, and 0 otherwise.

Specified by:

compare in interface Comparator

Parameters:

first - The first object to compare. Must be an object of type org.dspace.content.Item.

second - The second object to compare. Must be an object of type org.dspace.content.Item.

Returns:

greater than or equal 1 if the first is lexicographically greater than the second; less than or equal -1 if the second is lexicographically greater than the first, and 0 otherwise.

equals

public boolean equals(Object obj)

Return true if the object is equal to this one, false otherwise. Another object is equal to this one if it is also an ItemComparator, and has the same values for element, qualifier, language, and max.

Specified by:

equals in interface Comparator

Overrides:

equals in class Object

Parameters:

obj - The object to compare to.

Returns:

True if the other object is equal to this one, false otherwise.

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equalsWithNull

protected boolean equalsWithNull(String first,
                                 String second)

Parameters:

first -

second -

Returns:

true if the first string is equal to the second. Either or both may be null.

getValue

protected String getValue(Item item)

Choose the canonical value from an item for comparison. If there are no values, null is returned. If there is exactly one value, then it is returned. Otherwise, either the maximum or minimum lexicographical value is returned; the parameter to the constructor says which.

Parameters:

item - The item to check

Returns:

The chosen value, or null

normalizeTitle

protected String normalizeTitle(MetadataValue value)

Normalize the title of a Metadatum.

Parameters:

value -

Returns:

normalized title