org.apache.lucene.search
Class SortComparator

java.lang.Object
  org.apache.lucene.search.SortComparator

All Implemented Interfaces:

Serializable, SortComparatorSource

public abstract class SortComparator
extends Object
implements SortComparatorSource

Abstract base class for sorting hits returned by a Query.

This class should only be used if the other SortField types (SCORE, DOC, STRING, INT, FLOAT) do not provide an adequate sorting. It maintains an internal cache of values which could be quite large. The cache is an array of Comparable, one for each document in the index. There is a distinct Comparable for each unique term in the field - if some documents have the same term in the field, the cache array will have entries which reference the same Comparable.

Created: Apr 21, 2004 5:08:38 PM

Since:

1.4

Version:

$Id: SortComparator.java 564236 2007-08-09 15:21:19Z gsingers $

See Also:

Serialized Form

Constructor Summary

SortComparator()

Method Summary

protected abstract Comparable	getComparable(String termtext) Returns an object which, when sorted according to natural order, will order the Term values in the correct order.
ScoreDocComparator	newComparator(IndexReader reader, String fieldname) Creates a comparator for the field in the given index.

Methods inherited from class java.lang.Object

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

Constructor Detail

SortComparator

public SortComparator()

Method Detail

newComparator

public ScoreDocComparator newComparator(IndexReader reader,
                                        String fieldname)
                                 throws IOException

Description copied from interface: SortComparatorSource

Creates a comparator for the field in the given index.

Specified by:

newComparator in interface SortComparatorSource

Parameters:

reader - Index to create comparator for.

fieldname - Name of the field to create comparator for.

Returns:

Comparator of ScoreDoc objects.

Throws:

IOException - If an error occurs reading the index.

getComparable

protected abstract Comparable getComparable(String termtext)

Returns an object which, when sorted according to natural order, will order the Term values in the correct order.

For example, if the Terms contained integer values, this method would return new Integer(termtext). Note that this might not always be the most efficient implementation - for this particular example, a better implementation might be to make a ScoreDocLookupComparator that uses an internal lookup table of int.

Parameters:

termtext - The textual value of the term.

Returns:

An object representing termtext that sorts according to the natural order of termtext.

See Also:

Comparable, ScoreDocComparator