org.terrier.structures

Class Lexicon<KEY>

java.lang.Object

org.terrier.structures.Lexicon<KEY>

Type Parameters:

KEY - the type of the key. Usually String to denote a term.

All Implemented Interfaces:

Closeable, AutoCloseable, Iterable<Map.Entry<KEY,LexiconEntry>>

Direct Known Subclasses:

MapLexicon, MultiLexicon

public abstract class Lexicon<KEY>
extends Object
implements Closeable, Iterable<Map.Entry<KEY,LexiconEntry>>

Abstract Lexicon implementation. The Lexicon class typically represents the list of terms (dictionary) in the index, together with their statistics (see EntryStatistics) and the pointer (Pointer) to the offset of that term's postings in the PostingIndex returned by Index.getInvertedIndex(). The EntryStatistics and Pointer are combined in a single LexiconEntry object.

Since:

1.0.0

Author:

Craig Macdonald

See Also:

EntryStatistics, Pointer

Constructor Summary

Constructors

Constructor and Description
Lexicon()

Method Summary

Methods

Modifier and Type	Method and Description
abstract Map.Entry<KEY,LexiconEntry>	getIthLexiconEntry(int index) Get the term and LexiconEntry (contains statistics and a pointer) for the entry in the lexicon with the specified index.
abstract Map.Entry<KEY,LexiconEntry>	getLexiconEntry(int termid) Get the term and LexiconEntry (contains statistics and a pointer) for a given term id.
abstract LexiconEntry	getLexiconEntry(KEY term) Get the LexiconEntry (contains statistics and a pointer) for the given term.
abstract Iterator<Map.Entry<KEY,LexiconEntry>>	getLexiconEntryRange(KEY from, KEY to) Returns an iterator over a set of LexiconEntries within a range of entries in the lexicon.
abstract int	numberOfEntries() Return the number of entries in the lexicon

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.io.Closeable

close

Methods inherited from interface java.lang.Iterable

iterator

Constructor Detail

Lexicon

public Lexicon()

Method Detail

numberOfEntries

public abstract int numberOfEntries()

Return the number of entries in the lexicon

getLexiconEntry

public abstract LexiconEntry getLexiconEntry(KEY term)

Get the LexiconEntry (contains statistics and a pointer) for the given term. Returns null if the term is not found in the lexicon.

Parameters:

term - key to lookup the lexicon with

Returns:

LexiconEntry for that term, or null if not found

getLexiconEntry

public abstract Map.Entry<KEY,LexiconEntry> getLexiconEntry(int termid)

Get the term and LexiconEntry (contains statistics and a pointer) for a given term id. Throws NoSuchElementException is the termid is not found.

Parameters:

termid - the term id to lookup in the lexicon

Returns:

Map.Entry tuple containing the term and the LexiconEntry

getIthLexiconEntry

public abstract Map.Entry<KEY,LexiconEntry> getIthLexiconEntry(int index)

Get the term and LexiconEntry (contains statistics and a pointer) for the entry in the lexicon with the specified index. Throws NoSuchElementException is the termid is not found.

Parameters:

index - the entry number to lookup in the lexicon

Returns:

Map.Entry tuple containing the term and the LexiconEntry

getLexiconEntryRange

public abstract Iterator<Map.Entry<KEY,LexiconEntry>> getLexiconEntryRange(KEY from,
                                                         KEY to)

Returns an iterator over a set of LexiconEntries within a range of entries in the lexicon.

Parameters:

from - low endpoint term in the subset, inclusive.

to - high endpoint term in the subset, exclusive.

Returns:

Iterator over the set.