Package org.terrier.structures

Class Lexicon<KEY>

  • Type Parameters:
    KEY - the type of the key. Usually String to denote a term.
    All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable, java.lang.Iterable<java.util.Map.Entry<KEY,​LexiconEntry>>
    Direct Known Subclasses:
    MapLexicon, MultiLexicon
    public abstract class Lexicon<KEY>
extends java.lang.Object
implements java.io.Closeable, java.lang.Iterable<java.util.Map.Entry<KEY,​LexiconEntry>>
    A lexicon (a.k.a. dictionary, vocabulary) typically represents the list of terms 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. This class is an abstract class implementing a lexicon.
    Since:
    1.0.0
    Author:
    Craig Macdonald
    See Also:
    EntryStatistics, Pointer

    • Constructor Summary

      Constructors 
      Constructor Description
      Lexicon()  

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      abstract java.util.Map.Entry<KEY,​LexiconEntry> getIthLexiconEntry​(int index)
      Returns the term and LexiconEntry (containing statistics and a pointer) for the entry in the lexicon with the specified index.
      abstract java.util.Map.Entry<KEY,​LexiconEntry> getLexiconEntry​(int termid)
      Returns the term and LexiconEntry (containing statistics and a pointer) for the given term id.
      abstract LexiconEntry getLexiconEntry​(KEY term)
      Returns the LexiconEntry (containing statistics and a pointer) for the given term.
      abstract java.util.Iterator<java.util.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 terms 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

        forEach, iterator, spliterator

    • Constructor Detail

      • Lexicon

        public Lexicon()

    • Method Detail

      • numberOfEntries

        public abstract int numberOfEntries()
        Return the number of terms in the lexicon.
        Returns:
        the number of terms in the lexicon.

      • getLexiconEntry

        public abstract LexiconEntry getLexiconEntry​(KEY term)
        Returns the LexiconEntry (containing statistics and a pointer) for the given term. Returns null if the term is not present in the lexicon.
        Parameters:
        term - the key to lookup the lexicon with
        Returns:
        LexiconEntry for that term, or null if the term is not present in the lexicon.

      • getLexiconEntry

        public abstract java.util.Map.Entry<KEY,​LexiconEntry> getLexiconEntry​(int termid)
        Returns the term and LexiconEntry (containing statistics and a pointer) for the given term id. Throws NoSuchElementException is the termid is not found.
        Parameters:
        termid - the term id to lookup in the lexicon.
        Returns:
        the Map.Entry containing the term and the LexiconEntry.

      • getIthLexiconEntry

        public abstract java.util.Map.Entry<KEY,​LexiconEntry> getIthLexiconEntry​(int index)
        Returns the term and LexiconEntry (containing 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:
        the Map.Entry containing the term and the LexiconEntry.

      • getLexiconEntryRange

        public abstract java.util.Iterator<java.util.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:
        a Iterator over the set of Map.Entrys.