org.apache.lucene.search.spell

Class SpellChecker

public class SpellChecker extends Object

Spell Checker class (Main class)
(initially inspired by the David Spencer code).

Example Usage:

  SpellChecker spellchecker = new SpellChecker(spellIndexDirectory);
  // To index a field of a user index:
  spellchecker.indexDictionary(new LuceneDictionary(my_lucene_reader, a_field));
  // To index a file containing words:
  spellchecker.indexDictionary(new PlainTextDictionary(new File("myfile.txt")));
  String[] suggestions = spellchecker.suggestSimilar("misspelt", 5);
 

Version: 1.0

Author: Nicolas Maisonneuve

Field Summary
static StringF_WORD
Field name for each word in the ngram index.
Constructor Summary
SpellChecker(Directory spellIndex)
Use the given directory as a spell checker index.
Method Summary
voidclearIndex()
Removes all terms from the spell check index.
booleanexist(String word)
Check whether the word exists in the index.
protected voidfinalize()
Closes the internal IndexReader.
voidindexDictionary(Dictionary dict)
Index a Dictionary
voidsetAccuracy(float minScore)
Sets the accuracy 0 < minScore < 1; default 0.5
voidsetSpellIndex(Directory spellIndex)
Use a different index as the spell checker index or re-open the existing index if spellIndex is the same value as given in the constructor.
String[]suggestSimilar(String word, int numSug)
Suggest similar words.
String[]suggestSimilar(String word, int numSug, IndexReader ir, String field, boolean morePopular)
Suggest similar words (optionally restricted to a field of an index).

Field Detail

F_WORD

public static final String F_WORD
Field name for each word in the ngram index.

Constructor Detail

SpellChecker

public SpellChecker(Directory spellIndex)
Use the given directory as a spell checker index. The directory is created if it doesn't exist yet.

Parameters: spellIndex

Throws: IOException

Method Detail

clearIndex

public void clearIndex()
Removes all terms from the spell check index.

Throws: IOException

exist

public boolean exist(String word)
Check whether the word exists in the index.

Parameters: word

Returns: true iff the word exists in the index

Throws: IOException

finalize

protected void finalize()
Closes the internal IndexReader.

indexDictionary

public void indexDictionary(Dictionary dict)
Index a Dictionary

Parameters: dict the dictionary to index

Throws: IOException

setAccuracy

public void setAccuracy(float minScore)
Sets the accuracy 0 < minScore < 1; default 0.5

setSpellIndex

public void setSpellIndex(Directory spellIndex)
Use a different index as the spell checker index or re-open the existing index if spellIndex is the same value as given in the constructor.

Parameters: spellIndex

Throws: IOException

suggestSimilar

public String[] suggestSimilar(String word, int numSug)
Suggest similar words.

As the Lucene similarity that is used to fetch the most relevant n-grammed terms is not the same as the edit distance strategy used to calculate the best matching spell-checked word from the hits that Lucene found, one usually has to retrieve a couple of numSug's in order to get the true best match.

I.e. if numSug == 1, don't count on that suggestion being the best one. Thus, you should set this value to at least 5 for a good suggestion.

Parameters: word the word you want a spell check done on numSug the number of suggested words

Returns: String[]

Throws: IOException

suggestSimilar

public String[] suggestSimilar(String word, int numSug, IndexReader ir, String field, boolean morePopular)
Suggest similar words (optionally restricted to a field of an index).

As the Lucene similarity that is used to fetch the most relevant n-grammed terms is not the same as the edit distance strategy used to calculate the best matching spell-checked word from the hits that Lucene found, one usually has to retrieve a couple of numSug's in order to get the true best match.

I.e. if numSug == 1, don't count on that suggestion being the best one. Thus, you should set this value to at least 5 for a good suggestion.

Parameters: word the word you want a spell check done on numSug the number of suggested words ir the indexReader of the user index (can be null see field param) field the field of the user index: if field is not null, the suggested words are restricted to the words present in this field. morePopular return only the suggest words that are more frequent than the searched word (only if restricted mode = (indexReader!=null and field!=null)

Returns: String[] the sorted list of the suggest words with these 2 criteria: first criteria: the edit distance, second criteria (only if restricted mode): the popularity of the suggest words in the field of the user index

Throws: IOException

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