Package org.apache.lucene.search.spell

# Class NGramDistance

java.lang.Object
org.apache.lucene.search.spell.NGramDistance

All Implemented Interfaces:
  `StringDistance`

public class NGramDistance extends Object implements StringDistance
N-Gram version of edit distance based on paper by Grzegorz Kondrak, "N-gram similarity and distance". Proceedings of the Twelfth International Conference on String Processing and Information Retrieval (SPIRE 2005), pp. 115-126, Buenos Aires, Argentina, November 2005. http://www.cs.ualberta.ca/~kondrak/papers/spire05.pdf

This implementation uses the position-based optimization to compute partial matches of n-gram sub-strings and adds a null-character prefix of size n-1 so that the first character is contained in the same number of n-grams as a middle character. Null-character prefix matches are discounted so that strings with no matching characters will return a distance of 0.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `NGramDistance()`
  Creates an N-Gram distance measure using n-grams of size 2.
  `NGramDistance(int size)`
  Creates an N-Gram distance measure using n-grams of the specified size.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `equals(Object obj)`
  `float`
  `getDistance(String source, String target)`
  Returns a float between 0 and 1 based on how similar the specified strings are to one another.
  `int`
  `hashCode()`
  `String`
  `toString()`

  ### Methods inherited from class java.lang.Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### NGramDistance

    public NGramDistance(int size)
    Creates an N-Gram distance measure using n-grams of the specified size.
    Parameters:
      `size` - The size of the n-gram to be used to compute the string distance.

  - ### NGramDistance

    public NGramDistance()
    Creates an N-Gram distance measure using n-grams of size 2.

- ## Method Details

  - ### getDistance

    public float getDistance(String source, String target)
    Description copied from interface: `StringDistance`
    Returns a float between 0 and 1 based on how similar the specified strings are to one another. Returning a value of 1 means the specified strings are identical and 0 means the string are maximally different.
    Specified by:
      `getDistance` in interface `StringDistance`
    Parameters:
      `source` - The first string.
      `target` - The second string.
    Returns:
      a float between 0 and 1 based on how similar the specified strings are to one another.

  - ### hashCode

    public int hashCode()
    Overrides:
      `hashCode` in class `Object`

  - ### equals

    public boolean equals(Object obj)
    Overrides:
      `equals` in class `Object`

  - ### toString

    public String toString()
    Overrides:
      `toString` in class `Object`