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

    All Methods Instance Methods Concrete Methods
    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 Detail

    - #### 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 Detail

    - #### 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`