NGramDistance (Lucene 3.6.2 API)

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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
`float`	`getDistance(String source, String target)`	Returns a float between 0 and 1 based on how similar the specified strings are to one another.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, 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.

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