org.apache.commons.text.similarity

Class LevenshteinDetailedDistance

java.lang.Object

org.apache.commons.text.similarity.LevenshteinDetailedDistance

All Implemented Interfaces:

EditDistance<LevenshteinResults>, SimilarityScore<LevenshteinResults>

public class LevenshteinDetailedDistance
extends Object
implements EditDistance<LevenshteinResults>

An algorithm for measuring the difference between two character sequences.

This is the number of changes needed to change one sequence into another, where each change is a single character modification (deletion, insertion or substitution).

Since:

1.0

Constructor Summary

Constructors

Constructor and Description
LevenshteinDetailedDistance() This returns the default instance that uses a version of the algorithm that does not use a threshold parameter.
LevenshteinDetailedDistance(Integer threshold) If the threshold is not null, distance calculations will be limited to a maximum length.

Method Summary

Modifier and Type	Method and Description
LevenshteinResults	apply(CharSequence left, CharSequence right) Find the Levenshtein distance between two Strings.
static LevenshteinDetailedDistance	getDefaultInstance() Gets the default instance.
Integer	getThreshold() Gets the distance threshold.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LevenshteinDetailedDistance

public LevenshteinDetailedDistance()

This returns the default instance that uses a version of the algorithm that does not use a threshold parameter.

See Also:

getDefaultInstance()

LevenshteinDetailedDistance

public LevenshteinDetailedDistance(Integer threshold)

If the threshold is not null, distance calculations will be limited to a maximum length.

If the threshold is null, the unlimited version of the algorithm will be used.

Parameters:

threshold - If this is null then distances calculations will not be limited. This may not be negative.

Method Detail

apply

public LevenshteinResults apply(CharSequence left,
                                CharSequence right)

Find the Levenshtein distance between two Strings.

A higher score indicates a greater distance.

The previous implementation of the Levenshtein distance algorithm was from http://www.merriampark.com/ld.htm

Chas Emerick has written an implementation in Java, which avoids an OutOfMemoryError which can occur when my Java implementation is used with very large strings.
This implementation of the Levenshtein distance algorithm is from http://www.merriampark.com/ldjava.htm

 distance.apply(null, *)             = IllegalArgumentException
 distance.apply(*, null)             = IllegalArgumentException
 distance.apply("","")               = 0
 distance.apply("","a")              = 1
 distance.apply("aaapppp", "")       = 7
 distance.apply("frog", "fog")       = 1
 distance.apply("fly", "ant")        = 3
 distance.apply("elephant", "hippo") = 7
 distance.apply("hippo", "elephant") = 7
 distance.apply("hippo", "zzzzzzzz") = 8
 distance.apply("hello", "hallo")    = 1
 

Specified by:

apply in interface EditDistance<LevenshteinResults>

Specified by:

apply in interface SimilarityScore<LevenshteinResults>

Parameters:

left - the first string, must not be null

right - the second string, must not be null

Returns:

result distance, or -1

Throws:

IllegalArgumentException - if either String input null

getDefaultInstance

public static LevenshteinDetailedDistance getDefaultInstance()

Gets the default instance.

Returns:

the default instace

getThreshold

public Integer getThreshold()

Gets the distance threshold.

Returns:

the distance threshold