org.apache.lucene.util.automaton

## Class LevenshteinAutomata

- java.lang.Object
- - org.apache.lucene.util.automaton.LevenshteinAutomata

-     public class LevenshteinAutomata
      extends Object

  Class to construct DFAs that match a word within some edit distance.

  Implements the algorithm described in: Schulz and Mihov: Fast String Correction with Levenshtein Automata

  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static int` | `MAXIMUM_SUPPORTED_DISTANCE` Maximum edit distance this class can generate an automaton for.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `LevenshteinAutomata(int[] word, int alphaMax, boolean withTranspositions)` Expert: specify a custom maximum possible symbol (alphaMax); default is Character.MAX_CODE_POINT.
    `LevenshteinAutomata(String input, boolean withTranspositions)` Create a new LevenshteinAutomata for some input String.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `Automaton` | `toAutomaton(int n)` Compute a DFA that accepts all strings within an edit distance of `n`.
    `Automaton` | `toAutomaton(int n, String prefix)` Compute a DFA that accepts all strings within an edit distance of `n`, matching the specified exact prefix.

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

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

- - ### Field Detail

    - #### MAXIMUM_SUPPORTED_DISTANCE

          public static final int MAXIMUM_SUPPORTED_DISTANCE

      Maximum edit distance this class can generate an automaton for.
      See Also:
        Constant Field Values
      NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

  - ### Constructor Detail

    - #### LevenshteinAutomata

          public LevenshteinAutomata(String input,
                                     boolean withTranspositions)

      Create a new LevenshteinAutomata for some input String. Optionally count transpositions as a primitive edit.

    - #### LevenshteinAutomata

          public LevenshteinAutomata(int[] word,
                                     int alphaMax,
                                     boolean withTranspositions)

      Expert: specify a custom maximum possible symbol (alphaMax); default is Character.MAX_CODE_POINT.

  - ### Method Detail

    - #### toAutomaton

          public Automaton toAutomaton(int n)

      Compute a DFA that accepts all strings within an edit distance of `n`.

      All automata have the following properties:

      - They are deterministic (DFA).
      - There are no transitions to dead states.
      - They are not minimal (some transitions could be combined).

    - #### toAutomaton

          public Automaton toAutomaton(int n,
                                       String prefix)

      Compute a DFA that accepts all strings within an edit distance of `n`, matching the specified exact prefix.

      All automata have the following properties:

      - They are deterministic (DFA).
      - There are no transitions to dead states.
      - They are not minimal (some transitions could be combined).

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