org.apache.lucene.util.automaton

## Class AutomatonTestUtil

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

-     public class AutomatonTestUtil
      extends Object

  Utilities for testing automata.

  Capable of generating random regular expressions, and automata, and also provides a number of very basic unoptimized implementations (*slow) for testing.

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `AutomatonTestUtil.RandomAcceptedStrings` Lets you retrieve random strings accepted by an Automaton.

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static int` | `DEFAULT_MAX_DETERMINIZED_STATES` Default maximum number of states that `Operations.determinize(org.apache.lucene.util.automaton.Automaton, int)` should create.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `AutomatonTestUtil()`

  - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static void` | `assertNoDetachedStates(Automaton a)` Checks that an automaton has no detached states that are unreachable from the initial state.
    `static Automaton` | `determinizeSimple(Automaton a)` Simple, original brics implementation of determinize()
    `static Automaton` | `determinizeSimple(Automaton a, Set<Integer> initialset)` Simple, original brics implementation of determinize() Determinizes the given automaton using the given set of initial states.
    `static Set<IntsRef>` | `getFiniteStringsRecursive(Automaton a, int limit)` Simple, original implementation of getFiniteStrings.
    `static boolean` | `isDeterministicSlow(Automaton a)` Returns true if the automaton is deterministic.
    `static boolean` | `isFiniteSlow(Automaton a)` Returns true if the language of this automaton is finite.
    `static Automaton` | `minimizeSimple(Automaton a)` Simple, original brics implementation of Brzozowski minimize()
    `static Automaton` | `randomAutomaton(Random random)` return a random NFA/DFA for testing
    `static String` | `randomRegexp(Random r)` Returns random string, including full unicode range.

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

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

- - ### Field Detail

    - #### DEFAULT_MAX_DETERMINIZED_STATES

          public static final int DEFAULT_MAX_DETERMINIZED_STATES

      Default maximum number of states that `Operations.determinize(org.apache.lucene.util.automaton.Automaton, int)` should create.
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### AutomatonTestUtil

          public AutomatonTestUtil()

  - ### Method Detail

    - #### randomRegexp

          public static String randomRegexp(Random r)

      Returns random string, including full unicode range.

    - #### randomAutomaton

          public static Automaton randomAutomaton(Random random)

      return a random NFA/DFA for testing

    - #### minimizeSimple

          public static Automaton minimizeSimple(Automaton a)

      Simple, original brics implementation of Brzozowski minimize()

    - #### determinizeSimple

          public static Automaton determinizeSimple(Automaton a)

      Simple, original brics implementation of determinize()

    - #### determinizeSimple

          public static Automaton determinizeSimple(Automaton a,
                                                    Set<Integer> initialset)

      Simple, original brics implementation of determinize() Determinizes the given automaton using the given set of initial states.

    - #### getFiniteStringsRecursive

          public static Set<IntsRef> getFiniteStringsRecursive(Automaton a,
                                                               int limit)

      Simple, original implementation of getFiniteStrings.

      Returns the set of accepted strings, assuming that at most `limit` strings are accepted. If more than `limit` strings are accepted, the first limit strings found are returned. If `limit`<0, then the limit is infinite.

      This implementation is recursive: it uses one stack frame for each digit in the returned strings (ie, max is the max length returned string).

    - #### isFiniteSlow

          public static boolean isFiniteSlow(Automaton a)

      Returns true if the language of this automaton is finite.

      WARNING: this method is slow, it will blow up if the automaton is large. this is only used to test the correctness of our faster implementation.

    - #### assertNoDetachedStates

          public static void assertNoDetachedStates(Automaton a)

      Checks that an automaton has no detached states that are unreachable from the initial state.

    - #### isDeterministicSlow

          public static boolean isDeterministicSlow(Automaton a)

      Returns true if the automaton is deterministic.

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