Automaton (Lucene 4.0.0 API)

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

All Implemented Interfaces:

Cloneable
```
public class Automaton
extends Object
implements Cloneable
```
Finite-state automaton with regular expression operations.
Class invariants:
- An automaton is either represented explicitly (with State and Transition objects) or with a singleton string (see getSingleton() and expandSingleton()) in case the automaton is known to accept exactly one string. (Implicitly, all states and transitions of an automaton are reachable from its initial state.)
- Automata are always reduced (see reduce()) and have no transitions to dead states (see removeDeadTransitions()).
- If an automaton is nondeterministic, then isDeterministic() returns false (but the converse is not required).
- Automata provided as input to operations are generally assumed to be disjoint.
If the states or transitions are manipulated manually, the restoreInvariant() and setDeterministic(boolean) methods should be used afterwards to restore representation invariants that are assumed by the built-in automata operations.

Note: This class has internal mutable state and is not thread safe. It is the caller's responsibility to ensure any necessary synchronization if you wish to use the same Automaton from multiple threads. In general it is instead recommended to use a RunAutomaton for multithreaded matching: it is immutable, thread safe, and much faster.
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 MINIMIZE_HOPCROFT
Minimize using Hopcroft's O(n log n) algorithm.

Fields
Modifier and Type	Field and Description
`static int`	`MINIMIZE_HOPCROFT` Minimize using Hopcroft's O(n log n) algorithm.

Constructor Summary

Constructors
Constructor and Description

Automaton()

Automaton(State initial)
Constructs a new automaton that accepts the empty language.

Constructors
Constructor and Description
`Automaton()`
`Automaton(State initial)` Constructs a new automaton that accepts the empty language.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`clearNumberedStates()`
`Automaton`	`clone()` Returns a clone of this automaton.
`Automaton`	`complement()` See `BasicOperations.complement(Automaton)`.
`Automaton`	`concatenate(Automaton a)` See `BasicOperations.concatenate(Automaton, Automaton)`.
`static Automaton`	`concatenate(List<Automaton> l)` See `BasicOperations.concatenate(List)`.
`void`	`determinize()` See `BasicOperations.determinize(Automaton)`.
`boolean`	`equals(Object obj)`
`void`	`expandSingleton()` Expands singleton representation to normal representation.
`Set<State>`	`getAcceptStates()` Returns the set of reachable accept states.
`Object`	`getInfo()` Returns extra information associated with this automaton.
`State`	`getInitialState()` Gets initial state.
`State[]`	`getNumberedStates()`
`int`	`getNumberOfStates()` Returns the number of states in this automaton.
`int`	`getNumberOfTransitions()` Returns the number of transitions in this automaton.
`String`	`getSingleton()` Returns the singleton string for this automaton.
`Transition[][]`	`getSortedTransitions()` Returns a sorted array of transitions for each state (and sets state numbers).
`int`	`hashCode()`
`Automaton`	`intersection(Automaton a)` See `BasicOperations.intersection(Automaton, Automaton)`.
`boolean`	`isDeterministic()` Returns deterministic flag for this automaton.
`boolean`	`isEmptyString()` See `BasicOperations.isEmptyString(Automaton)`.
`static Automaton`	`minimize(Automaton a)` See `MinimizationOperations.minimize(Automaton)`.
`Automaton`	`minus(Automaton a)` See `BasicOperations.minus(Automaton, Automaton)`.
`Automaton`	`optional()` See `BasicOperations.optional(Automaton)`.
`void`	`reduce()` Reduces this automaton.
`void`	`removeDeadTransitions()` Removes transitions to dead states and calls `reduce()`.
`Automaton`	`repeat()` See `BasicOperations.repeat(Automaton)`.
`Automaton`	`repeat(int min)` See `BasicOperations.repeat(Automaton, int)`.
`Automaton`	`repeat(int min, int max)` See `BasicOperations.repeat(Automaton, int, int)`.
`void`	`restoreInvariant()` Restores representation invariant.
`static boolean`	`setAllowMutate(boolean flag)` Sets or resets allow mutate flag.
`void`	`setDeterministic(boolean deterministic)` Sets deterministic flag for this automaton.
`void`	`setInfo(Object info)` Associates extra information with this automaton.
`static void`	`setMinimization(int algorithm)` Selects minimization algorithm (default: `MINIMIZE_HOPCROFT`).
`static void`	`setMinimizeAlways(boolean flag)` Sets or resets minimize always flag.
`void`	`setNumberedStates(State[] states)`
`void`	`setNumberedStates(State[] states, int count)`
`boolean`	`subsetOf(Automaton a)` See `BasicOperations.subsetOf(Automaton, Automaton)`.
`String`	`toDot()` Returns Graphviz Dot representation of this automaton.
`String`	`toString()` Returns a string representation of this automaton.
`Automaton`	`union(Automaton a)` See `BasicOperations.union(Automaton, Automaton)`.
`static Automaton`	`union(Collection<Automaton> l)` See `BasicOperations.union(Collection)`.

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - MINIMIZE_HOPCROFT
```
public static final int MINIMIZE_HOPCROFT
```
    Minimize using Hopcroft's O(n log n) algorithm. This is regarded as one of the most generally efficient algorithms that exist.
    
    See Also:
    setMinimization(int), Constant Field Values
- Constructor Detail
  - Automaton
```
public Automaton(State initial)
```
    Constructs a new automaton that accepts the empty language. Using this constructor, automata can be constructed manually from State and Transition objects.
    
    See Also:
    State, Transition
  - Automaton
```
public Automaton()
```
- Method Detail
  - setMinimization
```
public static void setMinimization(int algorithm)
```
    Selects minimization algorithm (default: MINIMIZE_HOPCROFT).
    
    Parameters:
    algorithm - minimization algorithm
  - setMinimizeAlways
```
public static void setMinimizeAlways(boolean flag)
```
    Sets or resets minimize always flag. If this flag is set, then MinimizationOperations.minimize(Automaton) will automatically be invoked after all operations that otherwise may produce non-minimal automata. By default, the flag is not set.
    
    Parameters:
    flag - if true, the flag is set
  - setAllowMutate
```
public static boolean setAllowMutate(boolean flag)
```
    Sets or resets allow mutate flag. If this flag is set, then all automata operations may modify automata given as input; otherwise, operations will always leave input automata languages unmodified. By default, the flag is not set.
    
    Parameters:
    flag - if true, the flag is set
    
    Returns:
    previous value of the flag
  - getSingleton
```
public String getSingleton()
```
    Returns the singleton string for this automaton. An automaton that accepts exactly one string may be represented in singleton mode. In that case, this method may be used to obtain the string.
    
    Returns:
    string, null if this automaton is not in singleton mode.
  - getInitialState
```
public State getInitialState()
```
    Gets initial state.
    
    Returns:
    state
  - isDeterministic
```
public boolean isDeterministic()
```
    Returns deterministic flag for this automaton.
    
    Returns:
    true if the automaton is definitely deterministic, false if the automaton may be nondeterministic
  - setDeterministic
```
public void setDeterministic(boolean deterministic)
```
    Sets deterministic flag for this automaton. This method should (only) be used if automata are constructed manually.
    
    Parameters:
    deterministic - true if the automaton is definitely deterministic, false if the automaton may be nondeterministic
  - setInfo
```
public void setInfo(Object info)
```
    Associates extra information with this automaton.
    
    Parameters:
    info - extra information
  - getInfo
```
public Object getInfo()
```
    Returns extra information associated with this automaton.
    
    Returns:
    extra information
    See Also:
    setInfo(Object)
  - getNumberedStates
```
public State[] getNumberedStates()
```
  - setNumberedStates
```
public void setNumberedStates(State[] states)
```
  - setNumberedStates
```
public void setNumberedStates(State[] states,
                     int count)
```
  - clearNumberedStates
```
public void clearNumberedStates()
```
  - getAcceptStates
```
public Set<State> getAcceptStates()
```
    Returns the set of reachable accept states.
    
    Returns:
    set of State objects
  - restoreInvariant
```
public void restoreInvariant()
```
    Restores representation invariant. This method must be invoked before any built-in automata operation is performed if automaton states or transitions are manipulated manually.
    
    See Also:
    setDeterministic(boolean)
  - reduce
```
public void reduce()
```
    Reduces this automaton. An automaton is "reduced" by combining overlapping and adjacent edge intervals with same destination.
  - removeDeadTransitions
```
public void removeDeadTransitions()
```
    Removes transitions to dead states and calls reduce(). (A state is "dead" if no accept state is reachable from it.)
  - getSortedTransitions
```
public Transition[][] getSortedTransitions()
```
    Returns a sorted array of transitions for each state (and sets state numbers).
  - expandSingleton
```
public void expandSingleton()
```
    Expands singleton representation to normal representation. Does nothing if not in singleton representation.
  - getNumberOfStates
```
public int getNumberOfStates()
```
    Returns the number of states in this automaton.
  - getNumberOfTransitions
```
public int getNumberOfTransitions()
```
    Returns the number of transitions in this automaton. This number is counted as the total number of edges, where one edge may be a character interval.
  - equals
```
public boolean equals(Object obj)
```
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    Returns a string representation of this automaton.
    
    Overrides:
    
    toString in class Object
  - toDot
```
public String toDot()
```
    Returns Graphviz Dot representation of this automaton.
  - clone
```
public Automaton clone()
```
    Returns a clone of this automaton.
    
    Overrides:
    
    clone in class Object
  - concatenate
```
public Automaton concatenate(Automaton a)
```
    See BasicOperations.concatenate(Automaton, Automaton).
  - concatenate
```
public static Automaton concatenate(List<Automaton> l)
```
    See BasicOperations.concatenate(List).
  - optional
```
public Automaton optional()
```
    See BasicOperations.optional(Automaton).
  - repeat
```
public Automaton repeat()
```
    See BasicOperations.repeat(Automaton).
  - repeat
```
public Automaton repeat(int min)
```
    See BasicOperations.repeat(Automaton, int).
  - repeat
```
public Automaton repeat(int min,
               int max)
```
    See BasicOperations.repeat(Automaton, int, int).
  - complement
```
public Automaton complement()
```
    See BasicOperations.complement(Automaton).
  - minus
```
public Automaton minus(Automaton a)
```
    See BasicOperations.minus(Automaton, Automaton).
  - intersection
```
public Automaton intersection(Automaton a)
```
    See BasicOperations.intersection(Automaton, Automaton).
  - subsetOf
```
public boolean subsetOf(Automaton a)
```
    See BasicOperations.subsetOf(Automaton, Automaton).
  - union
```
public Automaton union(Automaton a)
```
    See BasicOperations.union(Automaton, Automaton).
  - union
```
public static Automaton union(Collection<Automaton> l)
```
    See BasicOperations.union(Collection).
  - determinize
```
public void determinize()
```
    See BasicOperations.determinize(Automaton).
  - isEmptyString
```
public boolean isEmptyString()
```
    See BasicOperations.isEmptyString(Automaton).
  - minimize
```
public static Automaton minimize(Automaton a)
```
    See MinimizationOperations.minimize(Automaton). Returns the automaton being given as argument.

Class Automaton

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MINIMIZE_HOPCROFT

Constructor Detail

Automaton

Automaton

Method Detail

setMinimization

setMinimizeAlways

setAllowMutate

getSingleton

getInitialState

isDeterministic

setDeterministic

setInfo

getInfo

getNumberedStates

setNumberedStates

setNumberedStates

clearNumberedStates

getAcceptStates

restoreInvariant

reduce

removeDeadTransitions

getSortedTransitions

expandSingleton

getNumberOfStates

getNumberOfTransitions

equals

hashCode

toString

toDot

clone

concatenate

concatenate

optional

repeat

repeat

repeat

complement

minus

intersection

subsetOf

union

union

determinize

isEmptyString

minimize