io.prestosql.execution

Class StateMachine<T>

java.lang.Object

io.prestosql.execution.StateMachine<T>

@ThreadSafe
public class StateMachine<T>
extends Object

Simple state machine which holds a single state. Callers can register for state change events.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	StateMachine.StateChangeListener<T>

Constructor Summary

Constructors

Constructor and Description
StateMachine(String name, Executor executor, T initialState) Creates a state machine with the specified initial state and no terminal states.
StateMachine(String name, Executor executor, T initialState, Iterable<T> terminalStates) Creates a state machine with the specified initial state and terminal states.

Method Summary

Modifier and Type	Method and Description
void	addStateChangeListener(StateMachine.StateChangeListener<T> stateChangeListener) Adds a listener to be notified when the state instance changes according to .equals().
boolean	compareAndSet(T expectedState, T newState) Sets the state if the current state .equals() the specified expected state.
T	get()
com.google.common.util.concurrent.ListenableFuture<T>	getStateChange(T currentState) Gets a future that completes when the state is no longer .equals() to currentState).
T	set(T newState) Sets the state.
boolean	setIf(T newState, Predicate<T> predicate) Sets the state if the current state satisfies the specified predicate.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

StateMachine

public StateMachine(String name,
                    Executor executor,
                    T initialState)

Creates a state machine with the specified initial state and no terminal states.

Parameters:

name - name of this state machine to use in debug statements

executor - executor for firing state change events; must not be a same thread executor

initialState - the initial state

StateMachine

public StateMachine(String name,
                    Executor executor,
                    T initialState,
                    Iterable<T> terminalStates)

Creates a state machine with the specified initial state and terminal states.

Parameters:

name - name of this state machine to use in debug statements

executor - executor for firing state change events; must not be a same thread executor

initialState - the initial state

terminalStates - the terminal states

Method Detail

get

public T get()

set

public T set(T newState)

Sets the state. If the new state does not .equals() the current state, listeners and waiters will be notified.

Returns:

the old state

setIf

public boolean setIf(T newState,
                     Predicate<T> predicate)

Sets the state if the current state satisfies the specified predicate. If the new state does not .equals() the current state, listeners and waiters will be notified.

Returns:

true if the state is set

compareAndSet

public boolean compareAndSet(T expectedState,
                             T newState)

Sets the state if the current state .equals() the specified expected state. If the new state does not .equals() the current state, listeners and waiters will be notified.

Returns:

true if the state is set

getStateChange

public com.google.common.util.concurrent.ListenableFuture<T> getStateChange(T currentState)

Gets a future that completes when the state is no longer .equals() to currentState).

addStateChangeListener

public void addStateChangeListener(StateMachine.StateChangeListener<T> stateChangeListener)

Adds a listener to be notified when the state instance changes according to .equals(). Listener is always notified asynchronously using a dedicated notification thread pool so, care should be taken to avoid leaking this when adding a listener in a constructor. Additionally, it is possible notifications are observed out of order due to the asynchronous execution. The listener is immediately notified immediately of the current state.

toString

public String toString()

Overrides:

toString in class Object