Package org.apache.tinkerpop.gremlin.process.traversal.util

Class EmptyTraversal<S,E>

java.lang.Object

org.apache.tinkerpop.gremlin.process.traversal.util.EmptyTraversal<S,E>

All Implemented Interfaces:

Serializable, AutoCloseable, Cloneable, Iterator<E>, Traversal<S,E>, Traversal.Admin<S,E>

public final class EmptyTraversal<S,E>
extends Object
implements Traversal.Admin<S,E>

Author:

Marko A. Rodriguez (http://markorodriguez.com)

See Also:

• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.tinkerpop.gremlin.process.traversal.Traversal

Traversal.Admin<S,E>, Traversal.Exceptions, Traversal.Symbols

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	EmptyTraversal()

Method Summary

Modifier and Type	Method	Description
void	addStart(Traverser.Admin<S> start)	Add a single Traverser.Admin object to the head of the traversal.
void	addStarts(Iterator<Traverser.Admin<S>> starts)	Add an iterator of Traverser.Admin objects to the head/start of the traversal.
<S2, E2> Traversal.Admin<S2,E2>	addStep(int index, Step<?,?> step)	Add a Step to an arbitrary point in the traversal.
<E2> Traversal.Admin<S,E2>	addStep(Step<?,E2> step)	Add a Step to the end of the traversal.
void	applyStrategies()	Apply the registered TraversalStrategies to the traversal.
Traversal.Admin<S,E>	asAdmin()	Get access to administrative methods of the traversal via its accompanying Traversal.Admin.
EmptyTraversal<S,E>	clone()	Cloning is used to duplicate the traversal typically in OLAP environments.
boolean	equals(Object object)
Optional<Graph>	getGraph()	Gets the Graph instance associated directly to this Traversal or through its parent.
GremlinLang	getGremlinLang()	Get the GremlinLang associated with the construction of this traversal.
GValueManager	getGValueManager()	Get the GValueManager associated with this traversal.
TraversalParent	getParent()	Get the TraversalParent Step that is the parent of this traversal.
TraversalSideEffects	getSideEffects()	Get the TraversalSideEffects associated with the traversal.
List<Step>	getSteps()	Get the Step instances associated with this traversal.
TraversalStrategies	getStrategies()	Get the TraversalStrategies associated with this traversal.
TraverserGenerator	getTraverserGenerator()	Get the TraverserGenerator associated with this traversal.
Set<TraverserRequirement>	getTraverserRequirements()	Get the set of all TraverserRequirements for this traversal.
int	hashCode()
boolean	hasNext()
static <A, B> EmptyTraversal<A,B>	instance()
boolean	isLocked()	When the traversal has had its TraversalStrategies applied to it, it is locked.
void	lock()	Lock the traversal and perform any final adjustments to it after strategy application.
E	next()
<S2, E2> Traversal.Admin<S2,E2>	removeStep(int index)	Remove a Step from the traversal.
void	setGraph(Graph graph)
void	setGValueManager(GValueManager gValueManager)	Set the GValueManager associated with this traversal.
void	setParent(TraversalParent step)	Set the TraversalParent Step that is the parent of this traversal.
void	setSideEffects(TraversalSideEffects sideEffects)	Set the TraversalSideEffects of this traversal.
void	setStrategies(TraversalStrategies traversalStrategies)	Set the TraversalStrategies to be used by this traversal at evaluation time.

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Iterator

remove

Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.Traversal

close, discard, explain, fill, forEachRemaining, forEachRemaining, iterate, next, notifyClose, profile, promise, toBulkSet, toList, toSet, toStream, tryNext

Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.Traversal.Admin

equals, getEndStep, getStartStep, getTraversalSource, getTraverserSetSupplier, isRoot, nextTraverser, removeStep, reset

Constructor Details

EmptyTraversal

protected EmptyTraversal()

Method Details

instance

public static <A,
B> EmptyTraversal<A,B> instance()

getGremlinLang

public GremlinLang getGremlinLang()

Description copied from interface: Traversal.Admin

Get the GremlinLang associated with the construction of this traversal.

Specified by:

getGremlinLang in interface Traversal.Admin<S,E>

Returns:

the byte code representation of the traversal

getGValueManager

public GValueManager getGValueManager()

Description copied from interface: Traversal.Admin

Get the GValueManager associated with this traversal.

Specified by:

getGValueManager in interface Traversal.Admin<S,E>

setGValueManager

public void setGValueManager(GValueManager gValueManager)

Description copied from interface: Traversal.Admin

Set the GValueManager associated with this traversal.

Specified by:

setGValueManager in interface Traversal.Admin<S,E>

asAdmin

public Traversal.Admin<S,E> asAdmin()

Description copied from interface: Traversal

Get access to administrative methods of the traversal via its accompanying Traversal.Admin.

Specified by:

asAdmin in interface Traversal<S,E>

Returns:

the admin of this traversal

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<S>

next

public E next()

Specified by:

next in interface Iterator<S>

getSideEffects

public TraversalSideEffects getSideEffects()

Description copied from interface: Traversal.Admin

Get the TraversalSideEffects associated with the traversal. This method should not be called externally for purposes of retrieving side-effects as traversal results. Traversal results should only be returned by way of the execution of the traversal itself. Should a side-effect of a traversal be needed it should only be obtained by using GraphTraversal.cap(String, String...) so that the side-effect can be included as part of the traversal iteration. Relying on this method to get side-effects in these situations may not result in consistent behavior across all types of executions and environments (e.g. remoting).

Specified by:

getSideEffects in interface Traversal.Admin<S,E>

Returns:

The traversal sideEffects

applyStrategies

public void applyStrategies()

Description copied from interface: Traversal.Admin

Apply the registered TraversalStrategies to the traversal. Once the strategies are applied, the traversal is "locked" and can no longer have steps added to it. The order of operations for strategy applications should be: globally id steps, apply each strategy in turn to root traversal, then recursively to nested traversals.

Specified by:

applyStrategies in interface Traversal.Admin<S,E>

addStarts

public void addStarts(Iterator<Traverser.Admin<S>> starts)

Description copied from interface: Traversal.Admin

Add an iterator of Traverser.Admin objects to the head/start of the traversal. Users should typically not need to call this method. For dynamic inject of data, they should use InjectStep.

Specified by:

addStarts in interface Traversal.Admin<S,E>

Parameters:

starts - an iterators of traversers

addStart

public void addStart(Traverser.Admin<S> start)

Description copied from interface: Traversal.Admin

Add a single Traverser.Admin object to the head of the traversal. Users should typically not need to call this method. For dynamic inject of data, they should use InjectStep.

Specified by:

addStart in interface Traversal.Admin<S,E>

Parameters:

start - a traverser to add to the traversal

addStep

public <E2> Traversal.Admin<S,E2> addStep(Step<?,E2> step)

Description copied from interface: Traversal.Admin

Add a Step to the end of the traversal. This method should link the step to its next and previous step accordingly.

Specified by:

addStep in interface Traversal.Admin<S,E>

Type Parameters:

E2 - the output of the step

Parameters:

step - the step to add

Returns:

the updated traversal

getSteps

public List<Step> getSteps()

Description copied from interface: Traversal.Admin

Get the Step instances associated with this traversal. The steps are ordered according to their linked list structure as defined by Step.getPreviousStep() and Step.getNextStep().

Specified by:

getSteps in interface Traversal.Admin<S,E>

Returns:

the ordered steps of the traversal

clone

public EmptyTraversal<S,E> clone()

Description copied from interface: Traversal.Admin

Cloning is used to duplicate the traversal typically in OLAP environments.

Specified by:

clone in interface Traversal.Admin<S,E>

Overrides:

clone in class Object

Returns:

The cloned traversal

isLocked

public boolean isLocked()

Description copied from interface: Traversal.Admin

When the traversal has had its TraversalStrategies applied to it, it is locked.

Specified by:

isLocked in interface Traversal.Admin<S,E>

Returns:

whether the traversal is locked

lock

public void lock()

Description copied from interface: Traversal.Admin

Lock the traversal and perform any final adjustments to it after strategy application.

Specified by:

lock in interface Traversal.Admin<S,E>

getTraverserGenerator

public TraverserGenerator getTraverserGenerator()

Description copied from interface: Traversal.Admin

Get the TraverserGenerator associated with this traversal. The traversal generator creates Traverser instances that are respective of the traversal's TraverserRequirement.

Specified by:

getTraverserGenerator in interface Traversal.Admin<S,E>

Returns:

the generator of traversers

setSideEffects

public void setSideEffects(TraversalSideEffects sideEffects)

Description copied from interface: Traversal.Admin

Set the TraversalSideEffects of this traversal.

Specified by:

setSideEffects in interface Traversal.Admin<S,E>

Parameters:

sideEffects - the sideEffects to set for this traversal.

getStrategies

public TraversalStrategies getStrategies()

Description copied from interface: Traversal.Admin

Get the TraversalStrategies associated with this traversal.

Specified by:

getStrategies in interface Traversal.Admin<S,E>

Returns:

the strategies associated with this traversal

setParent

public void setParent(TraversalParent step)

Description copied from interface: Traversal.Admin

Set the TraversalParent Step that is the parent of this traversal. Traversals can be nested and this is the means by which the traversal tree is connected. If there is no parent, then it should be a EmptyStep.

Specified by:

setParent in interface Traversal.Admin<S,E>

Parameters:

step - the traversal holder parent step or EmptyStep if it has no parent

getParent

public TraversalParent getParent()

Description copied from interface: Traversal.Admin

Get the TraversalParent Step that is the parent of this traversal. Traversals can be nested and this is the means by which the traversal tree is walked.

Specified by:

getParent in interface Traversal.Admin<S,E>

Returns:

the traversal holder parent step or EmptyStep if it has no parent.

setStrategies

public void setStrategies(TraversalStrategies traversalStrategies)

Description copied from interface: Traversal.Admin

Set the TraversalStrategies to be used by this traversal at evaluation time.

Specified by:

setStrategies in interface Traversal.Admin<S,E>

Parameters:

traversalStrategies - the strategies to use on this traversal

addStep

public <S2,
E2> Traversal.Admin<S2,E2> addStep(int index,
 Step<?,?> step)
                                       throws IllegalStateException

Description copied from interface: Traversal.Admin

Add a Step to an arbitrary point in the traversal.

Specified by:

addStep in interface Traversal.Admin<S,E>

Type Parameters:

S2 - the new start type of the traversal (if the added step was a start step)

E2 - the new end type of the traversal (if the added step was an end step)

Parameters:

index - the location in the traversal to insert the step

step - the step to add

Returns:

the newly modulated traversal

Throws:

IllegalStateException - if the TraversalStrategies have already been applied

removeStep

public <S2,
E2> Traversal.Admin<S2,E2> removeStep(int index)
                                          throws IllegalStateException

Description copied from interface: Traversal.Admin

Remove a Step from the traversal. Those implementing this method should take care to reset state for the step in the GValueManager.

Specified by:

removeStep in interface Traversal.Admin<S,E>

Type Parameters:

S2 - the new start type of the traversal (if the removed step was a start step)

E2 - the new end type of the traversal (if the removed step was an end step)

Parameters:

index - the location in the traversal of the step to be evicted

Returns:

the newly modulated traversal

Throws:

IllegalStateException - if the TraversalStrategies have already been applied

equals

public boolean equals(Object object)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

getTraverserRequirements

public Set<TraverserRequirement> getTraverserRequirements()

Description copied from interface: Traversal.Admin

Get the set of all TraverserRequirements for this traversal.

Specified by:

getTraverserRequirements in interface Traversal.Admin<S,E>

Returns:

the features of a traverser that are required to execute properly in this traversal

getGraph

public Optional<Graph> getGraph()

Description copied from interface: Traversal.Admin

Gets the Graph instance associated directly to this Traversal or through its parent.

Specified by:

getGraph in interface Traversal.Admin<S,E>

setGraph

public void setGraph(Graph graph)

Specified by:

setGraph in interface Traversal.Admin<S,E>