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

Class EmptyStep<S,E>

java.lang.Object

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

All Implemented Interfaces:

Serializable, AutoCloseable, Cloneable, Iterator<Traverser.Admin<E>>, Step<S,E>, TraversalParent

public final class EmptyStep<S,E>
extends Object
implements Step<S,E>, TraversalParent

Author:

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

See Also:

Serialized Form

Method Summary

Modifier and Type	Method	Description
void	addLabel(String label)	Add a label to this step.
void	addStart(Traverser.Admin<S> start)	Add a single Traverser.Admin to the step.
void	addStarts(Iterator<Traverser.Admin<S>> starts)	Add an iterator of Traverser.Admin objects of type S to the step.
void	clearLabels()	Removes all labels on the step.
EmptyStep<S,E>	clone()	Cloning is used to duplicate steps for the purpose of traversal optimization and OLTP replication.
boolean	equals(Object object)
String	getId()	Get the unique id of this step.
Set<String>	getLabels()	Get the labels of this step.
Step<E,?>	getNextStep()	Get the next step to the current step.
Step<?,S>	getPreviousStep()	Get the step prior to the current step.
Set<TraverserRequirement>	getRequirements()	Provide the necessary TraverserRequirement that must be met by the traverser in order for the step to function properly.
<A,B> Traversal.Admin<A,B>	getTraversal()	Get the Traversal.Admin that this step is contained within.
int	hashCode()
boolean	hasNext()
boolean	hasStarts()	Determines if starts objects are present without iterating forward.
static <S,E> EmptyStep<S,E>	instance()
Traverser.Admin<E>	next()
void	removeLabel(String label)	Remove a label from this step.
void	reset()	Reset the state of the step such that it has no incoming starts.
void	setId(String id)	Get the unique id of the step.
void	setNextStep(Step<E,?> step)	Set the step that is next to the current step.
void	setPreviousStep(Step<?,S> step)	Set the step that is previous to the current step.
void	setTraversal(Traversal.Admin<?,?> traversal)	Set the Traversal that this step is contained within.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Iterator

forEachRemaining, remove

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

equals

Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent

addGlobalChild, addLocalChild, asStep, close, getGlobalChildren, getLocalChildren, getSelfAndChildRequirements, integrateChild, removeGlobalChild, removeLocalChild, replaceLocalChild

Method Detail

instance

public static <S,E> EmptyStep<S,E> instance()

addStarts

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

Description copied from interface: Step

Add an iterator of Traverser.Admin objects of type S to the step.

Specified by:

addStarts in interface Step<S,E>

Parameters:

starts - The iterator of objects to add

hasStarts

public boolean hasStarts()

Description copied from interface: Step

Determines if starts objects are present without iterating forward. This function has special applicability around ReducingBarrierStep implementations where they always return true for calls to Iterator.hasNext(). Using this function gives insight to what the step itself is holding in its iterator without performing any sort of processing on the step itself.

Specified by:

hasStarts in interface Step<S,E>

addStart

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

Description copied from interface: Step

Add a single Traverser.Admin to the step.

Specified by:

addStart in interface Step<S,E>

Parameters:

start - The traverser to add

setPreviousStep

public void setPreviousStep(Step<?,S> step)

Description copied from interface: Step

Set the step that is previous to the current step. Used for linking steps together to form a function chain.

Specified by:

setPreviousStep in interface Step<S,E>

Parameters:

step - the previous step of this step

reset

public void reset()

Description copied from interface: Step

Reset the state of the step such that it has no incoming starts. Internal states are to be reset, but any sideEffect data structures are not to be recreated.

Specified by:

reset in interface Step<S,E>

getPreviousStep

public Step<?,S> getPreviousStep()

Description copied from interface: Step

Get the step prior to the current step.

Specified by:

getPreviousStep in interface Step<S,E>

Returns:

The previous step

setNextStep

public void setNextStep(Step<E,?> step)

Description copied from interface: Step

Set the step that is next to the current step. Used for linking steps together to form a function chain.

Specified by:

setNextStep in interface Step<S,E>

Parameters:

step - the next step of this step

getNextStep

public Step<E,?> getNextStep()

Description copied from interface: Step

Get the next step to the current step.

Specified by:

getNextStep in interface Step<S,E>

Returns:

The next step

getTraversal

public <A,B> Traversal.Admin<A,B> getTraversal()

Description copied from interface: Step

Get the Traversal.Admin that this step is contained within.

Specified by:

getTraversal in interface Step<S,E>

Type Parameters:

A - The incoming object type of the traversal

B - The outgoing object type of the traversal

Returns:

The traversal of this step

setTraversal

public void setTraversal(Traversal.Admin<?,?> traversal)

Description copied from interface: Step

Set the Traversal that this step is contained within.

Specified by:

setTraversal in interface Step<S,E>

Parameters:

traversal - the new traversal for this step

clone

public EmptyStep<S,E> clone()

Description copied from interface: Step

Cloning is used to duplicate steps for the purpose of traversal optimization and OLTP replication. When cloning a step, it is important that the steps, the cloned step is equivalent to the state of the step when Step.reset() is called. Moreover, the previous and next steps should be set to EmptyStep.

Specified by:

clone in interface Step<S,E>

Overrides:

clone in class Object

Returns:

The cloned step

getLabels

public Set<String> getLabels()

Description copied from interface: Step

Get the labels of this step. The labels are ordered by the order of the calls to Step.addLabel(java.lang.String).

Specified by:

getLabels in interface Step<S,E>

Returns:

the set of labels for this step

addLabel

public void addLabel(String label)

Description copied from interface: Step

Add a label to this step.

Specified by:

addLabel in interface Step<S,E>

Parameters:

label - the label to add to this step

removeLabel

public void removeLabel(String label)

Description copied from interface: Step

Remove a label from this step.

Specified by:

removeLabel in interface Step<S,E>

Parameters:

label - the label to remove from this step

clearLabels

public void clearLabels()

Description copied from interface: Step

Removes all labels on the step.

Specified by:

clearLabels in interface Step<S,E>

setId

public void setId(String id)

Description copied from interface: Step

Get the unique id of the step. These ids can change when strategies are applied and anonymous traversals are embedded in the parent traversal. A developer should typically not need to call this method.

Specified by:

setId in interface Step<S,E>

Parameters:

id - the unique id of the step

getId

public String getId()

Description copied from interface: Step

Get the unique id of this step.

Specified by:

getId in interface Step<S,E>

Returns:

the unique id of the step

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<S>

next

public Traverser.Admin<E> next()

Specified by:

next in interface Iterator<S>

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object object)

Overrides:

equals in class Object

getRequirements

public Set<TraverserRequirement> getRequirements()

Description copied from interface: Step

Provide the necessary TraverserRequirement that must be met by the traverser in order for the step to function properly. The provided default implements returns an empty set.

Specified by:

getRequirements in interface Step<S,E>

Returns:

the set of requirements