Traversal (Apache TinkerPop 3.4.13 API)

All Superinterfaces:

AutoCloseable, Cloneable, Iterator<E>, Serializable

All Known Subinterfaces:

GraphTraversal<S,E>, GraphTraversal.Admin<S,E>, Traversal.Admin<S,E>
```
public interface Traversal<S,E>
extends Iterator<E>, Serializable, Cloneable, AutoCloseable
```
A Traversal represents a directed walk over a Graph. This is the base interface for all traversal's, where each extending interface is seen as a domain specific language. For example, GraphTraversal is a domain specific language for traversing a graph using "graph concepts" (e.g. vertices, edges). Another example may represent the graph using "social concepts" (e.g. people, cities, artifacts). A Traversal is evaluated in one of two ways: iterator-based OLTP or GraphComputer-based OLAP. OLTP traversals leverage an iterator and are executed within a single JVM (with data access allowed to be remote). OLAP traversals leverage GraphComputer and are executed between multiple JVMs (and/or cores).

Author:

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

Nested Class Summary

Nested Classes
Modifier and Type	Interface and Description
`static interface`	`Traversal.Admin<S,E>`
`static class`	`Traversal.Exceptions` A collection of `Exception` types associated with Traversal execution.
`static class`	`Traversal.Symbols`

Method Summary

All Methods Instance Methods Default Methods
Modifier and Type	Method and Description
`default Traversal.Admin<S,E>`	`asAdmin()` Get access to administrative methods of the traversal via its accompanying `Traversal.Admin`.
`default void`	`close()` Releases resources opened in any steps that implement `AutoCloseable`.
`default org.apache.tinkerpop.gremlin.process.traversal.util.TraversalExplanation`	`explain()` Return a `TraversalExplanation` that shows how this traversal will mutate with each applied `TraversalStrategy`.
`default <C extends Collection<E>> C`	`fill(C collection)` Add all the results of the traversal to the provided collection.
`default <E2> void`	`forEachRemaining(Class<E2> endType, Consumer<E2> consumer)` A traversal can be rewritten such that its defined end type E may yield objects of a different type.
`default void`	`forEachRemaining(Consumer<? super E> action)`
`default <A,B> Traversal<A,B>`	`iterate()` Iterate all the `Traverser` instances in the traversal.
`default List<E>`	`next(int amount)` Get the next n-number of results from the traversal.
`default Traversal<S,E>`	`none()` Filter all traversers in the traversal.
`default void`	`notifyClose()` Gets a callback from `close()` for additional operations specific to the `Traversal` implementation.
`default Traversal<S,org.apache.tinkerpop.gremlin.process.traversal.util.TraversalMetrics>`	`profile()` Profile the traversal.
`default <T> CompletableFuture<T>`	`promise(Function<Traversal<S,E>,T> traversalFunction)` Starts a promise to execute a function on the current `Traversal` that will be completed in the future.
`default org.apache.tinkerpop.gremlin.process.traversal.step.util.BulkSet<E>`	`toBulkSet()` Put all the results into a `BulkSet`.
`default List<E>`	`toList()` Put all the results into an `ArrayList`.
`default Set<E>`	`toSet()` Put all the results into a `HashSet`.
`default Stream<E>`	`toStream()` Return the traversal as a `Stream`.
`default Optional<E>`	`tryNext()` Return an `Optional` of the next E object in the traversal.

Methods inherited from interface java.util.Iterator
hasNext, next, remove

- Method Detail
  - asAdmin
```
default Traversal.Admin<S,E> asAdmin()
```
    Get access to administrative methods of the traversal via its accompanying Traversal.Admin.
    
    Returns:
    
    the admin of this traversal
  - tryNext
```
default Optional<E> tryNext()
```
    Return an Optional of the next E object in the traversal. If the traversal is empty, then an Optional.empty() is returned.
    
    Returns:
    
    an optional of the next object in the traversal
  - next
```
default List<E> next(int amount)
```
    Get the next n-number of results from the traversal. If the traversal has less than n-results, then only that number of results are returned.
    
    Parameters:
    
    amount - the number of results to get
    
    Returns:
    
    the n-results in a List
  - toList
```
default List<E> toList()
```
    Put all the results into an ArrayList.
    
    Returns:
    
    the results in a list
  - toSet
```
default Set<E> toSet()
```
    Put all the results into a HashSet.
    
    Returns:
    
    the results in a set
  - toBulkSet
```
default org.apache.tinkerpop.gremlin.process.traversal.step.util.BulkSet<E> toBulkSet()
```
    Put all the results into a BulkSet. This can reduce both time and space when aggregating results by ensuring a weighted set.
    
    Returns:
    
    the results in a bulk set
  - toStream
```
default Stream<E> toStream()
```
    Return the traversal as a Stream.
    
    Returns:
    
    the traversal as a stream.
  - promise
```
default <T> CompletableFuture<T> promise(Function<Traversal<S,E>,T> traversalFunction)
```
    Starts a promise to execute a function on the current Traversal that will be completed in the future. Note that this method can only be used if the Traversal is constructed using TraversalSource.withRemote(Configuration). Calling this method otherwise will yield an IllegalStateException.
  - fill
```
default <C extends Collection<E>> C fill(C collection)
```
    Add all the results of the traversal to the provided collection.
    
    Parameters:
    
    collection - the collection to fill
    
    Returns:
    
    the collection now filled
  - iterate
```
default <A,B> Traversal<A,B> iterate()
```
    Iterate all the Traverser instances in the traversal. What is returned is the empty traversal. It is assumed that what is desired from the computation is are the sideEffects yielded by the traversal.
    
    Returns:
    
    the fully drained traversal
  - none
```
default Traversal<S,E> none()
```
    Filter all traversers in the traversal. This step has narrow use cases and is primarily intended for use as a signal to remote servers that iterate() was called. While it may be directly used, it is often a sign that a traversal should be re-written in another form.
    
    Returns:
    
    the updated traversal with respective NoneStep.
  - profile
```
default Traversal<S,org.apache.tinkerpop.gremlin.process.traversal.util.TraversalMetrics> profile()
```
    Profile the traversal.
    
    Returns:
    
    the updated traversal with respective ProfileSideEffectStep.
  - explain
```
default org.apache.tinkerpop.gremlin.process.traversal.util.TraversalExplanation explain()
```
    Return a TraversalExplanation that shows how this traversal will mutate with each applied TraversalStrategy.
    
    Returns:
    
    a traversal explanation
  - forEachRemaining
```
default <E2> void forEachRemaining(Class<E2> endType,
                                   Consumer<E2> consumer)
```
    A traversal can be rewritten such that its defined end type E may yield objects of a different type. This helper method allows for the casting of the output to the known the type.
    
    Type Parameters:
    
    E2 - the known output type of the traversal
    
    Parameters:
    
    endType - the true output type of the traversal
    
    consumer - a Consumer to process each output
  - forEachRemaining
```
default void forEachRemaining(Consumer<? super E> action)
```
    Specified by:
    
    forEachRemaining in interface Iterator<E>
  - close
```
default void close()
            throws Exception
```
    Releases resources opened in any steps that implement AutoCloseable. If this method is overridden,the implementer should invoke notifyClose().
    
    Specified by:
    
    close in interface AutoCloseable
    
    Throws:
    
    Exception
  - notifyClose
```
default void notifyClose()
```
    Gets a callback from close() for additional operations specific to the Traversal implementation. A good implementation will use close() to release resources in steps and this method to release resources specific to the Traversal implementations.

Interface Traversal<S,E>

Nested Class Summary

Method Summary

Methods inherited from interface java.util.Iterator

Method Detail

asAdmin

tryNext

next

toList

toSet

toBulkSet

toStream

promise

fill

iterate

none

profile

explain

forEachRemaining

forEachRemaining

close

notifyClose