Package com.hazelcast.jet
Interface Traverser<T>
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- Type Parameters:
T
- traversed item type
- All Known Implementing Classes:
AppendableTraverser
,ResettableSingletonTraverser
- Functional Interface:
- This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
@FunctionalInterface public interface Traverser<T>
Traverses a potentially infinite sequence of non-null
items. Each invocation ofnext()
consumes and returns the next item in the sequence if available, ornull
if not. If the traverser is null-terminated, getting anull
means it's exhausted and will keep returningnull
forever.All transformation methods (
map()
,append()
,peek()
, ...) are allowed to either return a new instance or to modifythis
instance. For correct functionality, you must always use the returned value and stop using the original instance.- Since:
- Jet 3.0
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Method Summary
All Methods Instance Methods Abstract Methods Default Methods Modifier and Type Method Description default Traverser<T>
append(T item)
Returns a traverser that will return all the items of this traverser, plus an additional item once this one returnsnull
.default Traverser<T>
dropWhile(java.util.function.Predicate<? super T> predicate)
Returns a traverser that will emit a suffix of the original traverser, starting from the item for which the predicate fails (inclusive).default Traverser<T>
filter(java.util.function.Predicate<? super T> filterFn)
Returns a traverser that will emit the same items as this traverser, but only those that pass the given predicate.default <R> Traverser<R>
flatMap(java.util.function.Function<? super T,? extends Traverser<R>> flatMapFn)
Returns a traverser that will apply the given mapping function to each item retrieved from this traverser and emit all the items from the resulting traversers, which must be null-terminated.default <R> Traverser<R>
map(java.util.function.Function<? super T,? extends R> mapFn)
Returns a traverser that will emit the results of applyingmapFn
to this traverser's items.T
next()
Returns the next item, removing it from this traverser.default Traverser<T>
onFirstNull(java.lang.Runnable action)
Returns a traverser that will emit the same items as this traverser and additionally run the supplied action the first time this traverser returnsnull
.default Traverser<T>
peek(java.util.function.Consumer<? super T> action)
Returns a traverser that will emit the same items as this traverser, additionally passing each (non-null) item to the supplied consumer.default Traverser<T>
prepend(T item)
Returns a traverser which prepends an additional item in front of all the items of this traverser.default Traverser<T>
takeWhile(java.util.function.Predicate<? super T> predicate)
Returns a traverser that will emit a prefix of the original traverser, up to the item for which the predicate fails (exclusive).
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Method Detail
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next
T next()
Returns the next item, removing it from this traverser. If no item is available, returnsnull
. If this traverser is null-terminated, getting anull
means it's exhausted and will keep returningnull
forever. Otherwise, trying again later may produce one.
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map
@Nonnull @CheckReturnValue default <R> Traverser<R> map(@Nonnull java.util.function.Function<? super T,? extends R> mapFn)
Returns a traverser that will emit the results of applyingmapFn
to this traverser's items. IfmapFn
returnsnull
for an item, the returned traverser drops it and immediately moves on to the next item from this traverser. This waymapFn
can perform filtering in addition to transformation.
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filter
@Nonnull @CheckReturnValue default Traverser<T> filter(@Nonnull java.util.function.Predicate<? super T> filterFn)
Returns a traverser that will emit the same items as this traverser, but only those that pass the given predicate.
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flatMap
@Nonnull @CheckReturnValue default <R> Traverser<R> flatMap(@Nonnull java.util.function.Function<? super T,? extends Traverser<R>> flatMapFn)
Returns a traverser that will apply the given mapping function to each item retrieved from this traverser and emit all the items from the resulting traversers, which must be null-terminated.The function must not return null traverser, but can return an empty traverser.
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takeWhile
@Nonnull @CheckReturnValue default Traverser<T> takeWhile(@Nonnull java.util.function.Predicate<? super T> predicate)
Returns a traverser that will emit a prefix of the original traverser, up to the item for which the predicate fails (exclusive).
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dropWhile
@Nonnull @CheckReturnValue default Traverser<T> dropWhile(@Nonnull java.util.function.Predicate<? super T> predicate)
Returns a traverser that will emit a suffix of the original traverser, starting from the item for which the predicate fails (inclusive).
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append
@Nonnull @CheckReturnValue default Traverser<T> append(@Nonnull T item)
Returns a traverser that will return all the items of this traverser, plus an additional item once this one returnsnull
. After that it continues forwarding the return values of this traverser. It is meant to be used on finite traversers.Default implementations always returns a new traverser instance. If you need to append multiple objects or use this method frequently,
AppendableTraverser
might be a better choice.
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prepend
@Nonnull @CheckReturnValue default Traverser<T> prepend(@Nonnull T item)
Returns a traverser which prepends an additional item in front of all the items of this traverser.
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peek
@Nonnull @CheckReturnValue default Traverser<T> peek(@Nonnull java.util.function.Consumer<? super T> action)
Returns a traverser that will emit the same items as this traverser, additionally passing each (non-null) item to the supplied consumer.
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