com.hazelcast.jet

Class Traversers

java.lang.Object

com.hazelcast.jet.Traversers

public final class Traversers
extends Object

Utility class with several Traversers useful in Processor implementations.

Since:

Jet 3.0

Method Summary

Modifier and Type	Method and Description
static <T> Traverser<T>	empty() Returns a traverser that always returns null.
static <T> Traverser<T>	lazy(Supplier<Traverser<T>> supplierOfTraverser) Flattens a supplier of traverser into a lazy-initialized traverser.
static <T> Traverser<T>	singleton(T item) Returns a traverser over the given single item.
static <T> Traverser<T>	traverseArray(T[] array) Returns a traverser over the given array.
static <T> Traverser<T>	traverseEnumeration(Enumeration<T> enumeration) Returns an adapter from Enumeration to Traverser.
static <T> Traverser<T>	traverseItems(T... items) Returns a traverser over the supplied arguments (or item array).
static <T> Traverser<T>	traverseIterable(Iterable<? extends T> iterable) Returns a traverser over the given iterable.
static <T> Traverser<T>	traverseIterator(Iterator<? extends T> iterator) Returns an adapter from Iterator to Traverser.
static <T> Traverser<T>	traverseIterator(Iterator<? extends T> iterator, boolean ignoreNulls) Returns an adapter from Iterator to Traverser.
static <T> Traverser<T>	traverseSpliterator(Spliterator<T> spliterator) Returns an adapter from Spliterator to Traverser.
static <T> Traverser<T>	traverseStream(Stream<T> stream) Returns a traverser over the given stream.

Methods inherited from class java.lang.Object

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

Method Detail

empty

@Nonnull
public static <T> Traverser<T> empty()

Returns a traverser that always returns null.

singleton

@Nonnull
public static <T> Traverser<T> singleton(@Nonnull
                                                  T item)

Returns a traverser over the given single item.

You can use ResettableSingletonTraverser for less GC litter, if you can reuse the traverser instance.

traverseIterator

@Nonnull
public static <T> Traverser<T> traverseIterator(@Nonnull
                                                         Iterator<? extends T> iterator)

Returns an adapter from Iterator to Traverser. The iterator must return non-null items. Each time its next() method is called, the traverser will take another item from the iterator and return it.

traverseIterator

@Nonnull
public static <T> Traverser<T> traverseIterator(@Nonnull
                                                         Iterator<? extends T> iterator,
                                                         boolean ignoreNulls)

Returns an adapter from Iterator to Traverser. Each time its next() method is called, the traverser will take another item from the iterator and return it.

Parameters:

ignoreNulls - if true, null elements form the iterator will be filtered out. If false, error will be thrown on null elements.

traverseSpliterator

@Nonnull
public static <T> Traverser<T> traverseSpliterator(@Nonnull
                                                            Spliterator<T> spliterator)

Returns an adapter from Spliterator to Traverser. Each time its next() method is called, the traverser calls Spliterator.tryAdvance(Consumer). If it returns true, the traverser returns the item it emitted to the consumer; otherwise the traverser returns null. The spliterator must not emit null items.

traverseEnumeration

@Nonnull
public static <T> Traverser<T> traverseEnumeration(@Nonnull
                                                            Enumeration<T> enumeration)

Returns an adapter from Enumeration to Traverser. Each time its next() method is called, the traverser takes another item from the enumeration and returns it. The enumeration must not contain null items.

traverseStream

@Nonnull
public static <T> Traverser<T> traverseStream(@Nonnull
                                                       Stream<T> stream)

Returns a traverser over the given stream. It will traverse it through its spliterator, which it obtains immediately. When it exhausts the stream, it closes it. The stream must not contain null items.

traverseIterable

@Nonnull
public static <T> Traverser<T> traverseIterable(@Nonnull
                                                         Iterable<? extends T> iterable)

Returns a traverser over the given iterable. It obtains the iterator immediately.

traverseArray

@Nonnull
public static <T> Traverser<T> traverseArray(@Nonnull
                                                      T[] array)

Returns a traverser over the given array. Null elements in the array are skipped.

traverseItems

@SafeVarargs
public static <T> Traverser<T> traverseItems(T... items)

Returns a traverser over the supplied arguments (or item array). Null items are skipped.

Type Parameters:

T - type of the items

Parameters:

items - the items to traverse over

lazy

@Nonnull
public static <T> Traverser<T> lazy(@Nonnull
                                             Supplier<Traverser<T>> supplierOfTraverser)

Flattens a supplier of traverser into a lazy-initialized traverser. It obtains the traverser from this method's argument just once, upon the first invocation of get().