alluxio.resource

Class CloseableIterator<T>

java.lang.Object

alluxio.resource.CloseableResource<Iterator<T>>

alluxio.resource.CloseableIterator<T>

Type Parameters:

T - the type of elements returned by the iterator

All Implemented Interfaces:

Closeable, AutoCloseable, Iterator<T>

public abstract class CloseableIterator<T>
extends CloseableResource<Iterator<T>>
implements Iterator<T>

A CloseableIterator<T> is an iterator which requires cleanup when it is no longer in use. When the user creates CloseableIterator, the closeResource() method needs to be implemented to define how the resource can be closed. The iterator is not necessarily Closeable so we do not provide a default implementation for closeResource(). Users are required to use the factory methods instead of the constructors to create instances.

Method Summary

Modifier and Type	Method and Description
static <T> CloseableIterator<T>	concat(CloseableIterator<T> a, CloseableIterator<T> b) Combines two iterators into a single iterator.
static <T> CloseableIterator<T>	concat(List<CloseableIterator<T>> iterators) Concatenates iterators.
static <T> CloseableIterator<T>	create(Iterator<? extends T> iterator, java.util.function.Consumer<Void> closeAction) Wrap around an iterator with a resource to close.
boolean	hasNext()
T	next()
static <T> CloseableIterator<T>	noopCloseable(Iterator<? extends T> iterator) Wraps around an iterator with no resource to close.
static int	size(CloseableIterator<?> iter) Consumes the iterator, closes it, and returns its size.

Methods inherited from class alluxio.resource.CloseableResource

close, closeResource, get

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Iterator

forEachRemaining, remove

Method Detail

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<T>

next

public T next()

Specified by:

next in interface Iterator<T>

create

public static <T> CloseableIterator<T> create(Iterator<? extends T> iterator,
                                              java.util.function.Consumer<Void> closeAction)

Wrap around an iterator with a resource to close. How to close the resource is defined by the caller in the lambda expression.

Type Parameters:

T - the type of the iterable

Parameters:

iterator - the iterator to wrap around

closeAction - the callback to properly clean up the resource

Returns:

the closeable iterator

noopCloseable

public static <T> CloseableIterator<T> noopCloseable(Iterator<? extends T> iterator)

Wraps around an iterator with no resource to close.

Type Parameters:

T - the type of the iterable

Parameters:

iterator - the iterator to wrap around

Returns:

the closeable iterator

concat

public static <T> CloseableIterator<T> concat(CloseableIterator<T> a,
                                              CloseableIterator<T> b)

Combines two iterators into a single iterator.

Type Parameters:

T - type of iterator

Parameters:

a - an iterator

b - another iterator

Returns:

the concatenated iterator

concat

public static <T> CloseableIterator<T> concat(List<CloseableIterator<T>> iterators)

Concatenates iterators.

Type Parameters:

T - type of iterator

Parameters:

iterators - a list of iterators

Returns:

a concatenated iterator that iterate over all elements from each of the child iterators

size

public static int size(CloseableIterator<?> iter)

Consumes the iterator, closes it, and returns its size.

Parameters:

iter - the iter to get the size of

Returns:

the size of the iter