org.calrissian.mango.collect

Class CloseableIterators

java.lang.Object

org.calrissian.mango.collect.CloseableIterators

public class CloseableIterators
extends Object

Utility class to develop commonly used closeable iterator functions.

Method Summary

Methods

Modifier and Type	Method and Description
static <T> int	advance(CloseableIterator<T> iterator, int numberToAdvance) Calls next() on iterator, either numberToAdvance times or until hasNext() returns false, whichever comes first.
static <T> CloseableIterator<T>	chain(CloseableIterator<? extends T>... iterators) Combines multiple closeable iterators into a single closeable iterator.
static <T> CloseableIterator<T>	chain(Iterator<? extends CloseableIterator<? extends T>> iterator) Combines multiple closeable iterators into a single closeable iterator.
static <T> CloseableIterator<T>	concat(CloseableIterator<? extends Iterator<? extends T>> iterators) Combines multiple iterators into a single closeable iterator.
static <T> CloseableIterator<T>	distinct(CloseableIterator<T> iterator) If we can assume the closeable iterator is sorted, return the distinct elements.
static <T> CloseableIterator<T>	emptyIterator() Returns an empty closeable iterator.
static <T> CloseableIterator<T>	filter(CloseableIterator<T> iterator, Predicate<T> filter) Returns the elements of unfiltered that satisfy a predicate.
static <T> CloseableIterator<T>	limit(CloseableIterator<T> iterator, int limitSize) Creates a closeable iterator returning the first limitSize elements of the given closeable iterator.
static <T> PeekingCloseableIterator<T>	peekingIterator(CloseableIterator<T> iterator) /** Returns a PeekingCloseableIterator backed by the given closeable iterator.
static <F,T> CloseableIterator<T>	transform(CloseableIterator<F> iterator, Function<F,T> function) Returns a closeable iterator that applies function to each element of fromIterator.
static <T> CloseableIterator<T>	wrap(Iterator<T> iterator) Creates a CloseableIterator from a standard iterator.

Methods inherited from class java.lang.Object

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

Method Detail

transform

public static <F,T> CloseableIterator<T> transform(CloseableIterator<F> iterator,
                                   Function<F,T> function)

Returns a closeable iterator that applies function to each element of fromIterator.

peekingIterator

public static <T> PeekingCloseableIterator<T> peekingIterator(CloseableIterator<T> iterator)

/** Returns a PeekingCloseableIterator backed by the given closeable iterator. Calls to peek do not change the state of the iterator. The subsequent call to next after peeking will always return the same value.

limit

public static <T> CloseableIterator<T> limit(CloseableIterator<T> iterator,
                             int limitSize)

Creates a closeable iterator returning the first limitSize elements of the given closeable iterator. If the original closeable iterator does not contain that many elements, the returned closeable iterator will have the same behavior as the original.

filter

public static <T> CloseableIterator<T> filter(CloseableIterator<T> iterator,
                              Predicate<T> filter)

Returns the elements of unfiltered that satisfy a predicate.

advance

public static <T> int advance(CloseableIterator<T> iterator,
              int numberToAdvance)

Calls next() on iterator, either numberToAdvance times or until hasNext() returns false, whichever comes first.

emptyIterator

public static <T> CloseableIterator<T> emptyIterator()

Returns an empty closeable iterator.

concat

public static <T> CloseableIterator<T> concat(CloseableIterator<? extends Iterator<? extends T>> iterators)

Combines multiple iterators into a single closeable iterator. The returned closeable iterator iterates across the elements of each iterator in inputs. The input iterators are not polled until necessary.

Type Parameters:

T -

Parameters:

iterators -

Returns:

chain

public static <T> CloseableIterator<T> chain(CloseableIterator<? extends T>... iterators)

Combines multiple closeable iterators into a single closeable iterator. The returned closeable iterator iterates across the elements of each closeable iterator in inputs. The input iterators are not polled until necessary. As each closeable iterator is exhausted, it is closed before moving onto the next closeable iterator. A call to close on the returned closeable iterator will quietly close all of the closeable iterators in inputs which have not been exhausted.

chain

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

Combines multiple closeable iterators into a single closeable iterator. The returned closeable iterator iterates across the elements of each closeable iterator in inputs. The input iterators are not polled until necessary. As each closeable iterator is exhausted, it is closed before moving onto the next closeable iterator. A call to close on the returned closeable iterator will quietly close all of the closeable iterators in inputs which have not been exhausted.

distinct

public static <T> CloseableIterator<T> distinct(CloseableIterator<T> iterator)

If we can assume the closeable iterator is sorted, return the distinct elements. This only works if the data provided is sorted.

wrap

public static <T> CloseableIterator<T> wrap(Iterator<T> iterator)

Creates a CloseableIterator from a standard iterator.