de.unkrig.commons.util.collections

Class IteratorUtil

java.lang.Object

de.unkrig.commons.util.collections.IteratorUtil

public final class IteratorUtil
extends Object

Various Iterator-related utility methods.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	IteratorUtil.ArrayIterator<T> An Iterator that has a notion of an "array index", which is the index of the "next" element in an array.

Field Summary

Fields

Modifier and Type	Field and Description
static Iterator	AT_END An iterator which is at its end.

Method Summary

Modifier and Type	Method and Description
static <T> void	addAllElementsTo(Iterator<? extends T> iterator, Collection<? super T> target) Adds all remaining products of the iterator to the target collection.
static <T> Iterator<T>	atEnd()
static int	elementCount(Iterator<Integer> iterator) Retrieves, counts and discards all elements remaining on the iterator
static <T> Iterator<T>	filter(Iterator<? extends T> delegate, PredicateWhichThrows<? super T,? extends RuntimeException> qualifies) Returns an iterator which skips the elements of the delegate which do not qualifiy.
static Iterator<Integer>	foR(int start, int end) Equivalent with foR(start, end,1).
static Iterator<Integer>	foR(int start, int end, int step) Creates and returns an Iterator<Integer> that counts from start (inclusively) to end (exclusively), with a step increment.
static <T> IteratorUtil.ArrayIterator<T>	iterator(T[] array)
static <T> Iterator<ElementWithContext<T>>	iteratorWithContext(Iterator<? extends T> delegate) Wraps the delegate iterator in an Iterator<ElementWithContext>.
static <T> Iterator<T>	repeat(int n, T value)
static <T> Iterator<T>	repeat(T value)
static <E> ListIterator<E>	reverse(ListIterator<E> delegate) Returns a list iterator that traverses the list elements in the reverse order of the given delegate.
static <I,O> Iterator<O>	transform(Iterator<? extends I> delegate, Transformer<? super I,? extends O> transform) Returns an iterator which iterates the transformed elements of the delegate

Methods inherited from class java.lang.Object

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

Field Detail

AT_END

public static final Iterator AT_END

An iterator which is at its end.

To get the non-rawe type, use atEnd().

Method Detail

atEnd

public static <T> Iterator<T> atEnd()

Returns:

An Iterator which is always at its end

filter

public static <T> Iterator<T> filter(Iterator<? extends T> delegate,
                                     PredicateWhichThrows<? super T,? extends RuntimeException> qualifies)

Returns an iterator which skips the elements of the delegate which do not qualifiy.

transform

public static <I,O> Iterator<O> transform(Iterator<? extends I> delegate,
                                          Transformer<? super I,? extends O> transform)

Returns an iterator which iterates the transformed elements of the delegate

repeat

public static <T> Iterator<T> repeat(T value)

Returns:

An iterator that produces an infinite sequence of value elements

reverse

public static <E> ListIterator<E> reverse(ListIterator<E> delegate)

Returns a list iterator that traverses the list elements in the reverse order of the given delegate.

Notice that iff !delegate.hasPrevious(), then !reverse(delegate).hasNext(). In other words, you will often use

 IteratorUtil.reverse(list.listIterator(list.size()))

, and not simply

 IteratorUtil.reverse(list.listIterator())

repeat

public static <T> Iterator<T> repeat(int n,
                                     T value)

Returns:

An iterator that produces a sequence of n value elements

iterator

public static <T> IteratorUtil.ArrayIterator<T> iterator(T[] array)

Returns:

An iterator over the elements of the array

elementCount

public static int elementCount(Iterator<Integer> iterator)

Retrieves, counts and discards all elements remaining on the iterator

iteratorWithContext

public static <T> Iterator<ElementWithContext<T>> iteratorWithContext(Iterator<? extends T> delegate)

Wraps the delegate iterator in an Iterator<ElementWithContext>.

Parameters:

delegate - Must produce non-null values

Returns:

An iterator that produces ElementWithContexts from the sequence produced by the delegate

foR

public static Iterator<Integer> foR(int start,
                                    int end)

Equivalent with foR(start, end,1).

See Also:

foR(int, int, int)

foR

public static Iterator<Integer> foR(int start,
                                    int end,
                                    int step)

Creates and returns an Iterator<Integer> that counts from start (inclusively) to end (exclusively), with a step increment.

More precise: Iff step is greater than zero, then the returned iterator produces the values start, start + step, and so forth, and ends with the last value which is less than end.

Otherwise, iff step is less than zero, then the returned iterator produces the values start, start + step, and so forth, and ends with the last value which is greater than end.

Otherwise, step is zero, and the returned iterator produces either an infinite sequence of values start, or, iff start == end, an empty sequence.

Throws:

IllegalArgumentException - step > 0 && end < start

IllegalArgumentException - step < 0 && end > start

addAllElementsTo

public static <T> void addAllElementsTo(Iterator<? extends T> iterator,
                                        Collection<? super T> target)

Adds all remaining products of the iterator to the target collection.