Class IteratorExtensions
- java.lang.Object
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- org.eclipse.xtext.xbase.lib.IteratorExtensions
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@GwtCompatible public class IteratorExtensions extends java.lang.Object
This is an extension library foriterators
.
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Constructor Summary
Constructors Constructor Description IteratorExtensions()
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static boolean
contains(java.util.Iterator<?> iterator, java.lang.Object o)
Returns true if this Iterator contains the specified element.static <T> java.util.Iterator<T>
drop(java.util.Iterator<T> iterator, int count)
Returns a view on this iterator that provides all elements except the firstcount
entries.static <T> java.util.Iterator<T>
dropWhile(java.util.Iterator<? extends T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returns an Iterator containing all elements starting from the first element for which the drop-predicate returned false.static boolean
elementsEqual(java.util.Iterator<?> iterator, java.lang.Iterable<?> iterable)
Determines whether two iterators contain equal elements in the same order.static boolean
elementsEqual(java.util.Iterator<?> iterator, java.util.Iterator<?> other)
Determines whether two iterators contain equal elements in the same order.static <T> boolean
exists(java.util.Iterator<T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returnstrue
if one or more elements initerator
satisfy the predicate.static <T> java.util.Iterator<T>
filter(java.util.Iterator<?> unfiltered, java.lang.Class<T> type)
Returns all instances of classtype
inunfiltered
.static <T> java.util.Iterator<T>
filter(java.util.Iterator<T> unfiltered, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returns the elements ofunfiltered
that satisfy a predicate.static <T> java.util.Iterator<T>
filterNull(java.util.Iterator<T> unfiltered)
Returns a new iterator filtering any null references.static <T> T
findFirst(java.util.Iterator<T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Finds the first element in the given iterator that fulfills the predicate.static <T> T
findLast(java.util.Iterator<T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Finds the last element in the given iterator that fulfills the predicate.static <T,R>
java.util.Iterator<R>flatMap(java.util.Iterator<T> original, Functions.Function1<? super T,? extends java.util.Iterator<R>> transformation)
Returns an iterable that performs the giventransformation
for each element oforiginal
when requested.static <T> java.util.Iterator<T>
flatten(java.util.Iterator<? extends java.util.Iterator<? extends T>> inputs)
Combines multiple iterators into a single iterator.static <T,R>
Rfold(java.util.Iterator<T> iterator, R seed, Functions.Function2<? super R,? super T,? extends R> function)
Applies the combinatorfunction
to all elements of the iterator in turn and usesseed
as the start value.static <T> boolean
forall(java.util.Iterator<T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returnstrue
if every element initerator
satisfies the predicate.static <T> void
forEach(java.util.Iterator<T> iterator, Procedures.Procedure1<? super T> procedure)
Appliesprocedure
for each element of the given iterator.static <T> void
forEach(java.util.Iterator<T> iterator, Procedures.Procedure2<? super T,? super java.lang.Integer> procedure)
Appliesprocedure
for each element of the given iterator.static <K,V>
java.util.Map<K,java.util.List<V>>groupBy(java.util.Iterator<? extends V> values, Functions.Function1<? super V,? extends K> computeKeys)
Returns a map for which theMap.values()
is a collection of lists, where the elements in the list will appear in the order as they appeared in the iterator.static <T> T
head(java.util.Iterator<T> iterator)
Returns the first element in the given iterator ornull
if empty.static <A> java.util.Iterator<Pair<java.lang.Integer,A>>
indexed(java.util.Iterator<? extends A> iterator)
Returns an Iterator of Pairs where the nth pair is created by taking the nth element of the source as the value and its 0-based index as the key.static boolean
isEmpty(java.util.Iterator<?> iterator)
Determines if the given iterator contains no elements.static boolean
isNullOrEmpty(java.util.Iterator<?> iterator)
Determines if the given iterator isnull
or contains no elements.static java.lang.String
join(java.util.Iterator<?> iterator)
Returns the concatenated string representation of the elements in the given iterator.static java.lang.String
join(java.util.Iterator<?> iterator, java.lang.CharSequence separator)
Returns the concatenated string representation of the elements in the given iterator.static <T> java.lang.String
join(java.util.Iterator<T> iterator, java.lang.CharSequence before, java.lang.CharSequence separator, java.lang.CharSequence after, Functions.Function1<? super T,? extends java.lang.CharSequence> function)
Returns the concatenated string representation of the elements in the given iterator.static <T> java.lang.String
join(java.util.Iterator<T> iterator, java.lang.CharSequence separator, Functions.Function1<? super T,? extends java.lang.CharSequence> function)
Returns the concatenated string representation of the elements in the given iterator.static <T> T
last(java.util.Iterator<T> iterator)
Returns the last element in the given iterator ornull
if empty.static <T,R>
java.util.Iterator<R>map(java.util.Iterator<T> original, Functions.Function1<? super T,? extends R> transformation)
Returns an iterator that performs the giventransformation
for each element oforiginal
when requested.static <T extends java.lang.Comparable<? super T>>
Tmax(java.util.Iterator<T> iterator)
Finds the maximum of the elements according to their natural ordering.static <T> T
max(java.util.Iterator<T> iterator, java.util.Comparator<? super T> comparator)
Finds the maximum element according tocomparator
.static <T,C extends java.lang.Comparable<? super C>>
TmaxBy(java.util.Iterator<T> iterator, Functions.Function1<? super T,C> compareBy)
Finds the element that yields the maximum value when passed tocompareBy
If there are several maxima, the first one will be returned.static <T extends java.lang.Comparable<? super T>>
Tmin(java.util.Iterator<T> iterator)
Finds the minimum of the given elements according to their natural ordering.static <T> T
min(java.util.Iterator<T> iterator, java.util.Comparator<? super T> comparator)
Finds the mininmum element according tocomparator
.static <T,C extends java.lang.Comparable<? super C>>
TminBy(java.util.Iterator<T> iterator, Functions.Function1<? super T,C> compareBy)
Finds the element that yields the minimum value when passed tocompareBy
.static <T> java.util.Iterator<T>
operator_plus(java.util.Iterator<? extends T> a, java.util.Iterator<? extends T> b)
Concatenates two iterators into a single iterator.static <T> T
reduce(java.util.Iterator<? extends T> iterator, Functions.Function2<? super T,? super T,? extends T> function)
Applies the combinatorfunction
to all elements of the iterator in turn.static <T> java.util.Iterator<T>
reject(java.util.Iterator<T> unfiltered, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returns the elements ofunfiltered
that do not satisfy a predicate.static int
size(java.util.Iterator<?> iterator)
Returns the number of elements initerator
.static <T> java.util.Iterator<T>
tail(java.util.Iterator<T> iterator)
Returns a view on this iterator that contains all the elements except the first.static <T> java.util.Iterator<T>
take(java.util.Iterator<T> iterator, int count)
Returns a view on this iterator that provides at most the firstcount
entries.static <T> java.util.Iterator<T>
takeWhile(java.util.Iterator<? extends T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returns an Iterator containing all elements starting from the head of the source up to and excluding the first element that violates the predicate.static <K,V>
java.util.Map<K,V>toInvertedMap(java.util.Iterator<? extends K> keys, Functions.Function1<? super K,V> computeValues)
Returns a map for which theMap.values()
are computed by the given function, and each key is an element in the givenkeys
.static <T> java.lang.Iterable<T>
toIterable(java.util.Iterator<T> iterator)
Wraps anIterator
in anIterable
.static <T> java.util.List<T>
toList(java.util.Iterator<? extends T> iterator)
Returns a list that contains all the entries of the given iterator in the same order.static <T,K,V>
java.util.Map<K,V>toMap(java.util.Iterator<? extends T> inputs, Functions.Function1<? super T,K> computeKeys, Functions.Function1<? super T,V> computeValues)
Returns a map for which theMap.values()
are the product of invoking supplied functioncomputeValues
on input iterable elements, and each key is the product of invoking a supplied functioncomputeKeys
on same elements.static <K,V>
java.util.Map<K,V>toMap(java.util.Iterator<? extends V> values, Functions.Function1<? super V,K> computeKeys)
Returns a map for which theMap.values()
are the given elements in the given order, and each key is the product of invoking a supplied functioncomputeKeys
on its corresponding value.static <T> java.util.Set<T>
toSet(java.util.Iterator<? extends T> iterator)
Returns a set that contains all the unique entries of the given iterator in the order of their appearance.
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Method Detail
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toIterable
@Pure public static <T> java.lang.Iterable<T> toIterable(java.util.Iterator<T> iterator)
Wraps anIterator
in anIterable
. WARNING: The resultingIterable
may be used (e.g. callingIterableExtensions.isEmpty(Iterable)
) / iterated (e.g. in a for loop) only once. If you want to create a reusableIterable
callIterableExtensions.toList(Iterable)
orIterableExtensions.toSet(Iterable)
on the result and reuse the resultingList
/Set
- Parameters:
iterator
- theIterator
to wrap in anIterable
. May not benull
.- Returns:
- an
Iterable
providing the givenIterator
. Nevernull
.
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operator_plus
@Pure public static <T> java.util.Iterator<T> operator_plus(java.util.Iterator<? extends T> a, java.util.Iterator<? extends T> b)
Concatenates two iterators into a single iterator. The returned iterator traverses the elements in
a
, followed by the elements inb
. The resulting iterator is effectivly a view on the source iterators. That is, the source iterators are not polled until necessary and the result will reflect changes in the sources.The returned iterator supports
remove()
when the corresponding input iterator supports it.- Parameters:
a
- the first iterator. May not benull
.b
- the second iterator. May not benull
.- Returns:
- a combined iterator. Never
null
.
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findFirst
public static <T> T findFirst(java.util.Iterator<T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Finds the first element in the given iterator that fulfills the predicate. If none is found or the iterator is empty,null
is returned.- Parameters:
iterator
- the iterator. May not benull
.predicate
- the predicate. May not benull
.- Returns:
- the first element in the iterator for which the given predicate returns
true
, returnsnull
if no element matches the predicate or the iterator is empty.
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findLast
public static <T> T findLast(java.util.Iterator<T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Finds the last element in the given iterator that fulfills the predicate. If none is found or the iterator is empty,null
is returned.- Parameters:
iterator
- the iterator. May not benull
.predicate
- the predicate. May not benull
.- Returns:
- the last element in the iterator for which the given predicate returns
true
, returnsnull
if no element matches the predicate or the iterator is empty.
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head
public static <T> T head(java.util.Iterator<T> iterator)
Returns the first element in the given iterator ornull
if empty.- Parameters:
iterator
- the iterator. May not benull
.- Returns:
- the first element in the iterator or
null
.
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tail
public static <T> java.util.Iterator<T> tail(java.util.Iterator<T> iterator)
Returns a view on this iterator that contains all the elements except the first.- Parameters:
iterator
- the iterator. May not benull
.- Returns:
- an iterator with all elements except the first. Never
null
. - See Also:
drop(Iterator, int)
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last
public static <T> T last(java.util.Iterator<T> iterator)
Returns the last element in the given iterator ornull
if empty.- Parameters:
iterator
- the iterator. May not benull
.- Returns:
- the last element in the iterator or
null
.
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take
@Pure public static <T> java.util.Iterator<T> take(java.util.Iterator<T> iterator, int count)
Returns a view on this iterator that provides at most the firstcount
entries.- Parameters:
iterator
- the iterator. May not benull
.count
- the number of elements that should be returned at most.- Returns:
- an iterator with
count
elements. Nevernull
. - Throws:
java.lang.IllegalArgumentException
- ifcount
is negative.
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drop
public static <T> java.util.Iterator<T> drop(java.util.Iterator<T> iterator, int count)
Returns a view on this iterator that provides all elements except the firstcount
entries.- Parameters:
iterator
- the iterator. May not benull
.count
- the number of elements that should be dropped.- Returns:
- an iterator without the first
count
elements. Nevernull
. - Throws:
java.lang.IllegalArgumentException
- ifcount
is negative.
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exists
public static <T> boolean exists(java.util.Iterator<T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returnstrue
if one or more elements initerator
satisfy the predicate.Note that this will advance or even exhaust the given iterator.
- Parameters:
iterator
- the iterator. May not benull
.predicate
- the predicate. May not benull
.- Returns:
true
if one or more elements initerator
satisfy the predicate.
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forall
public static <T> boolean forall(java.util.Iterator<T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returnstrue
if every element initerator
satisfies the predicate. Ifiterator
is empty,true
is returned. In other words,false
is returned if at least one element fails to fulfill the predicate.- Parameters:
iterator
- the iterator. May not benull
.predicate
- the predicate. May not benull
.- Returns:
true
if every element initerator
satisfies the predicate and also if there is no element.
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filter
@Pure public static <T> java.util.Iterator<T> filter(java.util.Iterator<T> unfiltered, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returns the elements ofunfiltered
that satisfy a predicate. The resulting iterator does not supportremove()
. The returned iterator is a view on the original elements. Changes in the unfiltered original are reflected in the view.- Parameters:
unfiltered
- the unfiltered iterator. May not benull
.predicate
- the predicate. May not benull
.- Returns:
- an iterator that contains only the elements that fulfill the predicate. Never
null
.
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reject
@Pure public static <T> java.util.Iterator<T> reject(java.util.Iterator<T> unfiltered, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returns the elements ofunfiltered
that do not satisfy a predicate. The resulting iterator does not supportremove()
. The returned iterator is a view on the original elements. Changes in the unfiltered original are reflected in the view.- Parameters:
unfiltered
- the unfiltered iterator. May not benull
.predicate
- the predicate. May not benull
.- Returns:
- an iterator that contains only the elements that do not fulfill the predicate. Never
null
.
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filter
@Pure @GwtIncompatible("Class.isInstance") public static <T> java.util.Iterator<T> filter(java.util.Iterator<?> unfiltered, java.lang.Class<T> type)
Returns all instances of classtype
inunfiltered
. The returned iterator has elements whose class istype
or a subclass oftype
. The returned iterator does not supportremove()
. The returned iterator is a view on the original elements. Changes in the unfiltered original are reflected in the view.- Parameters:
unfiltered
- the unfiltered iterator. May not benull
.type
- the type of elements desired- Returns:
- an unmodifiable iterator containing all elements of the original iterator that were of the requested
type. Never
null
.
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filterNull
@Pure public static <T> java.util.Iterator<T> filterNull(java.util.Iterator<T> unfiltered)
Returns a new iterator filtering any null references.- Parameters:
unfiltered
- the unfiltered iterator. May not benull
.- Returns:
- an unmodifiable iterator containing all elements of the original iterator without any
null
references. Nevernull
.
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map
@Pure public static <T,R> java.util.Iterator<R> map(java.util.Iterator<T> original, Functions.Function1<? super T,? extends R> transformation)
Returns an iterator that performs the giventransformation
for each element oforiginal
when requested. The mapping is done lazily. The returned iterator's iterator supportsremove()
if the provided iterator does. After a successfulremove()
call,original
no longer contains the corresponding element.- Parameters:
original
- the original iterator. May not benull
.transformation
- the transformation. May not benull
.- Returns:
- an iterator that provides the result of the transformation. Never
null
.
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flatMap
@Pure public static <T,R> java.util.Iterator<R> flatMap(java.util.Iterator<T> original, Functions.Function1<? super T,? extends java.util.Iterator<R>> transformation)
Returns an iterable that performs the giventransformation
for each element oforiginal
when requested. The mapping is done lazily. That is, subsequent iterations of the elements in the iterable will repeatedly apply the transformation.The transformation maps each element to an iterable, and all resulting iterables are combined to a single iterable. Effectively a combination of
map(Iterator, Functions.Function1)
andflatten(Iterator)
is performed.The returned iterable's iterator does not support
remove()
in contrast tomap(Iterator, Functions.Function1)
.- Parameters:
original
- the original iterable. May not benull
.transformation
- the transformation. May not benull
and must not yieldnull
.- Returns:
- an iterable that provides the result of the transformation. Never
null
. - Since:
- 2.13
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flatten
public static <T> java.util.Iterator<T> flatten(java.util.Iterator<? extends java.util.Iterator<? extends T>> inputs)
Combines multiple iterators into a single iterator. The returned iterator traverses the elements of each iterator ininputs
. The input iterators are not polled until necessary.- Parameters:
inputs
- the to be flattened iterators. May not benull
.- Returns:
- an iterator that provides the concatenated values of the input elements. Never
null
. - Since:
- 2.13
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forEach
public static <T> void forEach(java.util.Iterator<T> iterator, Procedures.Procedure1<? super T> procedure)
Appliesprocedure
for each element of the given iterator.- Parameters:
iterator
- the iterator. May not benull
.procedure
- the procedure. May not benull
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forEach
public static <T> void forEach(java.util.Iterator<T> iterator, Procedures.Procedure2<? super T,? super java.lang.Integer> procedure)
Appliesprocedure
for each element of the given iterator. The procedure takes the element and a loop counter. If the counter would overflow,Integer.MAX_VALUE
is returned for all subsequent elements. The first element is at index zero.- Parameters:
iterator
- the iterator. May not benull
.procedure
- the procedure. May not benull
.
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join
public static java.lang.String join(java.util.Iterator<?> iterator)
Returns the concatenated string representation of the elements in the given iterator. No delimiter is used. The given iterator is left exhausted.- Parameters:
iterator
- the iterator. May not benull
.- Returns:
- the string representation of the iterator's elements. Never
null
. - See Also:
join(Iterator, CharSequence, org.eclipse.xtext.xbase.lib.Functions.Function1)
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join
public static java.lang.String join(java.util.Iterator<?> iterator, java.lang.CharSequence separator)
Returns the concatenated string representation of the elements in the given iterator. Theseparator
is used to between each pair of entries in the input. The stringnull
is used fornull
entries in the input. The given iterator is left exhausted.- Parameters:
iterator
- the iterator. May not benull
.separator
- the separator. May not benull
.- Returns:
- the string representation of the iterator's elements. Never
null
. - See Also:
join(Iterator, CharSequence, org.eclipse.xtext.xbase.lib.Functions.Function1)
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join
public static <T> java.lang.String join(java.util.Iterator<T> iterator, java.lang.CharSequence separator, Functions.Function1<? super T,? extends java.lang.CharSequence> function)
Returns the concatenated string representation of the elements in the given iterator. Thefunction
is used to compute the string for each element. Theseparator
is used to between each pair of entries in the input. The stringnull
is used if the function yieldsnull
as the string representation for an entry. The given iterator is left exhausted.- Parameters:
iterator
- the iterator. May not benull
.separator
- the separator. May not benull
.function
- the function that is used to compute the string representation of a single element. May not benull
.- Returns:
- the string representation of the iterator's elements. Never
null
.
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join
public static <T> java.lang.String join(java.util.Iterator<T> iterator, java.lang.CharSequence before, java.lang.CharSequence separator, java.lang.CharSequence after, Functions.Function1<? super T,? extends java.lang.CharSequence> function)
Returns the concatenated string representation of the elements in the given iterator. Thefunction
is used to compute the string for each element. Theseparator
is used to between each pair of entries in the input. The stringnull
is used if the function yieldsnull
as the string representation for an entry. The given iterator is left exhausted.- Parameters:
iterator
- the iterator. May not benull
.before
- prepends the resulting string if the iterator contains at least one element. May benull
which is equivalent to passing an empty string.separator
- the separator. May benull
which is equivalent to passing an empty string.after
- appended to the resulting string if the iterator contain at least one element. May benull
which is equivalent to passing an empty string.function
- the function that is used to compute the string representation of a single element. May not benull
.- Returns:
- the string representation of the iterator's elements. Never
null
.
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elementsEqual
public static boolean elementsEqual(java.util.Iterator<?> iterator, java.util.Iterator<?> other)
Determines whether two iterators contain equal elements in the same order. More specifically, this method returnstrue
ifiterator
andother
contain the same number of elements and every element ofiterator
is equal to the corresponding element ofother
.Note that this will advance or even exhaust the given iterators.
- Parameters:
iterator
- an iterator. May not benull
.other
- an iterator. May not benull
.- Returns:
true
if the two iterators contain equal elements in the same order.
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elementsEqual
public static boolean elementsEqual(java.util.Iterator<?> iterator, java.lang.Iterable<?> iterable)
Determines whether two iterators contain equal elements in the same order. More specifically, this method returnstrue
ifiterator
anditerable
contain the same number of elements and every element ofiterator
is equal to the corresponding element ofiterable
.Note that this will advance or even exhaust the given iterators.
- Parameters:
iterator
- an iterator. May not benull
.iterable
- an iterable. May not benull
.- Returns:
true
if the two iterators contain equal elements in the same order.
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isNullOrEmpty
public static boolean isNullOrEmpty(java.util.Iterator<?> iterator)
Determines if the given iterator isnull
or contains no elements.- Parameters:
iterator
- the to-be-queried iterator. May benull
.- Returns:
true
if the iterator isnull
or contains no elements
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isEmpty
public static boolean isEmpty(java.util.Iterator<?> iterator)
Determines if the given iterator contains no elements.- Parameters:
iterator
- the to-be-queried iterator. May not benull
.- Returns:
true
if the iterator contains no elements- See Also:
isNullOrEmpty(Iterator)
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size
public static int size(java.util.Iterator<?> iterator)
Returns the number of elements initerator
. The given iterator is left exhausted.- Parameters:
iterator
- the iterator. May not benull
.- Returns:
- the number of elements in
iterator
.
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reduce
public static <T> T reduce(java.util.Iterator<? extends T> iterator, Functions.Function2<? super T,? super T,? extends T> function)
Applies the combinator
function
to all elements of the iterator in turn.One of the function parameters is an element of the iterator, and the other is the result of previous application of the function. The seed of the operation is the first element in the iterator. The second value is computed by applying the function to the seed together with the second element of the iterator. The third value is computed from the previous result together with the third element and so on. In other words, the previous result of each step is taken and passed together with the next element to the combinator function.
If the iterator is empty,
null
is returned.More formally, given an iterator
[a, b, c, d]
and a functionf
, the result ofreduce
isf(f(f(a, b), c), d)
- Parameters:
iterator
- the to-be-reduced iterator. May not benull
.function
- the combinator function. May not benull
.- Returns:
- the last result of the applied combinator function or
null
for the empty input.
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fold
public static <T,R> R fold(java.util.Iterator<T> iterator, R seed, Functions.Function2<? super R,? super T,? extends R> function)
Applies the combinator
function
to all elements of the iterator in turn and usesseed
as the start value.One of the function parameters is an element of the iterator, and the other is the result of previous application of the function. The seed of the operation is explicitly passed to
fold
. The first computed value is the result of the applied function forseed
and the first element of the iterator. This intermediate result together with the second element of the iterator produced the next result and so on.fold
is similar toreduce
but allows aseed
value and the combinatorfunction
may be asymmetric. It takesT and R
and returnsR
.If the iterator is empty,
seed
is returned.More formally, given an iterator
[a, b, c, d]
, a seedinitial
and a functionf
, the result offold
isf(f(f(f(initial, a), b), c), d)
- Parameters:
iterator
- the to-be-folded iterator. May not benull
.seed
- the initial value. May benull
.function
- the combinator function. May not benull
.- Returns:
- the last result of the applied combinator function or
seed
for the empty input.
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toList
public static <T> java.util.List<T> toList(java.util.Iterator<? extends T> iterator)
Returns a list that contains all the entries of the given iterator in the same order.- Parameters:
iterator
- the iterator. May not benull
.- Returns:
- a list with the same entries as the given iterator. Never
null
.
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toSet
public static <T> java.util.Set<T> toSet(java.util.Iterator<? extends T> iterator)
Returns a set that contains all the unique entries of the given iterator in the order of their appearance. The result set is a copy of the iterator with stable order.- Parameters:
iterator
- the iterator. May not benull
.- Returns:
- a set with the unique entries of the given iterator. Never
null
.
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toInvertedMap
public static <K,V> java.util.Map<K,V> toInvertedMap(java.util.Iterator<? extends K> keys, Functions.Function1<? super K,V> computeValues)
Returns a map for which theMap.values()
are computed by the given function, and each key is an element in the givenkeys
. If the iterator contains equal keys more than once, the last one will be contained in the map. The map is computed eagerly. That is, subsequent changes in the keys are not reflected by the map. The key iterator is left exhausted.- Parameters:
keys
- the keys to use when constructing theMap
. May not benull
.computeValues
- the function used to produce the values for each key. May not benull
.- Returns:
- a map mapping each entry in the given iterator to the corresponding result when evaluating the function
computeValues
.
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toMap
public static <K,V> java.util.Map<K,V> toMap(java.util.Iterator<? extends V> values, Functions.Function1<? super V,K> computeKeys)
Returns a map for which theMap.values()
are the given elements in the given order, and each key is the product of invoking a supplied functioncomputeKeys
on its corresponding value. If the function produces the same key for different values, the last one will be contained in the map. The value iterator is left exhausted.- Parameters:
values
- the values to use when constructing theMap
. May not benull
.computeKeys
- the function used to produce the key for each value. May not benull
.- Returns:
- a map mapping the result of evaluating the function
keyFunction
on each value in the input iterator to that value
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toMap
public static <T,K,V> java.util.Map<K,V> toMap(java.util.Iterator<? extends T> inputs, Functions.Function1<? super T,K> computeKeys, Functions.Function1<? super T,V> computeValues)
Returns a map for which theMap.values()
are the product of invoking supplied functioncomputeValues
on input iterable elements, and each key is the product of invoking a supplied functioncomputeKeys
on same elements. If the function produces the same key for different values, the last one will be contained in the map. The input iterator is left exhausted.- Parameters:
inputs
- the elements to use when constructing theMap
. May not benull
.computeKeys
- the function used to produce the key for each value. May not benull
.computeValues
- the function used to produce the values for each key. May not benull
.- Returns:
- a map mapping the result of evaluating the functions
keyFunction
andcomputeValues
on each value in the input iterator to that value
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groupBy
public static <K,V> java.util.Map<K,java.util.List<V>> groupBy(java.util.Iterator<? extends V> values, Functions.Function1<? super V,? extends K> computeKeys)
Returns a map for which theMap.values()
is a collection of lists, where the elements in the list will appear in the order as they appeared in the iterator. Each key is the product of invoking the supplied functioncomputeKeys
on its corresponding value. So a key of that map groups a list of values for which the function produced exactly that key. The value iterator is left exhausted.- Parameters:
values
- the values to use when constructing theMap
. May not benull
.computeKeys
- the function used to produce the key for each value. May not benull
.- Returns:
- a map mapping the result of evaluating the function
keyFunction
on each value in the input iterator to that value. As there can be more than one value mapped by a key, the mapping result is is a list of values. - Since:
- 2.7
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takeWhile
public static <T> java.util.Iterator<T> takeWhile(java.util.Iterator<? extends T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returns an Iterator containing all elements starting from the head of the source up to and excluding the first element that violates the predicate. The resulting Iterator is a lazily computed view, so any modifications to the underlying Iterators will be reflected on iteration. The result does not supportIterator.remove()
- Parameters:
iterator
- the elements from which to take. May not benull
.predicate
- the predicate which decides whether to keep taking elements. May not benull
.- Returns:
- the taken elements
- Since:
- 2.7
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dropWhile
public static <T> java.util.Iterator<T> dropWhile(java.util.Iterator<? extends T> iterator, Functions.Function1<? super T,java.lang.Boolean> predicate)
Returns an Iterator containing all elements starting from the first element for which the drop-predicate returned false. The resulting Iterator is a lazily computed view, so any modifications to the underlying Iterators will be reflected on iteration. The result does not supportIterator.remove()
- Parameters:
iterator
- the elements from which to drop. May not benull
.predicate
- the predicate which decides whether to keep dropping elements. May not benull
.- Returns:
- the remaining elements after dropping
- Since:
- 2.7
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indexed
public static <A> java.util.Iterator<Pair<java.lang.Integer,A>> indexed(java.util.Iterator<? extends A> iterator)
Returns an Iterator of Pairs where the nth pair is created by taking the nth element of the source as the value and its 0-based index as the key. E.g.zipWitIndex(#["a", "b", "c"]) == #[(0, "a"), (1, "b"), (2, "c")]
If the index would overflow,Integer.MAX_VALUE
is returned for all subsequent elements. The resulting Iterator is a lazily computed view, so any modifications to the underlying Iterator will be reflected on iteration. The result does not supportIterator.remove()
- Parameters:
iterator
- the elements. May not benull
.- Returns:
- the zipped result
- Since:
- 2.7
-
min
public static <T extends java.lang.Comparable<? super T>> T min(java.util.Iterator<T> iterator)
Finds the minimum of the given elements according to their natural ordering. If there are several mimina, the first one will be returned.Note that this will advance or even exhaust the given iterator.
- Parameters:
iterator
- the mutually comparable elements. May not benull
.- Returns:
- the minimum
- Throws:
java.util.NoSuchElementException
- if the iterator is empty- Since:
- 2.7
-
minBy
public static <T,C extends java.lang.Comparable<? super C>> T minBy(java.util.Iterator<T> iterator, Functions.Function1<? super T,C> compareBy)
Finds the element that yields the minimum value when passed tocompareBy
. If there are several maxima, the first one will be returned.Note that this will advance or even exhaust the given iterator.
- Parameters:
iterator
- the elements to find the minimum of. May not benull
.compareBy
- a function that returns a comparable characteristic to compare the elements by. May not benull
.- Returns:
- the minimum
- Throws:
java.util.NoSuchElementException
- if the iterator is empty- Since:
- 2.7
-
min
public static <T> T min(java.util.Iterator<T> iterator, java.util.Comparator<? super T> comparator)
Finds the mininmum element according tocomparator
. If there are several minima, the first one will be returned.Note that this will advance or even exhaust the given iterator.
- Parameters:
iterator
- the elements to find the minimum of. May not benull
.comparator
- the comparison function. May not benull
.- Returns:
- the minimum
- Throws:
java.util.NoSuchElementException
- if the iterator is empty- Since:
- 2.7
-
max
public static <T extends java.lang.Comparable<? super T>> T max(java.util.Iterator<T> iterator)
Finds the maximum of the elements according to their natural ordering. If there are several maxima, the first one will be returned.Note that this will advance or even exhaust the given iterator.
- Parameters:
iterator
- the mutually comparable elements. May not benull
.- Returns:
- the maximum
- Throws:
java.util.NoSuchElementException
- if the iterator is empty- Since:
- 2.7
-
maxBy
public static <T,C extends java.lang.Comparable<? super C>> T maxBy(java.util.Iterator<T> iterator, Functions.Function1<? super T,C> compareBy)
Finds the element that yields the maximum value when passed tocompareBy
If there are several maxima, the first one will be returned.Note that this will advance or even exhaust the given iterator.
- Parameters:
iterator
- the elements to find the maximum of. May not benull
.compareBy
- a function that returns a comparable characteristic to compare the elements by. May not benull
.- Returns:
- the maximum
- Throws:
java.util.NoSuchElementException
- if the iterator is empty- Since:
- 2.7
-
max
public static <T> T max(java.util.Iterator<T> iterator, java.util.Comparator<? super T> comparator)
Finds the maximum element according tocomparator
. If there are several maxima, the first one will be returned.Note that this will advance or even exhaust the given iterator.
- Parameters:
iterator
- the elements to find the maximum of. May not benull
.comparator
- the comparison function. May not benull
.- Returns:
- the maximum
- Throws:
java.util.NoSuchElementException
- if the iterator is empty- Since:
- 2.7
-
contains
public static boolean contains(java.util.Iterator<?> iterator, java.lang.Object o)
Returns true if this Iterator contains the specified element. More formally, returns true if and only if this Iterator contains at least one element e such that (o==null ? e==null : o.equals(e)).Note that this will advance or even exhaust the given iterator.
- Parameters:
iterator
- the elements to testo
- element whose presence in this Iterator is to be tested- Returns:
- true if this Iterator contains the specified element
-
-